Patent Application
20240236612
The present invention concerns electroacoustic and in particular concepts for generating and reproducing audio signals in a space, such as in a vehicle or a stationary space, such as a hall, a waiting area, etc.
Typically, acoustic scenes are recorded using a set of microphones. Each microphone outputs a microphone signal. For example, 25 microphones may be used for an audio scene of an orchestra. A sound engineer then mixes the 25 microphone output signals, e.g., into a standard format such as a stereo format, a 5.1 format, a 7.1 format, a 7.2 format, or any other corresponding format. In case of a stereo format, e.g., the sound engineer or an automatic mixing process generates two stereo channels. In the case of a 5.1 format, mixing results in five channels and one subwoofer channel. Analogously, in case of a 7.2 format, e.g., mixing results in seven channels and two subwoofer channels. If the audio scene is to be rendered in a reproduction environment, a mixing result is applied to electrodynamic loudspeakers. In a stereo reproduction scenario, there are two loudspeakers, the first loudspeaker receiving the first stereo channel and the second loudspeaker receiving the second stereo channel. For example, in a 7.2 reproduction format, there are seven loudspeakers at predetermined positions, and two subwoofers, which can be placed relatively arbitrarily. The seven channels are applied to the corresponding loudspeakers, and the subwoofer channels are applied to the corresponding subwoofers.
The use of a single microphone arrangement when capturing audio signals, and the use of a single loudspeaker arrangement when reproducing the audio signals typically neglects the true nature of the sound sources. European patent EP 2692154 B1 describes a set for capturing and reproducing an audio scene, in which not only the translation but also the rotation and, in addition, the vibration is captured and reproduced. Thus, a sound scene is not only reproduced by a single capturing signal or a single mixed signal but by two capturing signals or two mixed signals that, on the one hand, are recorded simultaneously, and that, on the other hand, are reproduced simultaneously. This ensures that different emission characteristics of the audio scene are recorded compared to a standard recording, and are reproduced in a reproduction environment.
To this end, as is illustrated in the European patent, a set of microphones is placed between the acoustic scene and a (imaginary) listener space to capture the “conventional” or translation signal that is characterized by a high directionality, or high quality.
In addition, a second set of microphones is placed above or to the side of the acoustic scene to record a signal with lower quality, or lower directionality, that is intended to represent the rotation of the sound sources in contrast to the translation.
On the reproduction side, corresponding loudspeakers are placed at the typical standard positions, each of which has a omnidirectional arrangement to reproduce the rotation signal, and a directional arrangement to reproduce the “conventional” translational sound signal. In addition, there is a subwoofer at each of the standard positions, or there is only a single subwoofer at an arbitrary location.
European patent EP 2692144 B1 discloses a loudspeaker for reproducing, on the one hand, the translational audio signal and, on the other hand, the rotatory audio signal. Thus, the loudspeaker has, on the one hand, an arrangement that emits in an omnidirectional manner, and, on the other hand, an arrangement that emits in a directional manner.
European patent EP 2692151 B1 discloses an electret microphone that can be used for recording the omnidirectional or the directional signal.
European patent EP 3061262 B1 discloses earphones and a method for manufacturing earphones that generate both a translational sound field and a rotatory sound field.
European patent EP 3061266 B1 discloses earphones and a method for producing earphones configured to generate the “conventional” translational sound signal by using a first transducer, and to generate the rotatory sound field by using a second transducer arranged perpendicular to the first transducer.
Recording and reproducing the rotatory sound field in addition to the translational sound field leads to a significantly improved and therefore high-quality audio signal perception that almost conveys the impression of a live concert, even though the audio signal is reproduced by the loudspeaker or headphones or earphones.
This achieves a sound experience that can almost not be distinguished from the original sound scene in which the sound is not emitted by loudspeakers but by musical instruments or human voices. This is achieved by considering that the sound is emitted not only translationally but also in a rotary manner and possibly also in a vibrational manner, and is therefore to be recorded and reproduced accordingly.
A disadvantage of the concept described is that recording the additional signal that reproduces the rotation of the sound field represents a further effort. In addition, there are many pieces of music, for example classical pieces or pop pieces, where only the conventional translational sound field has been recorded. Typically, the data rate of these pieces is heavily compressed, e.g., according to the MP3 standard or the MP4 standard, contributing to an additional deterioration of quality, however, which is typically only audible for experienced listeners. On the other hand, there are almost no audio pieces that have not been recorded at least in the stereo format, i.e. with a left channel and a right channel. Rather, the development goes towards generating more channels than only a left and a right channel, i.e. generating surround recordings with five channels or even recordings with higher formats, for example, which is known under the keyword MPEG surround or Dolby Digital in the technology.
Thus, there are many pieces that have been recorded at least in the stereo format, i.e. with a first channel for the left side and a second channel for the right side. There are even more and more pieces where recording has been done with more than two channels, e.g., for a format with several channels on the left side and several channels on the right side and one channel in the center. Even higher level formats use more than five channels in the horizontal plane and in addition also channels from above or channels from obliquely above and possibly also, if possible, channels from below.
However, these formats all have in common that they only reproduce the conventional translatory sound by applying the individual channels to corresponding loudspeakers with corresponding transducers.
