The present application relates to the field of sound generation, and particularly to an apparatus and a method for enhancing a spatial perception of a two-channel audio signal.
There are many devices with two transducers on the market, such as laptops, tablet computer, mobile phones, and smartphones, as well as portable media players or smartphone docking stations and soundbars for TVs. Compared to a conventional stereo system with two discrete loudspeakers, the two transducers of such devices are located in a single cabinet or enclosure and are typically placed very close to each other. Due to the size of these devices, the transducers are usually spaced from each other by only few centimeters.
This results in a narrow sound reproduction, almost “mono-like”. When playing a stereo recording on such devices, all sound sources are perceived as being centered.
Several different solutions have been proposed in order to increase the spatial effect of such systems with small loudspeaker span angles using different concepts.
EP 2 222 092 B1, for example, describes beamforming used in soundbars, with the goal to reflect acoustic beams of sound on walls surrounding the listener in order to achieve a spatial effect. The impression of sound arriving from the right side can be achieved by steering a beam to a position on the right wall where it is reflected and arrives at the listener. While this method can achieve convincing spatial effects, it requires a large number of transducers and relies on regular walls with good reflective properties all around the listener. Furthermore, a calibration of the system is needed to adapt to the room properties.
It is the object of the invention to provide an improved technique for reproducing a two-channel audio signal, e.g. a stereo signal or a binaural signal.
This object is achieved by the features of the independent claims. Further implementation forms are apparent from the dependent claims, the description and the figures.
According to a first aspect, an apparatus for enhancing a spatial perception of a two-channel audio signal is provided, the two-channel audio signal comprising a first audio channel signal and a second audio channel signal, wherein the apparatus comprises a dipole steering unit, and wherein the dipole steering unit comprises: a first dipole steering module adapted to produce a first dipole signal based on the first audio channel signal, a second dipole steering module adapted to produce a second dipole signal based on the second audio channel signal; wherein the first dipole steering module and the second dipole steering module are adapted to produce the first dipole signal and the second dipole signal such that, when output via a transducer unit, a first zero sound propagation direction of the first dipole signal has a positive azimuth angle with regard to a steering reference direction, and a second zero sound propagation direction of the second dipole signal has a negative azimuth angle with regard to the steering reference direction, and wherein transducer unit comprises at least one pair of transducers. The apparatus can comprise the transducer unit, e.g., can comprise an integrated transducer unit, or can be connected or at least connectable to a separate transducer unit.
The invention is based on the finding that a spatial effect can be obtained by creating increased interaural-level differences. Interaural-level differences refer to differences in sound pressure level between the two ears of a listener. To obtain this effect, two dipoles are used: one for producing a left side signal and one for producing a right side signal.
The left side dipole is rotated by αL>0°, the right side dipole is rotated by αR<0°. As a result, the right side dipole emits more energy to the right side; the left side dipole emits more energy to the left side. In comparison to rendering left and right side signals with omni-directional characteristic, the interaural-level differences are increased. The increased interaural-level differences between left and right ear create a stereo widening effect: the width of the stereo image is increased and sources may be localized outside of the line segment between the two loudspeakers and at a larger angle than the loudspeaker span angle.
The apparatus allows increased spatial effects for small loudspeaker span-angles, e.g., for mobile devices. The spatial effect is based on increased interaural-level differences, computation and implementation are simple, the apparatus does not require many transducers, it can even be used with just two transducers. Advantageously, the apparatus can be easily adapted to different setups, with various numbers of transducers and different spacing.
The apparatus is robust and not affected by ill-conditioned filter inversion as conventional crosstalk cancellation. No colorization occurs in the sweet spot, and only little colorization is present outside of the sweet spot. The stereo widening effect even occurs outside of the sweet spot and interaural level differences can be adjusted using the steering angle.
The invention can be employed for widening stereo playback using the crosstalk cancellation embodiment in combination with a head-related transfer function (HRTF) which is a response that characterizes how an ear receives a sound from a point in space. It is also possible to place sources all around the listener to achieve virtual surround sound.
