Patent Application
20130101134
This substitute specification, in a single file as both a marked up and clean version herein, having no changes except formatting, contains no new matter, per 37 CFR 1.125(b).
This invention relates to the use of wireless microphones for stage performances where the position of the performer is used to create stereo audio outputs whose audio signals provide audio information to listeners as to the position of the performer.
Wireless microphones are commonly used by stage performers, including singers, musicians, actors, hosts, moderators, and speakers. A key advantage of wireless microphones is the lack of a microphone cord, thus enabling the performer to easily move around the stage, or even into the audience or other areas, including off-stage or even outside of the performance area.
Most wireless microphones are monophonic, or mono, meaning they pickup and transmit a single audio channel.
There are stereo microphones, designed primarily for used in fixed positions to pickup sounds from two more or less independent directions, usually from more than one sound source, such as a group of performers. Such stereo microphones may be used, with audio signals routed through amplifiers to stereo speakers, such that the apparent position of the performers to the audience approximately matches the actual physical position of the performers on the stage.
This apparent audio position, as perceived by the listening audience, when it matches the visual or actual position of the performers, provides a more consistent and more enjoyable listening experience. This apparent audio position of the sound source to a listener is sometimes called stereo imaging.
The use of mono wireless microphones generally prevents the presentation to a listener of an apparent matching audio position of the performer. The volume of the performer's audio signal is either set to be equal on the left and right speakers, thus creating an apparent audio position of the performer at the center of the stage, or the relative amplitudes of the signals going to the left and right speakers is unequal, as set by the sound designer or sound person for the production, creating an apparent but fixed audio position of the performer left or right of stage center. In these cases, there is no automatic means to adjust the apparent audio position of the performer as the performer moves around the stage, or moves off the stage during a performance.
This invention overcomes the specific weakness of mono wireless microphones not providing apparent audio position of the performer to match the actual position of the performer on the stage.
This invention, in one embodiment, uses traditional mono wireless microphone components, including a monaural sensor and monaural wireless transmitting channel. Two additional components are including in the invention to create an automatic means of providing apparent matching audio position of the performer. The first additional component is a position locating means that locates the position of the performer on the stage. This position locating means may locate either the performer or the microphone, although in most cases the performer and the microphone are proximal. The second additional element is a module that accepts the monaural signal from the wireless microphone and the position information as input, and then provides two or more channels of audio output to go via amplifiers to at least a left and right speaker. We refer to this module as a splitter.
In a stereo embodiment, the splitter would generally provide equal amplitude signals to the left and right channels to match a stage-center physical position of the performer. The splitter would provide a signal at 100% amplitude to the left channel and 0% amplitude to the right channel to match a far stage-left position, with a symmetric output to match a far stage-right position. Intermediate amplitudes for the left and right channel outputs are used to create matching intermediate positions of the performer for intermediate positions between stage center and stage-left or stage center and stage-right. Typically, the relative amplitude of the left and right signals is proportional to the left-right stage position of the performer, however this proportionality does not have to be linear.
There are many methods of locating a performer described in the prior art. Such methods include tracking via audio signals, tracking via light sources at the performer, tracking via radio wave emission at the performer, sonic reflection, vision recognition systems, physical sensors, and other methods. Other possible systems include the use of a GPS receiver at the performer's position, RFID tags, or using the output from a follow spot. For example, one such system could use a GPS receiver coupled with a Bluetooth transmitter. This combination exists in common, low-cost personal electronic devices that have the ability to run applications suitable for this purpose. For this invention we do not recommend any particular position locating system. Indeed, appropriate location positions systems are likely to depend both on the needs of the application and available technology.
We do describe one such position detection system that has the advantage of using already existing components of a typical wireless microphone.
In this embodiment of a position locating system the amplitude of the wireless audio signal, as broadcast by the wireless microphone is used to detect position. In a first embodiment, a single receiver may be used, where the amplitude of the received signal amplitude decreases with the distance of the microphone from the receiver. In a second and preferred embodiment two receivers are used, each located approximately stage left and stage right, and the relative amplitudes of the received signal are used to determined position, again using the fact that the signal amplitude decreases with the distance of the microphone from the receiver.
The first embodiment described above for the position detection has the unique advantage that it requires no change at all to existing wireless microphones and can be incorporated very inexpensively into the wireless receiver. Thus the same number of components with the same names and primarily the same functions as the components currently commonly in use as wireless microphone systems are used to implement this system. This feature provides for ease of deployment and rapid customer acceptance due the very small change in understanding and deployment.