An embodiment may have an apparatus for generating control signals for a loudspeaker system with two sound generators, comprising: a first input for a first channel signal of a multi-channel audio signal; a second input for a second channel signal of the multi-channel audio signal; a first output for a first control signal for a first sound generator; a second output for a second control signal for a second sound generator; a base differential mode signal generator for forming a base differential mode signal from the first channel signal and the second channel signal at the second input; a differential mode signal generator for generating a first differential mode signal and a second differential mode signal from the base differential mode signal, wherein the first differential mode signal is phase-shifted with respect to the second differential mode signal; and a mixer for mixing a common mode signal with the first differential mode signal so as to acquire the first control signal, and for mixing the common mode signal with the second differential mode signal so as to acquire the second control signal, wherein the differential mode signal generator comprises: a frequency filter for generating one or several low-pass signals from one input signal or several input signals in the frequency filter; and spectral interlacer for spectrally filtering the one low-pass signal or a first low-pass signal of the several low-pass signals in a first manner so as to acquire a first filtered signal, and the one low-pass signal or a second low-pass signal of the several low-pass signals in a second manner so as to acquire the second filtered signal that differs from the first filtered signal, wherein the differential mode signal generator is configured to use the first filtered signal as the first differential mode signal or to derive the first differential mode signal from the first filtered signal, or to use the second filtered signal as the second differential mode signal or to derive the second differential mode signal from the second filtered signal.
Another embodiment may have a method for generating control signals to a loudspeaker system with two sound generators, comprising: receiving a first channel signal of a multi-channel audio signal and a second channel signal of a multi-channel audio signal; outputting a first control signal for the first sound generator, and a second control signal for the second sound generator; forming a base differential mode signal from the first channel signal and the second channel signal; generating a first differential mode signal and a second differential mode signal from the base differential mode signal, wherein the first differential mode signal is phase-shifted with respect to the second differential mode signal; and mixing a common mode signal with the first differential mode signal so as to acquire the first control signal, and for mixing the common mode signal with the second differential mode signal so as to acquire the second control signal, wherein generating comprises: generating one or several low-pass signals from one input signal or several input signals in the frequency filter; and spectrally filtering the one low-pass signal or a first low-pass signal of the several low-pass signals in a first manner so as to acquire a first filtered signal, and the one low-pass signal or a second low-pass signal of the several low-pass signals in a second manner so as to acquire the second filtered signal that differs from the first filtered signal, wherein the first filtered signal is used as the first differential mode signal or the first differential mode signal is derived from the first filtered signal, and wherein the second filtered signal is used as the second differential mode signal or the second differential mode signal is derived from the second filtered signal.
Another embodiment may have a non-transitory digital storage medium having a computer program stored thereon to perform the method for generating control signals to a loudspeaker system with two sound generators, comprising: receiving a first channel signal of a multi-channel audio signal and a second channel signal of a multi-channel audio signal; outputting a first control signal for the first sound generator, and a second control signal for the second sound generator; forming a base differential mode signal from the first channel signal and the second channel signal; generating a first differential mode signal and a second differential mode signal from the base differential mode signal, wherein the first differential mode signal is phase-shifted with respect to the second differential mode signal; and mixing a common mode signal with the first differential mode signal so as to acquire the first control signal, and for mixing the common mode signal with the second differential mode signal so as to acquire the second control signal, wherein generating comprises: generating one or several low-pass signals from one input signal or several input signals in the frequency filter; and spectrally filtering the one low-pass signal or a first low-pass signal of the several low-pass signals in a first manner so as to acquire a first filtered signal, and the one low-pass signal or a second low-pass signal of the several low-pass signals in a second manner so as to acquire the second filtered signal that differs from the first filtered signal, wherein the first filtered signal is used as the first differential mode signal or the first differential mode signal is derived from the first filtered signal, and wherein the second filtered signal is used as the second differential mode signal or the second differential mode signal is derived from the second filtered signal, when said computer program is run by a computer.
An inventive apparatus for generating control signals for a loudspeaker system with two sound generators includes: a first input for a first channel signal of a multi-channel audio signal; a second input for a second channel signal of the multi-channel audio signal; a first output for a first control signal for a first sound generator; a second output for a second control signal for a second sound generator; a base differential mode signal generator for forming a base differential mode signal of the first channel signal at the first input and of the second channel signal at the second input; a differential mode signal generator for generating a first differential mode signal and a second differential mode signal from the base differential mode signal, wherein the first differential mode signal is phase-shifted with respect to the second differential mode signal; and a mixer for mixing a common mode signal with the first differential mode signal so as to obtain the first control signal, and for mixing the common mode signal with the second differential mode signal so as to obtain the second control signal, wherein the differential mode signal generator comprises: a frequency filter for generating one or several low-pass signals from an input signal or several input signals in the frequency filter; and spectral interlacing means (or spectral interlacer, or spectral processor) for spectrally filtering the one low-pass signal or a first low-pass signal of the several low-pass signals in a first manner so as to obtain a first filtered signal, and the one low-pass signal or a second low-pass signal of the several low-pass signals in a second manner so as to obtain a second filtered signal that differs from the first filtered signal, wherein the differential mode signal generator is configured to use the first filtered signal as the first differential mode signal or to derive the first differential mode signal from the first filtered signal, and to use the second filtered signal as the second differential mode signal or to derive the second differential mode signal from the second filtered signal.