In a first possible implementation form of the apparatus according to the first aspect, the first dipole signal and the second dipole signal are further produced such that, when output via the transducer unit, a first main sound propagation direction of the first dipole signal has a negative azimuth angle with regard to the steering reference direction, and a second main sound propagation direction of the second dipole signal has a positive azimuth angle with regard to the steering reference direction.
The usage of two differing main sound propagation directions for each of the dipole signals beneficially permits to increase the spatial effect for small loudspeaker span angles as, for instance, available in mobile devices.
In a second possible implementation form of the apparatus according to the first aspect as such or according to the first implementation form of the first aspect, the first audio channel signal is a left audio channel signal, the second audio channel signal is a right audio channel signal, and the first dipole signal and the second dipole signal are further produced such that, when the steering reference direction points towards a user facing the transducer unit, the first zero propagation direction points towards the right ear of the user, and the second propagation direction points towards the left ear of the user.
The apparatus allows providing dipole signals with enhanced spatial perception steering to a desired direction, e.g. to a direction, to which a listener is and in particular the ears of the listener are positioned and, thus, provides an improved technique for reproducing or generating a stereo signal. Interaural-level differences can be adjusted to the desired perceivable level using the steering angle.
In a third possible implementation form of the apparatus according to the first aspect as such or according to the any of the preceding implementation forms of the first aspect, the transducer unit comprises a first pair of transducers and a second pair of transducers, wherein the first pair of transducers is configured to emit the first dipole signal and the second pair of transducers is configured to emit the second dipole signal, wherein the first pair of transducers and the second pair of transducers are located in fixed position with respect to each other. The two pairs of transducers may, for example, be integrated in a housing of a device.
The apparatus comprising two pairs of transducers is more robust and not affected by ill-conditioned filter inversions as conventional crosstalk cancellation.
In a fourth possible implementation form of the apparatus according to the third implementation form of the first aspect, the first pair of transducers and the second pair of transducers are spaced by a distance of less than 5 cm, less than 10 cm, or less than 40 cm.
When the distance is within that range, the enhanced spatial effect can be steered in all possible directions in front of a mobile device or a docking station or a soundbar applying that method.
In a fifth possible implementation form of the apparatus according to the first aspect as such or according to any of the preceding implementation forms of the first aspect, the first dipole steering module and the second dipole steering module are adapted to produce the first dipole signal and the second dipole signal such that, when output via the transducer unit, perceivable interaural-level differences in a sound field are generated by the transducer unit.
A just noticeable change in interaural-level difference is between 0.5 and 1 dB. A spatial effect may be based on perceivable interaural-level differences of approximately 4 dB level differences or larger.
In comparison to rendering left and right side signals with omni-directional characteristic, the interaural-level differences are increased. The increased interaural-level differences between left and right ear create a stereo widening effect.
In a sixth possible implementation form of the apparatus according to the first aspect as such or according to any of the preceding implementation forms of the first aspect, the apparatus further comprises a filter bank unit adapted to filter the input audio signal with a filter characteristic generating a bandwidth limited input audio signal, which is provided as input signal for the dipole steering unit.
A filter bank unit is an array of band-pass filters that separates the input signal into multiple components.
In a seventh possible implementation form of the apparatus according to the first aspect as such or according to any of the preceding implementation forms of the first aspect, the transducing unit comprises only one pair of transducers, wherein the one pair of transducers is connected such to the dipole steering module that the one pair of transducers is adapted to emit the first dipole signal and the second dipole signal.
This allows a further reduction concerning the number of transducers needed for a sound generation with enhanced a spatial perception.
In an eighth possible implementation form of the apparatus according to the first aspect as such or according to any of the preceding implementation forms of the first aspect, each of the first dipole signal and the second dipole signal contains a first signal component and a second signal component which are different with respect to sign and phase.
The inverted signal component of the first dipole signal and the second dipole signal enables the creation of the non-omni-directional characteristic.
In a ninth possible implementation form of the apparatus according to the eighth implementation form of the first aspect, the dipole steering unit is configured to adapt the first audio channel signal and the second audio channel signal such that the difference in phase between the first signal component and a second signal component is obtained by delaying the first signal component or the second signal component.
The delaying advantageously allows by means of an implementation by integrated electronics to generate a difference in phase between the first signal component and a second signal component and enables the steering of the dipole towards different angles.