The second embodiment described above for the position detection has the unique advantage of that it requires no change at all to existing wireless microphones and can be incorporated very inexpensively into a current wireless receiver design, although two receivers would be deployed in the performance arena in place of the current single receiver. Two receivers have the additional advantage that in the case of receiver failure audio is not completely lost resulting in minimum disruption of the performance in progress.
In either the first or second embodiment described above for the position detection existing circuitry in the receiver may be used to provide part of the functionally of this invention. In particular, most receivers have a circuit component called an automatic gain control, or AGC. Typically the amplitude of the radio frequency signal at the receiver varies significantly. An AGC includes a variable gain amplifier that provides a more uniform amplitude signal out even under wide variations of the amplitude of the signal in. The variable gain amplifier typically has a control input signal that indicates the desired gain of the amplifier, usually with a logarithmic relationship between the amplitude of the control signal, usually a voltage, and the gain of the amplifier.
In one embodiment of the position detection circuit the above-described existing AGC control signal is used to provide information about the amplitude of the incoming radio signal from the wireless microphone and thus the position of the performer as a distance from the receiver. Typically, some non-linear correction is needed to convert the amplitude of this control signal to a signal that linearly represents the position of the performer on the stage. Such correction may be provided with an analog circuit or with digital computation. Such non-linear correlation may not be required in all embodiments, as this AGC control signal may already be an acceptable approximate linear representation of the performer's stage position.
In an embodiment where two or more receivers are used, the receivers need to communicate by some means so that the modulator or modulators have as input the best available position information of the performer as determined by the combined information from the plurality of receivers. In the simplest embodiment, the ratio of the amplitudes of the two AGC control signals in the two receivers determines the position of the performer on the stage. Some non-linear correction may be needed for this ratio.
In a preferred embodiment, this invention includes two controls in order to improve the accuracy of the apparent audio position of the performer relative to the physical location of the performer on the stage. The first control is called, “gain.” This control sets the multiplier from the received position information to the ratio of left-right outputs of the modulator. A higher gain setting moves the amount of the left or right apparent position farther for a smaller physical shift from stage center. A lower gain setting similarly move the amount of left or right apparent position smaller for a larger physical position change of the performer. A gain setting of zero would place the apparent audio position of the performer at stage center no matter where the performer was actually located. A second desirable control is called, “offset.” This control changes the apparent audio position of the performer left or right of the performer's actual position. This control is particularly useful if the two receivers, for a two-receiver embodiment, are not located symmetrically at the sides of the stage. Ideally,
The combination of the gain and offset controls is typically used in order to accurately recreate an apparent audio position of the performer that consistently corresponds to the performer's actual position on the stage.
In an ideal embodiment there are one, two, or three, “calibration buttons.” In a single calibration button embodiment, one button is used to indicate that the performer is in a preset location. In one embodiment the button is used to indicate that the performer is now at stage center. This button then sets the equal-output point of the modulator, for a stereo embodiment of the modulator. In a two-button embodiment one button sets the “stage-left” position and the second button sets the “stage-right” position of the performer. In the three calibration button embodiment, one button sets stage center, a second button sets stage left, and a third button sets the stage right position.
The use of calibration buttons in the embodiment may provide easier setup and may provide more accurate apparent audio positioning. The use of calibration buttons in the embodiment may eliminate the need or use of manual gain and offset controls, although such manual controls may still be desirable.
The calibration buttons may be located on one or more receivers. Such an embodiment provides the fewest physical components in the complete system. Calibration buttons located on the left and right receivers, in a stereo embodiment, allow the performer himself or herself, typically, to perform a two-button calibration without the assistance of a second person.
In yet another embodiment, one or more calibration buttons may be placed on the wireless microphone. One means to communicate the activation of calibration buttons placed on the wireless microphone is to discontinue the radio broadcast from the wireless microphone for a preset time period, where the length of time for the time period corresponds to the calibration button activated. For example, a 100 milliseconds broadcast discontinuity corresponds to a first button, 200 milliseconds to a second button, and 300 milliseconds to a third button. In yet another embodiment placing calibration buttons on the microphone uses the audio channel itself to provide the button activation signal. Such a signal could be within the human audible frequency range, or outside the human audible frequency range.