Advantageously, the lowest spectral range is supplied to the spectral interlacing means. This range is also referred to as low-pass signal. The center spectral range, advantageously adjacent to the lowest range, is not subjected to spectral interlacing. Instead, this range, which is contained in a signal referred to as high-pass signal, is used directly without interlacing filtering so as to generate the differential mode signals. The high spectral range is advantageously also not subjected to spectral interlacing processing, but may be used directly for the utilization of the differential mode signal. Alternative, however, only a common mode signal is emitted in the upper range, so that one tweeter suffices here. Alternative, however, two tweeters with a differential mode signal control may be provided.
According to the invention, only the low-pass range of the base differential mode signal (prior to the phase shift) or of two phase-shifted base differential mode signals is subjected to spectral interlacing, whereas the higher frequency range of the control signal for the midrange speakers or woofers is not subjected to spectral interlacing, but is directly guided to the sound generators so as to here generate a non-spectrally filtered differential mode signal. Spectral interlacing in the low frequency range ensures that the two differential mode signals do not cancel each other out in the air even though they are phase-shifted. This could happen if the size of the sound transducers of the midrange speakers or woofers, or their distance, is not large enough. Since there are construction boundaries in this regard, it is advantageous to perform corresponding spectral interlacing of the first differential mode signal with respect to the second differential mode signal in the low-pass range obtained by the frequency filter. In contrast, it has been found that such spectral interlacing in the treble range of the base differential mode signal should not be carried out, since the construction conditions of the two midrange speakers or woofers and the geometrical arrangement and the geometrical distance are sufficient so that the differential mode propagates in the air excited by the loudspeaker system.
The apparatus for generating control signals includes a base differential mode signal generator, possibly a common mode signal generator, a differential mode signal generator, a mixer, and possibly a tweeter signal generator so as to identify two or three control signals, respectively.
The common mode signal generator and the tweeter signal generator advantageously include a frequency filter to generate from the original signal a low-pass signal that is required for the common mode signal generation, and to further generate a high-pass signal required for the tweeter signal generator. Furthermore, in advantageous embodiments, the differential mode signal generator includes a further frequency filter to generate a high-pass signal and a low-pass signal, wherein the high-pass signal is not further filtered spectrally in the differential mode signal generator. On the other hand, the low-pass signal is provided to spectral interlacing means so as to achieve spectral interlacing to the effect that the low, or bass, portions emitted by the two midrange speakers or woofers do not cancel each other out. Thus, spectral interlacing in the two control signals with respect to each other is achieved through the spectral interlacing means, however, limited to the base range, since the high-pass range of the control signal is ideally radiated for the midrange speakers or woofers, or the sound generator in general, due to the geometry of the midrange speakers or woofers, and, therefore, no cancellation is to be expected in the sound transfer medium.
Advantageously, the signal for the tweeter is not processed with respect to the a differential mode signal processing. Instead, the signal radiated by the tweeter will be purely a common mode signal, however, according to the implementation, which will be supplemented by an accordingly amplified or attenuated differential signal portion. However, since there is only one tweeter, only one common mode signal will be excited in the sound propagation medium. On the other hand, due to the inventive control, the two midrange speakers or woofers simultaneously excite the common mode and the push/pull mode, or differential mode, in the sound transfer medium, leading to the excellent perceived sound quality in the space to be acoustically irradiated.
According to the embodiment, the inventive apparatus further includes an interface for transmitting the control signals. The interface may be configured in a wired or a wireless manner and, according to the implementation, it may already include power amplifiers or not.
In addition, according to the implementation, the interface may perform further measures for the control signals, such as equalizer processing of the signals or source coding of the signals or source coding and transmitter processing of the signals so as to transmit the signals, e.g. wirelessly by means of a wireless protocol such as Bluetooth or DECT, to an input interface of a loudspeaker module typically also comprising power amplifiers.
Embodiments are based on the finding that, by generating a first and a second differential signal both derived from the first channel signal, from the second channel signal, or from both channel signals, a differential wave field may be generated around the two midrange speakers or woofers and therefore for a person acoustically irradiated by the loudspeakers, said differential wave field representing, in addition to the translational sound output by the loudspeakers, also the rotatory sound leading to a significant quality improvement of the subjective audio perception. In particular, separate loudspeakers are not required for the generation of the differential sound field, but the differential sound field is generated by accordingly applying, to the control signals for the loudspeakers, signals that have a phase difference with respect to each other, wherein this phase difference is advantageously 180°, however, it may be in the range 160° and 200°, which almost obtains the same effect as if the signals have the advantageously best phase shift of 180°.
The closer the first and the second midrange speakers or woofers are arranged with respect to each other, the better the effect of the differential wave field. The loudspeakers should be spaced apart from each other advantageously at least 10 cm and at most 1 m, wherein distances are advantageous in the range of 20 cm (e.g. 15 to 30 cm). The relatively close spatial arrangement of the two loudspeakers particularly achieves that no separate sound generators are required for the generation of the differential wave field. Instead, it is sufficient that the two midrange speakers or woofers obtain the special inventive control signals.
Only one channel signal, i.e. either the left channel signal or the right channel signal, may be used to generate the control signal. Alternatively, a sum of the two channel signals, i.e. a mono signal, may be used. Alternatively and advantageously, the calculation of the base differential mode signal is based on taking between the two channel signals a difference which the base differential mode signal or the differential mode signals or mixed signals dominates. According to the implementation, this difference may be used directly, or it or may be combined with a sum signal, or it may be combined with the left channel signal or the right channel signal. However, it is advantageous to either use the differential signal alone for calculating the base differential mode signal or the mixed signals, or to use the differential signal in combination with the sum signal of the two channels, wherein the proportion of the differential signal and the proportion of the sum signals in the final differential mode signals or mixed signals is adjustable, and is advantageously set such that the differential signal determines at least ⅔ of the two differential mode signals or mixed signals with respect to the corresponding energy in the signals.