In a tenth possible implementation form according to the eighth implementation form of the first aspect or according to the ninth implementation form of the first aspect, the dipole steering unit is configured to adapt the first audio channel signal and the second audio channel signal such that the difference in sign between the first signal component and a second signal component is obtained by inverting the first signal component or the second signal component.
The inverting can be advantageously conducted by means of an implementation of integrated electronics.
In an eleventh implementation form according to any of the preceding implementation forms of the first aspect or according to first aspect, the dipole steering unit further comprises a filter bank unit and a first summation amplifier and a second summation amplifier; wherein the filter bank unit is configured to separate each of the first audio channel signal and the second audio channel signal, into at least a low frequency subband component, a mid frequency subband component and a high frequency subband component; wherein the first dipole steering module is configured to receive and process the mid frequency component of the first audio channel signal; wherein the second dipole steering module is configured to receive and process the mid frequency component of the second audio channel signal; wherein the first summation amplifier is adapted to receive and sum the steered mid frequency component of the first audio channel signal from the first dipole steering module and the low frequency component and the high frequency component of the first audio channel signal from the filter bank unit, and to output the summed signal as a first transducer driving signal; and wherein the second summation amplifier is adapted to receive and sum the steered mid frequency component of the second audio channel signal from the second dipole steering module and the low frequency component and the high frequency component of the first audio channel signal from the filter bank unit, and to output the summed signal as a first transducer driving signal.
According to a second aspect, the invention relates to a mobile device comprising an apparatus according to the first aspect as such or according to any of the preceding implementation forms of the first aspect, wherein the at least one pair of transducers of the transducer unit of the apparatus is provided by at least one pair of loudspeakers of the mobile device.
This provides an increased spatial effect even for small loudspeaker span angles as given in mobile devices.
According to a third aspect, the invention relates to a docking station comprising an apparatus according to the first aspect as such or according to any of the preceding implementation forms of the first aspect, wherein the at least one pair of transducers of the transducer unit of the apparatus is provided by at least one pair of loudspeakers of the docking station.
According to a fourth aspect, the invention relates to a soundbar comprising an apparatus according to the first aspect as such or according to any of the preceding implementation forms of the first aspect, wherein the at least one pair of transducers of the transducer unit of the apparatus is provided by at least one pair of loudspeakers of the soundbar.
According to a fifth aspect, the invention relates to a method for enhancing a spatial perception of a two-channel audio signal, the two-channel audio signal comprising a first audio channel signal and a second audio channel signal, said method comprising the steps of: producing a first dipole signal based on the first audio channel signal and producing a second dipole signal based on the second audio channel signal, wherein the first dipole signal and the second dipole signal are produced such that, when output via a transducer unit comprising at least a pair of transducers, a first zero sound propagation direction of the first dipole signal has a positive azimuth angle with regard to a steering reference direction, and a second zero sound propagation direction of the second dipole signal has a negative azimuth angle with regard to the steering reference direction.
The method can be applied for multichannel audio signals. Thus, the method can be applied for compressed stereo signals. The method can be used for decreasing computational complexity.
In a first possible implementation form of the method according to the fifth aspect, the method further comprises the step of adapting the left side signal and the right side signal by means of the dipole steering unit to generate increased interaural-level differences in a sound field generated by the transducer unit.
Implementing the method saves computational complexity.
The methods, systems and devices described herein may be implemented as software in a Digital Signal Processor (DSP) in a micro-controller or in any other side-processor or as hardware circuit within an application specific integrated circuit (ASIC).
The invention can be implemented in digital electronic circuitry, or in computer hardware, firmware, software, or in combinations thereof, e.g., in available hardware of conventional mobile devices or in new hardware dedicated for processing the methods described herein.
Further embodiments of the invention will be described with respect to the following figures, in which:
The stereo mobile device 200 comprises a left path transducer 120-L and a right path transducer 120-R. The transducers 120-L and 120-R can be comprised in or can be conventional omnidirectional loudspeakers, i.e., no special hardware for implementing dipole loudspeakers is required for embodiments of the invention comprising a dipole steering unit as described later in more detail.
As illustrated in
As illustrated in
In the following embodiments of dipole steering modules and dipole steering units as well as exemplary embodiments of dipole processing circuits implemented therein are described.