For systems that involve more than two channels, the embodiments described herein are scaled up in manner understood by one trained in the art. Determining the position and relative outputs for two channels is typically linear, or close to linear, including gain and offset adjustments. Determining the position and relative output for more than two channels is typically more complex. Position may be determined by well-known triangulation techniques, by Gaussian techniques, by most-likely calculations, by calibration points, by manual entry of points, or by automatic memorization of a performer's movement pattern. Recreating correct apparent audio position for two or three dimensions of performer movement depends heavily on speaker placement. Persons trained in the art will recognize the methods of determining and creating apparent audio position and will be qualified to setup, adjust and calibrate such a system that uses more than two channels.
We have discussed this invention so far in terms of a live performance with live listeners in the audience of the performance. However, all aspects of this invention and its various embodiments apply equally to broadcast performances, such as via wire, cable, radio, television, satellite or the web, and also to performance recordings of all kinds. Thus, the perceived audio position of the performer may be live in person, live at a distant location, or later in time.
Although we have talked about performers on a stage, this invention is also applicable to other applications, such as police, fire or safety workers. Workers on a bridge, in a mine, on platforms, on a roadway, at a fire, in a police action, or in other working environments may use a wireless microphone, a radio, or a phone to communicate with other workers. There is an obvious advantage for the other workers to have an immediate sense of where the speaker is located by listening to the apparent source of the voice.
In one embodiment the position information is derived from the amplitude of the carrier signal of a wireless microphone. In another embodiment the position information comes from an RF time-of-flight device, ideally from a transmitter worn by the performer to one or more receivers located in the stage area. RF spread-spectrum technology may be used. In another embodiment the position information comes from an optical time-of-flight device, ideally from one or more transmitters worn by the performer to a plurality of receivers located in the stage area. In another embodiment, the position information comes from audio delay, cycle count and/or phase information from an audio, sub-audio, or ultrasonic transmitter, ideally worn by the performer to one or more audio receivers located in the stage area. It is particularly valuable, in some applications, to have the transmitter located in or with the wireless microphone. However, for some applications, such as those where a wireless microphone is not used, such as in ballet, ice-skating, and sports, the performer may wear a transmitter. In other embodiments, however, the position information of microphone or performer could come from other sources. For example, an observer could have an input device, such as a joystick, which the observer adjusts to provide a position signal to this invention based on the observer's observed position of a performer. This manual input approach may be appropriate when other, more automated position detection is impractical or not economical. For example, if the performer is an animal or is under water. One automatic means is to use a vision-based system which tracks the performer based on a video signal. Such tracking systems are widely used and known in the art. Another automatic means is to use an optical system with an optical transmitter on the performer. Another automatic means is to use a device containing both a position sensor, such as a GPS receiver, differential GPS, or other detector plus a wireless communication means such as Bluetooth, Wi-Fi, cellular data, or other communication means. This position-sensing device then detects and transmits the location of the performer, which is then used to determine the relative position of the performer on the stage. Such position sensing means may be either active or passive systems. Yet another automatic means is to detect the position of the performer from the mechanical position of a follow-spot. By monitoring the two-axis of motion of the follow spot, plus the use of basic trigonometry, it is simple to calculate the actual position of the follow-spot upon a surface. A cable or wireless communication may be used to communicate the position information from the follow-spot to the device, system or method of this invention. Even if the follow-spot has a human operator, no additional operator or manual input is required for this invention to be operational.
Two or even three dimensions of position information may be used with this invention. Additional speakers channels may be used, but are not required. For example, consider a deep stage. As the performer moves to the rear of the stage, the amplitude to both the left and right channels may be reduced, thus provide the effect to the listener that the performer is farther away. As another example, consider an ice skater on a large rink. The skater may be performing to a recording, in this example. By the use of multiple speakers, it is possible by using this invention to create an effect for the audience that the recorded sound, such as a singing voice, is coming from the ice skater. A similar example is an athlete on a large field, track or venue. A similar example is a racecar driver on a track. The sound source could be from the source in real-time, such as a roving singer, and acrobat or clown, or an animal. Or, the sound could be pre-recorded. For example, recorded sounds of a dog yelping could be played, using this invention to track one or more dogs around a track, where the audience hears the yelping as if coming from one or more running dogs.
An example of a three dimensional application is a circus. Performers may be high in the tent, or in the audience. By providing three dimensions of position information and a sufficient number of speakers the people in the audience can be given the impression that the sound is coming from anywhere within the 3D venue, or even outside the venue.