The loudspeakers are advantageously installed in a space such as an interior space in a vehicle, e.g. a land vehicle (car, train, sled, motor vehicle, . . . ), an air vehicle (“passenger” aircraft, helicopters, zeppelin, etc.), a water vehicle (boat, ferry, yacht, sailboard, etc.) or a space craft.
The two sound generators, such as the midrange speakers or woofers, generate differential soundwave fields. They may be generated via an oscillating surface (planar transducer) nor via two neighboring piston converters (loudspeakers) oscillating in the differential mode, or via other described transducers. Mono signals and/or differential signals (L-R or R-L) may serve as source signals for the generation of the differential soundwave field.
A synthetic generation of the rotation signal is possible if there is an audio piece with more than one channel, i.e. already having two, e.g. stereo, channels or even more channels. According to the invention, calculating an at least approximate difference obtains at least an approximation with respect to the differential signal, or rotation signal, which may then be used to drive the respective loudspeakers together with the respective channel signal. To this end, a calculation of two mix signals having a phase difference with respect to each other is performed.
In a further embodiment, in which there are more than two channels, e.g. in case of a 5.1 signal, a down mixer for the first channel signal, e.g., i.e. for the left channel, and a further down mixer for the second channel signal (i.e. for the right channel) are connected upstream of the control signal generator. However, if the signal is available as an original microphone signal, such as an ambisonics signal with several components, each down mixer is configured to accordingly calculate, from the ambisonics signal, a left channel or a right channel which is then used by the control signal generator to calculate the control signals.
According to a first aspect of the present invention, the loudspeakers are arranged separately from the apparatus for generating control signals. In such an embodiment, the loudspeakers have signal inputs that may be wired or wireless, wherein a signal for a sound generator in the loudspeaker is generated at each signal input. The control signal generator providing the control signals for the sound generator is arranged away from the actual loudspeaker and is connected to the loudspeakers via a communication link such as a wired connection or a wireless connection.
In another embodiment, the control signal generator is integrated into the loudspeakers or into a loudspeaker or into the vehicle. In such a case, in the loudspeaker with an integrated signal processor, the common mode signal is derived, and, depending on the implementation and the embodiment, the differential mode signal is derived separately, or is derived from the common mode signal. An aspect of the present invention therefore concerns the loudspeaker without a signal processor. Another aspect of the present invention therefore concerns the signal processor without a loudspeaker, and a further aspect of the present invention concerns the loudspeaker with an integrated signal processor.
Embodiments of the present invention will be detailed subsequently referring to the appended drawings, in which:
A number of further embodiments are illustrated with reference to
According to the embodiment, the spectral interlacing means may only obtain a low-pass signal and generate therefrom both spectrally filtered signals, as it is exemplarily illustrated in
A loudspeaker system includes at least two sound generators that may be arranged in spatial proximity. A advantageous loudspeaker system includes two midrange speakers or woofers that can be controlled separately and that essentially comprise equally sized membranes, as well as a tweeter. The two midrange speakers or woofers as well as the tweeter are accommodated in a loudspeaker housing, wherein the tweeter, same as the midrange speakers or woofers, is arranged in the loudspeaker housing and is mounted between the two midrange speakers or woofers.
This loudspeaker system, or loudspeaker module, is particularly suitable for an instrument panel or a rear shelf, or for a corresponding area in a vehicle, however, it may also be used to acoustically irradiate stationary spaces. In particular, the two midrange speakers or woofers are configured to provide an acoustic irradiation in a vehicle, or in a space to be acoustically irradiated, not only with the common-mode signal, i.e. the conventional audio channel, which may be a left channel, a right channel, a left rear channel, a right rear channel, or a center channel. Instead, in addition to the common mode (CM), the two midrange speakers or woofers also provide a push/pull mode, or differential mode (DM). According to the invention, this achieves a special sound experience, since the loudspeaker module does not only generate the common mode but also the differential mode and therefore does not only excite translational sound but also rotatory sound in the air. The tweeter is arranged between the two loudspeakers so as to provide efficient space utilization of the loudspeaker system housing and, on the other hand, so as to also achieve an optimum spatial source for the sound that is excited by the tweeter to the effect that the tweeter sound is excited close to the common mode or the differential mode of the two midrange speakers or woofers.
Advantageously, the loudspeaker module is a flat module, in particular for installation in an instrument panel or a rear shelf or any other corresponding position in a vehicle, wherein the top side of the loudspeaker housing has a length or width that is at least twice as large as the height of the loudspeaker system housing. Furthermore, in advantageous embodiments, the tweeter and the two midrange speakers or woofers each include a membrane that is essentially deflectable perpendicular to a top side of a loudspeaker system housing. In an alternative embodiment in the form of a shelf loudspeaker, the two midrange speakers or woofers and the tweeter are also arranged, however, in a housing that advantageously stands upright. The two membranes of the midrange speakers or woofers are arranged such that they are parallel and excite the sound in the same direction, i.e. perpendicular to a membrane surface. In addition, the tweeter is again advantageously arranged between the first and the second membrane, however, it is now deflectable essentially perpendicular to the two membranes so that, if the three loudspeakers are operated simultaneously, the membranes of the tweeter vibrates essentially perpendicular to the membranes of the two midrange speakers or woofers.