In the circuit as shown in
The corresponding directional dipole response of the circuit as shown in
The dipole steering module 110 comprises a multiplication amplifier module 113 and a delaying module 114.
The dipole characteristic is achieved using the two spaced transducers 120-L, 120-R which are spaced by a distance d. A signal s (t) from an input of the dipole steering module 110 is directly given as signal x1(t) at a plus-phased (+) output of the dipole steering module 110 to the first transducer or loudspeaker 120-L, and a corresponding inverted and delayed signal x2(t) at a minus-phased (−) output of the dipole steering module 110 is given to the second transducer or loudspeaker 120-R, as illustrated in
By adding the further delay compared to the circuit in
x
1(t)=s(t)
x
2(t)=−s(t−τ). Equation (1)
t denotes the time variable and τ denotes the delay introduced by delaying module 114. The sound field p(r,t) at radius r generated by such a pair of transducers in the far-field is
c denotes to the speed of sound, ω denotes to angular frequency. At low frequencies, equation (2) can be approximated by
from which it can be seen that the ratio
corresponds to a parameter, determining the directional response
directivity(φ)=u+(1−u) cos φ. Equation (4)
d represents the distance between the transducers. In a preferred embodiment, this distance is rather small and compatible with mobile device applications. It is then in the range of 2 to 40 cm. The parameter u, which steers the null towards αε[0, . . . , π/2] is
For negative αε[0, . . . , −π/2], the delay and inversion are applied to the other transducer and u in equation (5) is computed for |α|. The delay τ, corresponding to this u is
In the first polar radiation plot (top left of
In the second polar radiation plot (top right of
In the third polar radiation plot (bottom left of
In the fourth polar radiation plot (bottom right of
In the following, technical principles of embodiments of the invention will be explained based on
Therefore, as will be described in more detail starting from
Accordingly, the first dipole signal and the second dipole signal are produced by the corresponding dipole steering modules such that, when output via the transducer unit, a first zero sound propagation direction ZDL of the first dipole signal has a positive azimuth angle with regard to a steering reference direction SRD, and a second zero sound propagation direction ZDR of the second dipole signal has a negative azimuth angle with regard to the steering reference direction SRD. The steering reference direction SRD is, as shown in
According to further embodiments of the invention, the dipole steering can be also configured to obtain a crosstalk cancellation effect. In such embodiments the zero sound propagation direction of the dipole signals is steered to face the contra-lateral ear, as shown in
In other words, such embodiments maximize the inter-aural level differences: the level is maximized at the ipsi-lateral ear and minimized at the contra-lateral ear. This concept gives a similar crosstalk cancellation effect as filter inversion techniques but uses simpler and more robust dipole processing techniques.
The optimal steering or rotation angles αR, αL for the crosstalk cancellation embodiment depend on the listening distance L, i.e., the distance between the listener 190 and the device 200 respectively the transducer unit comprising the transducers, and the ear distance E, i.e., the distance E between the left ear LE and the right ear RE of the listener, see
and the delay is obtained using equations (5) and (6). Hence, it can be seen that a first or left zero sound propagation direction ZDL of the first or left dipole signal has a positive azimuth angle (e.g. αL) with regard to a steering reference direction SRD, and a second or right zero sound propagation direction ZDR of the second or right dipole signal has a negative azimuth angle (e.g. αR) with regard to the steering reference direction.
Typical values (magnitudes) for a (e.g. αR and/or αL) for different scenarios are approximately:
The transducer unit 120 comprises the first transducer 120-L and the second transducer 120-R. The dipole steering module 110 comprises the multiplication amplifier module 113, which may also be designated as separation and inverting module 113, and the delaying module 114.
The implementation form of the dipole steering module 110 shown in
The equalization filter module 150 may be designed or configured to compensate for the low-frequency gain loss of the dipole, when output via the transducers.