Creating an apparent position of a sound source between two speakers is a known problem in the art. One term for this is “stereo imaging,” often in the context of producing the “correct” apparent position of the sound source, where correct means the desired position. There are multiple algorithms for starting with a monaural source and allocating a percentage of the amplitude of that source to the two speakers, which for convenience in this section of the discussion we also call the left speaker and right speaker. One known algorithm is called, “constant power panning,” where the term panning refers to moving the apparent source from the left to the right speaker or vice versa. Constant power refers to the goal of having the sum or the power in the left speaker plus the power in the right speaker a constant value, relative to a fixed amplitude source and variable panning. Implementing constant power panning typically uses the algorithm where the voltage amplitude to the left channel is the square root of the desired position, where full left is equal to zero and full right is equal to one, and one represents 100% of the desired maximum voltage. The voltage the right channel is the square root of one minus the desired position, now expressed in the range of one down to zero. The power to a fixed impedance speaker is the square of the input voltage.
This particular algorithm for implementing constant power panning is shown below in Table 1. Other algorithms for creating an apparent position of a sound source between two speakers are known and may be used. Some algorithms incorporate a logarithmic relationship between position and voltage. Others use transcendental functions. Others use a triangulation approach involving the apparent positions and the listener position. Hybrid algorithms may be used. Empirically determined relationships may also be used. Implementation of the chosen algorithm may be implemented with analog electronics, digital computation. Implementation may use lookup tables.
The necessary amplitude computation, generation or lookup does not need to be particularly good in order to create an effective apparent position for a listener. Errors of 30% of amplitude may be adequate. Errors of 10% of less, for many applications will produce an effective result. Higher accuracy will, in some cases, produce a higher quality effective imaging. Accuracy worse than 30% will still produce some desired effect. Thus, effective implementation of this invention does not necessarily require any correction or linearization of a non-linear position input, such as an AGC control voltage, nor requires constant power panning implementation.
It is commonly regarded that an apparent doubling of sound volume requires approximately 10 dB more speaker power. Sound energy declines approximately with the square of the distance between the speaker and the listener. However, this approximation may be off due to the three-dimensional, spherical dispersion of sound energy from the speaker and may be off due to reflection of sound energy within the performance arena. There are also triangulation effects because frequently the listener is not a constant distance from both the speakers and the desired apparent position. As one trained in the art will appreciate, there are numerous ways to correct for or improve upon stereo imaging taking one or more of these site specific, application specific, sound type specific, or personal preferences into account.
An implementation may include additional features. For example, it may be desirable to average, filter or limit the speed of change of the position input signal. Variations in RF signal amplitude, and other factors may cause artifacts in the reported position of the performer or microphone. These artifacts may be reduced or mitigated by such averaging, filtering or speed of change limiting.
The left 7 and right 8 speakers provide audio information in two corresponding sound patterns 12 and 13. These sound patterns overlap in an idealized listening area traditionally located approximately equidistant from the two speakers. This listening area is sometimes called the “sweet spot” by those trained in the art. Listener 6 is shown in the preferred sound pattern overlap, which has the best “stereo imaging,” to use a common term in the art.
The purpose of stereo imaging is to provide the listener 6, or any listener in the listening area 5, which may be remote in space or time from the performance itself, with a sense that the location of the performer 1 on the stage 3 is close to actual location of the performer on the stage. For a two channel system, this stereo imaging effect is limited to a line between the left speaker 7 and the right speaker 8, which corresponds in general to the available positions on the stage for the performer between the two stage boundaries 10 and 11 respectively.
In the prior art, the use of a single channel wireless microphone 2 provided only a single channel of audio. This channel has normally, in the prior art, been mixed for equal volume to both the left and right channels, providing a stereo imaging effect for the listener that the performer is always in the center of the stage, no matter where the performer is actually on the stage. Although a sound designer or other person trained in the art may choose to mix the single channel of audio from the wireless microphone unequally to the left and right channels, thus placing via stereo imaging the effect of having the performer located some other place on the stage other than the center of the stage, this location is still fixed, providing no realistic sense to the listener as the performer moves around on the stage. Alternatively, in the prior art, a sound person or other operator could dynamically change the mix to affect the stereo imaging, but this effect would be done manually, not automatically.
This invention uses position information about the performer or the wireless microphone to provide an appropriate and effective stereo imaging effect while still using only a single audio channel from the wireless microphone, or a single channel of audio from another source. For example, a performer could be live, but the audio could be recorded. By using the position information from the live performer the effect of a live performance, rather than a recorded performance is superior.