In advantageous embodiments, the loudspeaker modules for the instrument panel or the rear shelf are arranged at different positions, such as on the left, in the center, or on the right, wherein, depending on the implementation, there are different combinations with simple loudspeakers that irradiate the common mode signal only, i.e. the left channel or the right channel or any other channel, however without differential mode. Thus, there are different combinations of the inventive loudspeaker module with conventional loudspeakers to the effect that the effort for the acoustic irradiation may be reduced according to the requirement, or is kept at a maximum level in the sense of a best possible acoustic irradiation result, while an inventive loudspeaker module is used on the left side, in the center, and on the right side.
Both, the loudspeaker module to be installed in a vehicle and the loudspeaker system configured as a shelf loudspeaker are advantageously controlled with the inventive apparatus, which is also referred to as a control circuit, configured to generate the control signals for the three elementary loudspeakers, i.e. the two midrange speakers or woofers and the tweeter, from at least two channel signals of a multi-channel audio signal. This apparatus for generating control signals is either configured to be integrated into the loudspeaker module or into the shelf loudspeaker, or into any other loudspeaker system with two loudspeakers, or is arranged separately from the loudspeaker system, or the loudspeaker system housing. In the first case, only the two channel signals of the multi-channel audio signal have to be supplied to the loudspeaker system housing, and the apparatus for generating control signals generates the three control signals for the individual elementary loudspeaker internally, i.e. in the loudspeaker system housing. In this case, amplification means in the form of an individual audio amplifier, e.g. for each control signal, are advantageously provided in the loudspeaker housing. In an alternative embodiment in which the apparatus for generating control signals is configured separately, the apparatus for generating control signals includes an input interface to obtain the two channel signals. In this case, the apparatus for generating control signals is advantageously configured as an app, bit or as a hardware element in a mobile device such as a mobile telephone, a tablet, etc. Furthermore, an output interface is provided so as to transfer the control signals in a fully conditioned manner either wirelessly or in a wired way, however, advantageously not amplified, to the loudspeaker housing which in turn has an input interface to receive the control signals, and which further comprises an amplifier stage to accordingly amplify the respective control signals.
A separate arrangement of the amplifier stage outside of the loudspeaker system housing is possible, wherein, in this case, cables are advantageously provided between the amplifier stage and the loudspeaker system housing so as to provide the amplified control signals to the corresponding elementary loudspeakers, i.e. the tweeter and the midrange speakers or woofers in the loudspeaker system housing.
However, for reasons of spatial efficiency, as is shown in
In the embodiment shown in
This enables achieving a flat loudspeaker module that may be housed in an instrument panel, or a rear shelf, or any other flat possibility for installation, such as a door or a side panel in a vehicle. A loudspeaker system as shown in
The schematic illustration shown in
Version B shows a reduced effort version, wherein only the center loudspeaker system is configured to emit the common mode and the differential mode, whereas the two loudspeaker systems on the left and the right side only comprise a single midrange speaker or woofer that emits only the common mode signal, or the common mode.
Version C shows an implementation without a center loudspeaker, wherein a loudspeaker system according to the present invention is arranged only on the left side and the right side, said loudspeaker system emitting in such a way the common mode and the differential mode in the midrange and the bass range, whereas the tweeter only emits a common mode signal, since it operates with a single sound transducer only. However, it has been found that an emission of just the common mode signal is sufficient for the excellent sound quality of the present invention, and that an additional implementation of the tweeter with a common mode signal does not lead to a significant improvement of the sound quality, which is why the effort required to this end may be omitted, in contrast to the case in which two tweeters would be used for the treble range.
Version D shows a further implementation, having the configuration selected in version C, however, wherein, for support of the center signal, a simple sound transducer is additionally provided to emit the center signal that is typically a mono signal obtained by addition of the left and the right side, or which is available separately in the multi-channel audio signal.
Version A of
Thus, in the present invention, a differential mode is not generated in the treble range since this does not lead to any significant improvement of the perceived sound field. In the mid frequency range, i.e. in the high-pass range of the midrange or bass signal, an unprocessed common mode signal is generated that has not been subjected to any spectral interlacing so as to generate and to perceive in the midrange, which is particularly important for the perception, the entire differential mode signal, or the entire differential mode component in the sound field. Spectral interlacing is only carried out in the low spectral range, i.e. in the low-pass range of the base differential mode signal, to ensure that a sufficiently strong differential mode component is also perceived in the low frequency range, which is also important for the perception of a differential mode component. The means for spectral interlacing therefore makes it possible to achieve a good perception of the differential mode component even in the area in which the constructive circumstances of the loudspeaker system are no longer optimal.
In the embodiment shown in
The phase shifter 531 has connected downstream thereof a frequency filter 532 configured to filter the first phase-shifted signal so as to obtain a first high-pass signal and a first low-pass signal. Furthermore, the frequency filter 532 is configured to filter the second phase-shifted signal with respect to its frequency so as to obtain a second low-pass signal and a second high-pass signal. The two low-pass signals generated by the frequency filter 532 are supplied to the spectral interlacing means 533, which applies a first spectral filter to the first low-pass signal and a second spectral filter to the second low-pass filter to the extent that the two output signals of the spectral interlacing means 533 are different. Advantageously, the signals are different in that both signals comprise frequency portions that are complimentary with respect to each other, i.e. so that the first spectral filter attenuates in a first range in which the second spectral filter has a passthrough range, and vice versa. The first spectral filter does not necessarily have to fully attenuate in a range in which the spectral filter has a passthrough range. However, instead, it is already sufficient that a certain attenuation is achieved, such as at least 3 dB, and advantageously at least 6 dB, with respect to the signal power. Thus, filters that are not overly elaborate, particularly bandpass filters, are sufficient for the first spectral filtering and the second spectral filtering to the extent that a bandpass filter has an attenuation of around 6 dB for the first low-pass signal in a spectral range in which the second spectral filter has a bandpass that here has a passthrough range and comprises none or only little attenuation.