In embodiments of the dipole steering module 110 as shown in
Exemplary filter magnitude responses are shown in
Alternative embodiments of the dipole steering module 110 as described based on
In the embodiments described in the following, exemplarily the implementation form of the dipole steering module 110 shown in
The dipole steering unit 1102 comprises two dipole steering modules, each dedicated to one dipole signal, i.e., a first or left dipole steering module 110-L adapted to steer the first or left dipole signal DSL and a second dipole steering module 110-R adapted to steer the second or right dipole signal DSR. The dipole steering unit can also be referred to as stereo reproduction unit. The transducer unit 120 comprises four transducers 120-L1, 120-L2, 120-R1 and 120-R2, which are used to form two pairs of dedicated transducers, one pair for each dipole signal, i.e. the transducers 120-L1, 120-L2 form the first or left transducer pair for the first or left dipole signal DSL and the transducers 120-R1, 120-R2 form the second or right transducer pair for the second or right dipole signal DSR.
To summarize, the embodiment shown in
The first (e.g., left channel) dipole steering module 110-L is adapted to produce a first dipole signal DSL (e.g., left dipole signal DSL) based on the first audio channel signal ASL.
The second (e.g., right channel) dipole steering module 110-R is adapted to produce a second dipole signal DSR (e.g., a right dipole signal DSR) based on the second audio channel signal ASR.
The first dipole signal DSL (e.g. xL1(t) and xL2(t)) and the second dipole signal DSR (e.g. xR1 (t) and xR2(t)) are produced by the dipole steering modules 110-L, 110-R such that, when output via the transducer unit 120, a first zero sound propagation direction ZDL of the first dipole signal DSL has a positive azimuth angle with regard to a steering reference direction SRD, and a second zero sound propagation direction ZDR of the second dipole signal DSR has a negative azimuth angle with regard to the steering reference direction.
In embodiments of the apparatus 1100, the first and second dipole steering module may be implemented, for example, as described based on
In the following an embodiment of the apparatus 1100 will be described, wherein the first and second dipole steering modules 120-L and 120-R are implemented as described based on
Accordingly, the first dipole steering module 110-L comprises an equalization filter module 150, an inverting module 113 and a delaying module 114. The first dipole steering module 110-L is adapted to output at the positive phase output (see “+” of 110-L in
The second dipole steering module 110-R also comprises an equalization filter module 150, an inverting module 113 and a delaying module 114. The second dipole steering module 110-R is adapted to output at the positive phase output (see “+” of 110-R in
According to a further embodiment, it is possible to combine two dipole steering modules 110-L, 110-R to implement a dipole steering unit 1202 which only requires one pair of transducers 120-L and 120-R. In such embodiments the two transducers 120-L and 120-R of the transducer unit 120 are shared between the two dipole steering modules 110-L and 110-R as shown in
To achieve this sharing of the two transducers, the apparatus 1200 comprises a dipole steering unit 1202, which differs from the dipole steering unit 1102 shown in
In the following an embodiment of the apparatus 1200 will be described, wherein the first and second dipole steering modules 110-L and 110-R are implemented as described based on
As shown in
Furthermore a minus-phased output of the first dipole steering module 110-L, at which a filtered, delayed and inversed version xL2(t) of the first audio channel signal sL(t) is provided, is connected to a first input of the second summation amplifier 116. A plus-phased output of the second dipole steering module 110-2, at which a filtered version xR2(t) of the second audio channel signal sR(t) is provided, is connected to a second input of the second summation amplifier 116. An output of the second summation amplifier 116, at which the combined or sum signal of the two aforementioned signals is provided as driving signal DR for the second transducer 120-R, is connected to a second transducer 120-1 of the transducer unit 120. Hence, the resulting circuit is a cross-connection circuit.
The number of required transducers 120-1 is therefore minimized, in the given circuit from four to two transducers when compared to the circuit of
Two loudspeakers of the device 1300 are used as the two transducers 120-L and 120-R or comprise the two transducers 120-L and 120-R.
The directional response of the dipole depends on the loudspeaker distance d between the two transducers 120-L and 120-R and the frequency f of the audio signal output by the transducers. As a result, the dipole steering is effective in a limited frequency range. Towards high frequencies, the characteristic shape of the response diminishes. Towards low frequencies, the dipole response receives a 6 dB roll-off per octave which would require a large equalization gain, in particular in mobile devices with a small loudspeaker distance d.