The amplitude of the carrier input 51 depends, upon other things, the distance of the wireless microphone from the receiver. This amplitude decreases, typically, approximately as the square of the distance. However, there may be significant variations, either higher or lower, from this relationship. Nonetheless, except in pathological cases the amplitude of the carrier input 51 decreases with distance. Thus, the ADC control signal 56 comprises some information about the distance between the wireless microphone and the receiver. In one embodiment, usable distance information is extracted from this signal. Note that implementations of ADCs vary widely. The signals involved may vary significantly in amplitude, range, offsets and sign. They may be voltages or currents. They may be analog or digital signals.
Continuing with details shown in
Continuing with details shown in
A power supply 69 of any form or forms provides power to the components of this circuit.
Note that the elements 60, 64, 65 and the signals 59, 61, 63, 66, and 67 may be used in an alternative embodiment using an alternative position input signal 68 that does not come from an internal ADC within one receiver.
Note that as before, the designations, “left” and “right” are arbitrary. Note that more than two audio channels may be output if more than a single scalar position input is available. Note that as before, any or all or any combination of signals may be analog or digital.
The elements of the circuitry shown in
Note that we do not show in this circuit or in other circuits minor, typical, common and required elements for implementation or irrelevant features of analog electronics or signal processing, including amplification, buffering, range shifting, offsets, filtering, range limiting, selection, multiplexing, or decimation or supersampling in the case of digital signals. Such elements are well understood by those trained in the art and are not relevant to the logical functioning of the circuitry of this invention.
Note also that the audio outputs 66 and 67 may be voltages, currents, power, or any other form representing one channel of audio information each, including both analog and digital. These audio outputs 66 and 67 may be multiplexed or encoded, and thus are not necessarily on distinct wires.
To produce constant power panning, where the power is the square of the output voltage amplitudes of the channels, requires taking the square root of the voltage before allocating that fixed amplitude to the two channels. One such embodiment of one such circuit is shown in
Table 1 shows in tabular form the relationship between voltage and power for an exemplary two channels. The second row of this table shows the respective signal points in the circuit of
Continuing with the circuit in
Note that as before, the designations, “left” and “right” are arbitrary. Note that more than two audio channels may be output if more than a single scalar position input is available. Note that as before, any or all or any combination of signals may be analog or digital. Note that the ranges of signals shown in Table 1 are exemplary only and arbitrary.
For some embodiments the use of a square root function in the circuit is neither required nor desired. Constant power panning may be achieved in other ways. Or, constant power panning may not be desired at all. This square root function may not be shown for all circuits or examples herein. The square root function may be included in other modules, such as within a VGA module, or within an amplitude-shaping module. Note also that implementation of a square root module may not need to be precise. For example, use of logarithmic amplifier may, for some embodiments or some applications, provide a suitable implementation of a square root function over the desired signal range.
Note that it is not necessary to have the two receivers precisely at the first and second locations that are desired to use as endpoints for the generated or perceived stereo imaging effect. As discussed elsewhere, gain and offset controls, as well as calibration and other mechanisms and adjustments may be used to compensate of variations in the locations of the primary and secondary receivers relative to the desired first and second positions.
In
One or more power sources, 69, provide power to these components.
As before, the designations, “left” and “right” are arbitrary. Note that more than two audio channels may be output if more than a single scalar position signal 61 is available. Note that as before, any or all or any combination of signals may be analog or digital.
Table 2 below shows one possible implementation of a gain control. A gain setting of zero is neutral.
The Table 3 below shows one possible implementation of an offset control. An offset setting of zero is neutral.
Both gain and offset, if implemented, are meant to be variable controls.
Note again, that “left” and “right” are arbitrary.
In
There are many other possible ways to implement the features of gain and offset, as those trained in the art will appreciate. All signals may be either analog or digital. The controls may be continuous or discreet. The controls may be mechanical or electronic. They may be implemented via icons or other human input means from an electronic interface device.
There are many methods of communicating calibration or button activation information from the wireless microphone. For example, a sub-audio tone, such as below 20 Hz, could be used, with different frequencies, burst lengths or patterns for different buttons. Alternatively, a super-audio tone, such as above 20,000 Hz, could be used. Alternatively, the carrier could be turned of a period of time. As one trained in the art appreciates, there are many other methods for communicating calibration or button activation information from the wireless microphone.