In addition, in the embodiment shown in
However, if a combination of the filtered low-pass signal and the corresponding high-pass signal is carried out, e.g. by means of a filterbank, and the common mode signal GLTS is present in the time domain, the mix in the mixer would first include the filterbank so as to generate from the high-pass signal and the corresponding filtered low-pass signal the corresponding complete differential mode signal that is then combined with the common mode signal also present in the time domain by means of a time domain adder that carries out sample-wise addition, for example.
In the embodiment shown in
However, if the implementation shown in
The passthrough ranges of the corresponding filters are schematically illustrated in
Further implementations are shown in
There are further possibilities to generate a base differential mode signal, wherein a rotating sound field component is generated, since the first differential mode signal and the second differential mode signal are overlapped with the common mode signal so that the two midrange or woofer sound generators in the loudspeaker system perform a differential mode signal excitation that is perceivable as a rotating sound field. Depending on the particular generation of the differential mode signal, the rotating sound field will correspond more strongly to the original physical rotating sound field. It has been found that a derivation of the differential mode signal from the common mode signal and a corresponding overlap by means of the mixer 540 of
The two bandpass filter implementations 320a, b, c, 340a, b of
In the embodiment shown in
The embodiment of the loudspeaker system is advantageously combined with the differential mode signal generation in which the two differential mode signals for the two midrange or woofer sound generators are generated by using interlaced bandpasses so that the frequency content of the one differential mode signal is essentially interlaced with respect to the frequency content of the other differential mode signal. However, it is to be noted that interlaced may here be understood as approximately interlaced, since bandpass filters comprise overlaps between neighboring channels, since bandpass filters with a very steep edge cannot be implemented, or only with great effort. A bandpass implementation as is schematically illustrated in
Subsequently, further advantageous implementations of the control circuit as illustrated in
In
The high-pass cutoff frequency for forming the tweeter control signal, i.e. for forming the third control signal, is advantageously 4 kHz, however, may be in the range of between 3 kHz and 5 kHz. Accordingly, the low-pass cutoff frequency of the low-pass 521 for forming the common mode signal 529 may also be correspondingly set to the high-pass cutoff frequency, e.g. at 4 kHz, or is in a range of between 3 kHz and 5 kHz.
In addition, the low-pass or high-pass cutoff frequency for the frequency filter 532 in the differential mode signal generator 530 is accordingly lower, i.e. advantageously at 200 Hz. Depending on the implementation, however, this frequency may vary between 150 Hz and 500 Hz. Thus, in the embodiment shown in
In addition, the mixers 541, 542 corresponding to the adders 540b in
In addition, in contrast to the illustrations at
The implementation for the right channel corresponds thereto, wherein the controllable amplifier 1030 whose output signal may be attenuated by means of the attenuator 376 and whose output signal may be mixed with a certain proportion of the common mode signal adjustable by means of the corresponding attenuator is here also provided.
In addition, the low-pass filter 656 as shown in
In contrast to the previous illustrations, e.g. in
In addition, the high-pass member 557 and the low-pass member 535 are provided to accordingly process the raw signal already amplified by the amplifier 1030, i.e. to spectrally filter the same, so as to obtain the low-pass signal from which the base differential mode signal is calculated, and to obtain a high-pass signal that may be mixed to the corresponding tweeter signal, i.e. the high-pass content of the left, or right, channel signal, after a corresponding adjustable attenuation 558. Thus, the high-pass 556, the attenuation member 558, the high-pass 557, the adder 552, and the corresponding attenuation member 551 are used for the actual tweeter signal generation. If, in
Alternatively, a level difference between the tweeter control signal and the entire level of the common mode and the differential mode may also be balanced by means of accordingly amplifying the tweeter signal, or accordingly attenuating both the common mode signal and the differential mode signal for the corresponding sound transducer. In any case, it is advantageous for the amplitudes to be balanced, even though there is no differential mode in the treble range, but there is a corresponding differential mode in the midrange or base range. In embodiments, the midrange speaker or woofer may be configured as a combined transducer that covers both the midrange and the base range. Alternatively, two different transducers may be provided for the midrange and the base range to the extent that the corresponding control signal is of a broadband nature, and then runs over crossover before it reaches the corresponding loudspeakers.