Therefore, the apparatus 1300 comprises a dipole steering unit 1302 which comprises additionally to the components of the dipole steering unit 1202 a filter bank unit 1304 (see
The transition frequencies depend on the distance d and angle α as well as the acceptable equalization gain. For the example shown in
The apparatus 1400 differs from the apparatus 1300 in that it comprises four transducers 120-1, 120-2, 120-3, 120-4 instead of only two transducers 120-L and 120-R. Furthermore, each filter bank element 130-L, 130-R of a dipole steering unit 1402 of the apparatus is configured to separate its received audio channel signal sL(t), sR(t) into 4 subbands: low frequencies (referenced as “low” in
From
In the dipole steering unit 1402, a first summation amplifier 115a receives the high and low frequencies of the first audio channel signal sL(t), the filtered version of the lower mid frequencies of the first audio channel signal sL(t) from a first dipole steering unit 110-1, and the filtered, delayed and inversed version of the lower mid frequencies of the second audio channel signal sR(t) from a second dipole steering unit 110-2. An output of the first summation amplifier 115a is connected to the first transducer 120-1.
Furthermore, a second summation amplifier 116a receives the high and low frequencies of the second audio channel signal sR(t), the filtered version of the lower mid frequencies of the second audio channel signal sR(t) from the second dipole steering unit 110-2, and the filtered, delayed and inversed version of the lower mid frequencies of the first audio channel signal sL(t) from the first dipole steering unit 110-1. An output of the second summation amplifier 116a is connected to the second transducer 120-2.
Furthermore a third summation amplifier 115b receives the filtered version of the higher mid frequencies of the first audio channel signal sL(t) from a third dipole steering unit 110-3, and the filtered, delayed and inversed version of the higher mid frequencies of the second audio channel signal sR(t) from a fourth dipole steering unit 110-4. An output of the third summation amplifier 110-3 is connected to the third transducer 120-3.
Finally a fourth summation amplifier 116b receives the filtered version of the higher mid frequencies of the second audio channel signal sR(t) from the fourth dipole steering unit 110-4, and the filtered, delayed and inversed version of the higher mid frequencies of the first audio channel signal sL(t) from the third dipole steering unit 110-3. An output of the fourth summation amplifier 110-4 is connected to the fourth transducer 120-4.
Based on the circuit shown in
According to the embodiment shown in
To summarize,
By using the two pairs of transducers 120-1, 120-2, 120-3, 120-4, with differing distance d and two different subbands for the dipole steering, the effective frequency range of the enhanced spatial effect can be increased. The different distance d requires a different delay τ according to Eqn. 6. Also the equalization filter 150 is adapted according to the differing distance d.
As described, low and high frequencies are directly provided to the transducers 120-1, 120-2 (denoted 1 and 2). The lower mid frequencies are provided to the low frequency dipole 1 (d=0.2 m), the higher mid frequencies are provided to the high frequency dipole 2 (d=0.1 m). For such embodiments, the transition frequency between the two dipoles (Dipoles 1 and 2 in
Thus, contrary to
When compared to the apparatus 1400 (transducer arrangement as shown in
In the apparatus shown in part in
The connection of each of the four transducers 120-1, 120-2, 120-3, 120-4 as illustrated in
Each of
A stereo signal s(t) comprising a left audio channel signal sL(t) and a right audio channel signal sR(t) is provided to an input of a dipole steering unit 1602, for example a dipole steering unit 1202 or 1302 for two transducers 120-L and 120-R as described based on
Processing stereo signals according to embodiments of the invention results in a stereo widening effect which is based on the increased interaural-level differences. Stereo widening refers to the perception of sound sources which are located outside of the loudspeaker span angle Θ (see
As shown in
A stereo signal s(t) comprising a left audio channel signal sL(t) and a right audio channel signal sR(t) is provided to an input of a HRTF processing unit 1740. An output of the HRTF processing unit 140 provides a binaural signal comprising a left binaural signal sBL(t) and a right binaural signal sBR(t) to the dipole steering unit 1702 as first and second audio channel signal. The dipole steering unit 1702 is, for example, a dipole steering unit 1202 or 1302 for two transducers 120-L and 120-R as described based on
As shown in
A multichannel signal is provided to an input of a HRTF processing unit 1840. The multi-channel comprises a plurality N of audio channel signals, typically more than 2, but may also be represented by a downmix signal and corresponding spatial side information. An output of the HRTF processing unit 1840 provides a binaural signal comprising a left binaural signal sBL(t) and a right binaural signal sBR(t) to the dipole steering unit 1802 as first and second audio channel signal. The dipole steering unit 1802 is, for example, a dipole steering unit 1202 or 1302 for two transducers 120-L and 120-R as described based on
The method for enhancing a spatial perception of a two-channel audio signal may comprise the following steps.