Let us now use some equations to define one embodiment of this invention. A performance space is defined with a first position P1 we also refer to as left and a second position P2 we refer to as right. A sound source, such a wireless microphone or a performer is at physically at position PS located on a line between P1 and P2. We also call the sound source the performer. The distance from P1 to PS is D1. The distance from PS to P2 is D2. The distance from P1 to P1 is DS. D1+D2=DS. A left speaker is on the left side of the performance area near P1. A right speaker is on the right side of the performance area near P1. We define the amplitude of the sound from the left speaker as A(L) and the amplitude of the sound from the right speaker as A(R). For a constant perceived amplitude of sound for a listener who can hear both speakers, as the apparent sound source varies between left and right, we want A(L)+A(R)=A(C), where A(C) is a constant. In one embodiment A(L)=k1*D2 and A(R)=k2*D1; k1 and k2 are constants that convert units of distance to units of amplitude. In a preferred embodiment, k1=k2. The amplitudes, such as A(L) and A(R) may be power, voltage, dB, sound pressure, or some other appropriate measure of perceived audio amplitude.
Let us now use some different equations to define a second embodiment of this invention. A performance space is defined with a first position P1 we also refer to as left and a second position P2 we refer to as right. A sound source, such a wireless microphone or a performer is at physically at position PS located on a line between P1 and P2. We also call the sound source the performer. The distance from P1 to PS is D1. The distance from PS to P2 is D2. The distance from P1 to P1 is DS. D1+D2=DS. A left speaker is on the left side of the performance area near P1. A right speaker is on the right side of the performance area near P1. We define the amplitude of the sound from the left speaker as A(L) and the amplitude of the sound from the right speaker as A(R). For a constant perceived amplitude of sound for a listener who can hear both speakers, as the apparent sound source varies between left and right, we want A(L)+A(R)=A(C), where A(C) is a constant. In this second embodiment A(L)=k3/D1 and A(R)=k4/D2; k3 and k4 are constants that convert units of distance to units of amplitude. In a preferred embodiment, k3=k4. The amplitudes, such as A(L) and A(R) may be power, voltage, dB, sound pressure, or some other appropriate measure of perceived audio amplitude.
Let us now use some yet different equations to define a third embodiment of this invention. A performance space is defined with a first position P1 we also refer to as left and a second position P2 we refer to as right. A sound source, such a wireless microphone or a performer is at physically at position PS located on a line between P1 and P2. We also call the sound source the performer. The distance from P1 to PS is D1. The distance from PS to P2 is D2. The distance from P1 to P1 is DS. D1+D2=DS. A left speaker is on the left side of the performance area near P1. A right speaker is on the right side of the performance area near P1. We define the amplitude of the sound from the left speaker as A(L) and the amplitude of the sound from the right speaker as A(R). For a constant perceived amplitude of sound for a listener who can hear both speakers, as the apparent sound source varies between left and right, we want A(L)+A(R)=A(C), where A(C) is a constant. In this third embodiment A(L)=k5*D2/D1 and A(R)=k6*D1/D2; k5 and k6 are constants that convert units of distance to units of amplitude. In a preferred embodiment, k5=k6 The amplitudes, such as A(L) and A(R) may be power, voltage, dB, sound pressure, or some other appropriate measure of perceived audio amplitude.
Most discussion herein has referred to a single wireless microphone. In many performances, more than one wireless microphone is often used. Nothing in this description or claims precludes multiple instances of this invention, or multiple instances of portions of this invention to achieve position information for multiple wireless microphone or multiple performers. For example, a single receiver is often capable of receiving signals from more than one wireless microphone.
We have described embodiments using physical devices in a physical environment. This invention works equally well when some or all of the components are wholly or partially implemented digitally using software, digital electronics, digital signal processing or by other means. This invention works equally well some or all of the components are implemented in a distributed fashion.
“Amplifier”—An amplifier is an electronic device that takes an input signal of one amplitude or format and produces an output signal of higher amplitude or different format or impedance. In audio performances, amplifiers are used in multiple locations for multiple purposes. A microphone pre-amplifier takes the electrical output from a microphone as input and produces a relatively “standard” voltage and impedance output, often measured in dBu or dBV, or measured in dB relative to 0.775 volts RMS. Sometimes standard audio signals are measured as power, where 0 dBm represents one milliwatt into a 600 ohm load. A peak signal maybe approximately +4 dBu or −10 dBV. One trained in the art will appreciate these units and metrics. A mixer might have both microphone inputs and “standard” inputs. It will typically produce “standard” outputs as defined above. A speaker amplifier or power amplifier takes “standard” inputs as defined above and produces signals of appropriate voltage, current, impedance and power to drive one or more speakers. Microphone preamplifiers, mixers, and power amplifiers exist in wide range of packaging and performance capabilities. An RF amplifier, such as is typically found in a wireless microphone receiver, amplifies radio frequency signals. An RF amplifier may incorporate an AGC, or the AGC may be separate from the RF amplifier.