The controllable amplifier 1030 is configured to amplify or attenuate the differential mode signal 1011, i.e. with an adjustable amplification or attenuation according to an adjustment value 1035 that the controllable receiver 1030 receives from the controller 1020. In particular, the apparatus in
The controller 1020 is configured to determine the adjustment value 1035 such that a first adjustment value is determined in case of a first similarity between the first channel signal and the second channel signal, and such that a second adjustment value is determined in case of a second similarity between the first channel signal and second channel signal, wherein the first similarity particularly represents a lower similarity than the second similarity, and wherein the first adjustment value represents a smaller amplification than the second adjustment value or a larger attenuation than the second adjustment value. This connection is schematically illustrated in the mapping function 1000, representing an adjustment value for an amplification (adjustment value larger than 1) and/or for an attenuation (adjustment value smaller than 1), i.e. depending on a similarity scale. In particular, the amplification becomes larger and larger for larger similarity values, i.e. for greater similarities between the first channel signal and second channel signal. This is advantageous to the extent that the level loss of the differential mode signal advantageously generated as a differential signal or an approximate differential signal is balanced, or partially compensated through this. On the other hand, the amplification becomes smaller and smaller the more dissimilar the two channels signals are, since the level of the differential signal decreases and decreases. In particular, a special situation arise if the first channel signal and the second channel signal are particularly dissimilar, i.e. fully correlated, but inversely phased. Then, the calculation of the differential mode signal leads to an superelevation of the level of the differential mode signal, which, according to the mapping function to map similarity values to adjustment values, as schematically illustrated at 1000 in
An amplification may be an amplification that leads to an increase of the level, i.e. an amplification with an amplification factor of larger than 1, or a positive amplification factor on a dB scale. However, an amplification may also be an amplification with an amplification factor of less than 1, i.e. an attenuation. Then, the amplification factor is between 0.1, or within the negative range on a dB scale.
Depending on the embodiment, a direct analysis of the signals to obtain the adjustment value takes place in the apparatus of
Advantageously, the controller 1020 is configured to determine a correlation value between the first channel signal 1001, 71, 306 and second channel signal 1002, 308, wherein the correlation value is a measurement for the similarity. Particularly advantageously, the controller 1020 is configured to calculate a normalized cross-correlation function from the first channel signal and second channel signal, wherein the value of the normalized cross-correlation function is a measurement for the similarity. In particular, the controller 1020 is configured to calculate a correlation value by using a correlation function that has a value range of negative or positive values, wherein the controller is configured to determine for a negative value of the correlation function an adjustment value that represents an attenuation or amplification, and to determine for a positive value of the correlation function the adjustment value that represents an amplification, or attenuation, i.e. the other one. A typical normalized cross-correlation function has a value range of between −1 and +1, wherein the value of −1 signifies that the two signals are fully correlated but reverse in phase, and are therefore, as dissimilar as possible.
On the other hand, a value of +1 is obtained if the two channel signals are fully correlated and of the same phase, i.e. are as similar as possible. The differential mode signal becomes larger and larger with a decreasing value of −1 to 0 in case of a normalized cross-correlation function, which is why the amplification factor in this range is decreased further and further. In case of a value of the normalized cross-correlation function being between 0 and −1, the similarity becomes less and less, which is why the differential mode signal is attenuated more and more, or is amplified less and less, so as to counteract the superelevation of the differential mode signal. Thus, a similarity between the channel signals is synchronized with the cross-correlation function only if the two channel signals are of the same phase, i.e. if the sign of the cross-correlation function is +1. On the other hand, the similarity runs counter to the value of the cross-correlation function if the sign of the cross-correlation function is negative.
A advantageous embodiment of the present invention is located within a mobile device, such as a mobile telephone, a tablet, a notebook, etc. In particular, the control apparatus, or the apparatus for generating a control signal, is loaded as a hardware element or as an app, or a program, on the mobile telephone, the mobile telephone is configured to be able to receive from any source, which may be local or in the internet, the first audio signal, the second audio signal or the multi-channel signal and to generate depending thereon the control signals. These signals are transferred from the mobile telephone to the sound transducer with the sound transducer elements either by means of a cable or a wireless, e.g. by means of Bluetooth or Wi-Fi. In the latter case, it is required that the sound generator elements comprise a battery supply, or a power supply in general, to achieve corresponding amplification of the wireless signals received, e.g. according to the Bluetooth format or according to the Wi-Fi format.
An apparatus for generating control signals for a sound generator therefore includes the differential mode signal generator for generating a differential mode signal from a first channel signal and a second channel signal of a multi-channel audio signal, and a common mode signal generator for generating a first common mode signal from the first channel signal and a second common mode signal from a second channel signal, wherein the apparatus is configured to generate one or several control signals for one or several midrange or bass transducers of the sound generator by using the first common mode signal and the second common mode signal and by using the differential mode signal, and wherein the apparatus is configured to generate a further control signal for a tweeter of the sound generator by using the first common mode signal or the second common mode signal and by using the differential mode signal, or wherein the apparatus is configured to use, when generating the control signals in a bass range, band-selective processing, to use, when generating the control signals in a midrange, the differential mode signal and the common mode signal for controlling one or several midrange or bass transducers of the sound generator (e.g. without band-selective processing), and to control a single tweeter of the sound generator with a combination of the common mode signal and the differential mode signal.
A sound generator includes one or two transducers for a bass range or a midrange, and a tweeter, wherein, e.g., the one or two transducers are arranged to be deflected in a plane perpendicular to a base, and wherein, e.g., the tweeter is configured to be deflected perpendicularly to a base, or wherein, e.g., the one or the two transducers are arranged to be deflected in a plane perpendicular to a surface normal of a front side of the sound generator, and wherein the tweeter is configured to be deflected perpendicularly to the deflection of the two transducers.