Producing S1 a first dipole signal based on the first audio channel signal and producing a second dipole signal based on the second audio channel signal, wherein the first dipole signal and the second dipole signal are produced such that, when output via the transducer unit, a first zero sound propagation direction of the first dipole signal has a positive azimuth angle with regard to a steering reference direction, and a second zero sound propagation direction of the second dipole signal has a negative azimuth angle with regard to the steering reference direction.
Transducing S2 the first dipole signal and the second dipole signal by means of a transducer unit 120.
It should be noted that embodiments of the invention can be implemented not only in or by those devices or methods as described, for example, based on
In embodiments of the invention the delaying modules 114 of the first and second dipole steering units 110-L and 110-R (e.g., in
However, it should be noted that also non-symmetric steering, e.g., by applying different steering angles based on different delays in the delaying modules 114 of the first and second dipole steering units 110-L and 110-R, may provide an enhanced spatial perception (increased ILD or crosstalk cancellation) compared to conventional solutions, although typically the perception improves with increasing symmetry, i.e., the smaller the difference of the magnitudes of the steering angles is.
It should be further noted that alternative embodiments of the apparatus 1100 may comprise alternative implementations to steer the dipole signals and in particular the zero propagation directions of the dipole signals to achieve the same effect. Embodiments may, e.g., not comprise a filtering module 150. Further embodiments may swap the location of the left and right transducer 120-L1 and 120-L2 of the left transducer pair and/or the location of the left and right transducer 120-R1 and 120-R2 of the right transducer pair, or may swap the electrical connections between the positive and negative phase outputs and the corresponding transducers, e.g. connect the left transducer 120-L1 of the left transducer pair with the negative phase output of the left dipole steering module 110-L and to connect the right transducer 120-L2 of the left transducer pair with the positive phase output of the left dipole steering module 110-L.
For ease of understanding, with regard to the description of the various embodiments of the invention angles have been defined to be positive angles in counter-clockwise direction. However, it is to be understood that for embodiments of the invention angles may also be defined to be positive angles in clockwise direction. In the latter case the inverse applies correspondingly.
Furthermore, it should be noted that for ease of understanding, embodiments of the invention have been primarily been described based on stereo signals s (t) as two-channel signal, the stereo signal s(t) comprising a left channel audio signal sL(t) and a right channel audio signal sR (t), wherein the left channel audio signal sL(t) formed the first input signal ASL and the right channel audio signal sR(t) formed the second input signal ASR. However, embodiments of the invention are also adapted to use other audio signals as two-channel signal, e.g., binaural signals or any other two audio channels, e.g., each captured by a dedicated microphone or one or both audio channel signals synthetically generated, to providing an enhanced spatial perception of the two audio channel signals.
From the foregoing, it will be apparent to those skilled in the art that a variety of methods, systems, computer programs on recording media, and the like, are provided.
The present disclosure also supports a computer program product including computer executable code or computer executable instructions that, when executed, causes at least one computer to execute the performing and computing steps described herein.
Many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the above teachings. Of course, those skilled in the art readily recognize that there are numerous applications of the invention beyond those described herein.
While the present invention has been described with reference to one or more particular embodiments, those skilled in the art recognize that many changes may be made thereto without departing from the scope of the present invention. It is therefore to be understood that within the scope of the appended claims and their equivalents, the inventions may be practiced otherwise than as specifically described herein.
In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims.
The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage. A computer program may be stored or distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems.
This application is a continuation of International Application No. PCT/EP2013/075975, filed on Dec. 9, 2013, which is hereby incorporated by reference in its entirety.
Number | Date | Country | |
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Parent | PCT/EP2013/075975 | Dec 2013 | US |
Child | 15177994 | US |