“Audio”—An audible sound.
“Audio representation”—refers to the rendering of an electrical audio signal by a speaker, headphone, or similar device to produces sound, or to the generation of an electrical audio signal by a microphone or similar device in response to a sound. The universal goal of audio representation is fidelity, meaning the accurate conversion of the electrical signal to sound and vice versa without the introduction of any artifacts such as distortion, noise, inappropriate phase shift or inappropriate delay.
“Audio signal”—primarily amplitude, but ideally phase information is also included as part of an audio signal for the best possible audio fidelity. Signal delay may be a critical aspect of an audio signal. A single audio signal may be a low level signal of type similar to the output of a microphone, or a low level signal of type similar to traditional audio signals used within mixers and as inputs to power amplifiers, or a power signal designed to drive a speaker, or some other suitable signal containing audio information, including a wide range of digital audio signal formats, including but not limited to PCM formats, CD format, DVD format, HDMI format, MP3, Advanced Audio Coding, Ogg Vorbis, FLAC format, .wav, .mid, .ra, ram, Wma, format, aiff format, and many more, including both compressed and non-compressed, lossless and lossy formats, encrypted and non-encrypted, pure audio and audio with other information included in the format, such as video information, both file formats and streaming formats.
“Audience”—One or more listeners.
“Automatic Gain Control,” or “AGC”—A circuit that accepts an input signal of wide amplitude variation and provides an output signal of relatively consistent amplitude. AGCs are used for both audio signals and for RF signals. In mode embodiment an AGC works by averaging the amplitude of an input signal and using that average to then control a variable gain amplifier (VGA), which then in turn amplifies the input signal, a variable amount. In another embodiment of an AGC the output of the VGA is averaged and then used that as a control signal for the VGA. In either embodiment the control signal to the VGA reflects the amplitude of the input signal. These and other implementations of AGC circuits are common and well known to those skilled in the art.
“Calibration”—The process of calibrating the actual position of wireless microphone or a performer to cause the invention to create an audio apparent position, or stereo image, of the microphone or performer at a present position. If a single calibration point is used, which may be set by the activation of a button, the typical implementation would assure that the one preset position is produced accurately by adjusting either the gain, offset, or both. Positions other than the one preset position may not be produced accurately. If two calibrations points are used, which may be set by activating two buttons, then these two preset positions are produced accurately, typically by adjusting both the gain and offset. If three calibration points are used, which may be set by activating three buttons, then these three preset positions are produced accurately. In one preferred embodiment for a one-button system the preset position is the center of the performance area. In one preferred embodiment for a two-button system the preset positions are the left and right of the performance area. In one preferred embodiment for a three-button system the preset positions are the left, right and center of the performance area. One trained in the art will appreciate that there are many other ways to accomplish calibration besides the use of one or more buttons. If buttons are used for calibration, one embodiment places the buttons on one receiver, two receivers, or on the wireless microphone, in any combination. Such a location or locations for the button or buttons provides convenience for the performer or the person setting up the sound for a performance. If any of the buttons are physically located at or near the preset position represented by that button, the calibration using such a button or buttons is intuitive. For example, a button located on a receiver placed at the left side of the stage could create a calibration point at the left side of the stage. A button on the wireless microphone creates a simple way to create a calibration point for the center of the performing area.
“Channel”—An audio channel generally contains one monaural signal. The term channel may refer to an end-to-end path, such as from a microphone, through a pre-amp, through a mixer, through a power amp, and then to a speaker. Or, it may refer to a single point or single path segment within a longer end-to-end channel. For example, a mixer specification normally refers to its maximum number of inputs as channels. While a channel in a professional audio context normally refers to a specific signal or specific cable or cable connection, it may also refer to group of related signals. For example, the “left channel” might actually consist of three separate channels, a high-frequency channel, a mid-frequency channel, and a low-frequency channel, all going to a related speaker set or speaker assembly that in aggregate is known as the “left speaker.” Thus, for example in this invention, the modulator may produce a single standard output identified as the “left channel,” which after it passes through a mixer/amplifier becomes three separate channels going to physical speakers.