A loudspeaker configuration for an instrument panel or a rear shelf in a vehicle includes an above-mentioned sound generator at a left position, an above-mentioned sound generator at a center position, and an above-mentioned sound generator at a right position, or a sound generator with a transducer at a left position, an above-mentioned sound generator at a center position, and a sound generator with a transducer at a right position, or an above-mentioned sound generator at a left position and an above-mentioned sound generator at a right position, or an above-mentioned sound generator at a left position, a sound generator with a transducer at a center position, and an above-mentioned sound generator at a right position.
In a further embodiment of the present invention, when a multi-signal is available, e.g. as a stereo signal or as a signal with three or more channels, the control signals are derived from this multi-channel representation. In case of a stereo signal, e.g., a side signal representing the difference of the left and the right channel is calculated, this side signal then possibly being attenuated or amplified accordingly, and, depending on the implementation, being mixed with a non-high-pass filtered or a high-pass filtered common mode signal. If the output signal has several channels, the mix signals may be generated from differences between any two channels of the multi-channel representation. Thus, e.g., a difference between the left and the right rear (right surround) may be generated, or alternatively, a difference between the center channel and any one of the other four channels of a five-channel representation. In case of such a five-channel representation, however, as is the case in a stereo representation, a difference between left and right may be determined to generate the side signal. In a further embodiment, certain channels of the five-channel representation may be added, i.e. a two-channel down mix may be determined. An exemplary implementation for generating a two-channel down mix signal consists of adding, possibly with weighting factors, left rear (left surround), left, and center, to generate a left down mix channel. To generate the right down mix channel, the right rear channel (right surround) is added with the right channel and the center channel, possibly again with weighting factors. The mix signal may then be determined on the basis of a difference formation from the left down mix channel and the right down mix channel.
Subsequently, advantageous embodiments of the present invention are listed:
Even though some aspects have been described within the context of a device, it is understood that said aspects also represent a description of the corresponding method, so that a block or a structural component of a device is also to be understood as a corresponding method step or as a feature of a method step. By analogy therewith, aspects that have been described within the context of or as a method step also represent a description of a corresponding block or detail or feature of a corresponding device. Some or all of the method steps may be performed while using a hardware device, such as a microprocessor, a programmable computer or an electronic circuit. In some embodiments, some or several of the most important method steps may be performed by such a device.
Depending on specific implementation requirements, embodiments of the invention may be implemented in hardware or in software. Implementation may be effected while using a digital storage medium, for example a floppy disc, a DVD, a Blu-ray disc, a CD, a ROM, a PROM, an EPROM, an EEPROM or a FLASH memory, a hard disc or any other magnetic or optical memory which has electronically readable control signals stored thereon which may cooperate, or cooperate, with a programmable computer system such that the respective method is performed. This is why the digital storage medium may be computer-readable. Some embodiments in accordance with the invention thus comprise a data carrier which comprises electronically readable control signals that are capable of cooperating with a programmable computer system such that any of the methods described herein is performed. Generally, embodiments of the present invention may be implemented as a computer program product having a program code, the program code being effective to perform any of the methods when the computer program product runs on a computer. The program code may also be stored on a machine-readable carrier, for example. Other embodiments include the computer program for performing any of the methods described herein, said computer program being stored on a machine-readable carrier. In other words, an embodiment of the inventive method thus is a computer program which has a program code for performing any of the methods described herein, when the computer program runs on a computer. A further embodiment of the inventive methods thus is a data carrier (or a digital storage medium or a computer-readable medium) on which the computer program for performing any of the methods described herein is recorded. The data carrier, the digital storage medium, or the recorded medium are typically tangible, or non-volatile. A further embodiment of the inventive method thus is a data stream or a sequence of signals representing the computer program for performing any of the methods described herein. The data stream or the sequence of signals may be configured, for example, to be transmitted via a data communication link, for example via the internet. A further embodiment includes a processing unit, for example a computer or a programmable logic device, configured or adapted to perform any of the methods described herein. A further embodiment includes a computer on which the computer program for performing any of the methods described herein is installed.
A further embodiment in accordance with the invention includes a device or a system configured to transmit a computer program for performing at least one of the methods described herein to a receiver. The transmission may be electronic or optical, for example. The receiver may be a computer, a mobile device, a memory device or a similar device, for example. The device or the system may include a file server for transmitting the computer program to the receiver, for example. In some embodiments, a programmable logic device (for example a field-programmable gate array, an FPGA) may be used for performing some or all of the functionalities of the methods described herein. In some embodiments, a field-programmable gate array may cooperate with a microprocessor to perform any of the methods described herein. Generally, the methods are performed, in some embodiments, by any hardware device. Said hardware device may be any universally applicable hardware such as a computer processor (CPU), or may be a hardware specific to the method, such as an ASIC.
While this invention has been described in terms of several embodiments, there are alterations, permutations, and equivalents which fall within the scope of this invention. It should also be noted that there are many alternative ways of implementing the methods and compositions of the present invention. It is therefore intended that the following appended claims be interpreted as including all such alterations, permutations and equivalents as fall within the true spirit and scope of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2021 211 051.7 | Sep 2021 | DE | national |
| 22173339.7 | May 2022 | EP | regional |
This application is a continuation of copending International Application No. PCT/EP2022/077207, filed Sep. 29, 2022, which is incorporated herein by reference in its entirety, and additionally claims priority from German Application No. DE 10 2021 211 051.7, filed Sep. 30, 2021, and European Application EP 22 173 339.7, filed May 13, 2022, all of which are incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/EP2022/077207 | Sep 2022 | WO |
| Child | 18615161 | US |