“Increase” or “Decrease” in amplitude—Functions are described that have an inverse relationship such that as one function increases in value a second function decreases in value. These inverse relationships, the functions, and the increases and decreases in value are not absolute relationships with no deviation whatsoever, but rather a substantial relationship that accommodates minor, temporary, trivial, artificial, or insignificant variations from this relationship. The necessary accuracy of amplitudes is such that an ordinary listener would perceive the desired effect.
“Listeners, or audience, or audience members”—One or more listeners, when the invention is in use, has the perception as to the location of the sound between two speakers or speaker systems, or in an area bounded by multiple speakers or speaker systems.
“Mixer”—A mixer is a common professional audio component. A mixer typically takes as in put a large number of discreet channels and provides a smaller number of outputs, where generally, each output is intended for specific speaker after first passing from the mixer through a power amplifier. Mixers often include optional microphone pre-amplifiers. Mixers usually have volume controls, or “gain” controls for most input and output channels. Mixers may optionally have many other features, such as amplitude meters or setup memory.
“On the stage”—includes a traditional stage, position being primarily as single vector incorporating information towards stage left or towards stage right. However, the term “on the stage” could also include X-Y coordinates to indicate also position towards the back of the stage versus position towards the front of the stage. In addition, the term “on the stage” explicitly includes off the stage positions, such as off stage left, off-stage right, back stage, or in the audience. In addition, the phrase include three-dimensional information such as up in the air or beneath the stage. A stage may be any performance arena, including a sports field, or a virtual area.
“Performer”—user of the wireless microphone. Typically, a single person, who may be singing or talking or playing a musical instrument. However, the performer could be more than one person or more than one instrument. The performer is anyone or anything that produces the primary sound picked up by the wireless microphone. A performer may be an animal.
“Position or location on the stage”—this includes the position of the performer on the stage relative to stage left or stage right, but also includes positions completely off the stage, including offstage left or offstage right, and in the audience, or behind the stage. It could include three-dimensional information such as performers in the air. Such 3D positioning could be particularly appropriate for certain stage products as musicals, circuses, acrobatics, aeronautics, military productions or magic shows.
“Speakers”—Speaker are audio component that take an electrical audio signal as input and generate sound to correspond to the audio signal. Most speakers are designed to operate in the range of human audible frequencies, however, some speakers, such as sub-woofers and ultra-sonic transducers are able to operate outsider this frequency range.
“Splitter”—A generic term for a device that takes one audio input and produces two or more audio outputs.
“Stage”—The stage may be a physical stage, with a performer and a wireless microphone on the stage, with an audience in front of the stage, or it may be any space defined to contain a line between two points or a plane with more than two points on which a wireless microphone may be located.
“Stereo imaging”—the impression a listener has about the apparent physical location of the sound source, as create the outputs of two or more fixed-location speakers.
“Stereo, two channels, or left and right channels”—This is the traditional audio configuration designed to produce an apparent audio position of sound sources along a one-dimensional line stretches approximately from the left speaker location to the right speaker location. For many audio performances, the left and right speakers are located close to the stage left and stage right position, so that the possible physical range for performers on the stage proper is close to the range for the apparent audio position from these speakers.
“Switch”—A device which may be activated by a person, such as a mechanical button, which has two or more discreet states. For a two state device, the states may be identified as on or off. For a two-state switch which automatically returns to its first state, the switch may be identified as a momentary switch. The switch may be mechanical, electronic, or an icon or other input means on a human interface device. For examples, the switch may be a soft button on the touch-screen of a portable electronic device, or it could be a mechanical push button on a wireless microphone receiver.
“Wireless microphone”—A monaural or stereo audio component, with an audio sensor, that transmits the audio information received by the sensor to a separate, associated receiver without the use of a connecting wire between the microphone and receiver. The wireless microphone and the associated receiver may use radio waves or light waves as a transmission medium. The term, microphone, usually refers only to the portable component with the audio sensor. However, wireless microphones are usually sold as a system containing one or more wireless microphones with one or more matching receivers. The microphone component is commonly handheld, however it may be adapted for use as a headset or it may be clipped on an article of clothing, or it may be attached to or integrated into a musical instrument. Other mountings and applications are common. For the wireless microphone to be used as part of a full audio system both the microphone component and the associated receiver component as usually used together.
