Patent Publication Number: US-2021195358-A1

Title: Controlling audio rendering

Description:
TECHNOLOGICAL FIELD 
     Embodiments of the present invention relate to controlling audio rendering. In particular, they relate to controlling audio rendering of a sound scene comprising multiple sound objects. 
     BACKGROUND 
     A sound scene in this document is used to refer to the arrangement of sound sources in a three-dimensional space. When a sound source changes position, the sound scene changes. When the sound source changes its audio properties such as its audio output, then the sound scene changes. 
     A sound scene may be defined in relation to recording sounds (a recorded sound scene) and in relation to rendering sounds (a rendered sound scene). 
     Some current technology focuses on accurately reproducing a recorded sound scene as a rendered sound scene at a distance in time and space from the recorded sound scene. The recorded sound scene is encoded for storage and/or transmission. 
     A sound object within a sound scene may be a source sound object that represents a sound source within the sound scene or may be a recorded sound object which represents sounds recorded at a particular microphone. In this document, reference to a sound object refers to both a recorded sound object and a source sound object. However, in some examples, the sound object may be only source sound objects and in other examples a sound object may be only a recorded sound object. 
     By using audio processing it may be possible, in some circumstances, to convert a recorded sound object into a source sound object and/or to convert a source sound object into a recorded sound object. 
     It may be desirable in some circumstances to record a sound scene using multiple microphones. Some microphones, such as Lavalier microphones, or other portable microphones, may be attached to or may follow a sound source in the sound scene. Other microphones may be static in the sound scene. 
     The combination of outputs from the various microphones defines a recorded sound scene. However, it may not always be desirable to render the sound scene exactly as it has been recorded. It is therefore desirable, in some circumstances, to enable a post-recording adaptation of the recorded sound scene to produce an alternative rendered sound scene. 
     BRIEF SUMMARY 
     According to various, but not necessarily all, embodiments of the invention there is provided a method comprising: remotely sensing a real acoustic environment, in which multiple audio signals are captured; and enabling automatic control of mixing of the multiple captured audio signals based on the remote sensing of the real acoustic environment in which the multiple audio signals were captured. 
     According to various, but not necessarily all, embodiments of the invention there is provided an apparatus comprising: at least one processor; and at least one memory including computer program code the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to perform: enabling automatic control of mixing of multiple captured audio signals based on remote sensing of a real acoustic environment in which the multiple audio signals were captured. 
     According to various, but not necessarily all, embodiments of the invention there is provided a computer program that when run on a processor performs: enabling automatic control of mixing of multiple captured audio signals based on remote sensing of a real acoustic environment in which the multiple audio signals were captured. 
     According to various, but not necessarily all, embodiments of the invention there is provided an apparatus comprisingL means for remotely sensing a real acoustic environment, in which multiple audio signals are captured; and means for automatically controlling mixing of the multiple captured audio signals based on the remote sensing of the real acoustic environment in which the multiple audio signals were captured. 
     According to various, but not necessarily all, embodiments of the invention there is provided examples as claimed in the appended claims. 
    
    
     
       BRIEF DESCRIPTION 
       For a better understanding of various examples that are useful for understanding the detailed description, reference will now be made by way of example only to the accompanying drawings in which: 
         FIG. 1  illustrates an example of a system and also an example of a method for recording and encoding a sound scene; 
         FIG. 2  schematically illustrates relative positions of a portable microphone (PM) and static microphone (SM) relative to an arbitrary reference point (REF); 
         FIG. 3  illustrates a module which may be used, for example, to perform the functions of the positioning block, orientation block and distance block of the system; 
         FIGS. 4A and 4B  illustrate examples of a direct module and an indirect module for use in the module of  FIG. 3 ; 
         FIG. 5  illustrates an example of the system implemented using an apparatus; 
         FIG. 6  illustrates an example of a method for enabling automatic control of mixing of multiple captured audio signals based on remote sensing of a real acoustic environment; 
         FIG. 7  illustrates an example of a system and also an example of a method for recording and encoding a sound scene by automatically conditioning an audio signal from a portable microphone in dependence on remote sensing of a real acoustic environment; 
         FIG. 8  illustrates a module which may be used, for example, to perform conditioning of an audio signal in dependence on remote sensing of a real acoustic environment; 
         FIGS. 9A, 9B  illustrates an example of automatic control of mixing of multiple captured audio signals based on remote sensing of a real acoustic environment, where the remote sensing is performed using transmission/reflection/reception of sensing signals; 
         FIGS. 10A, 10B &amp; 11A, 11B  illustrate examples of automatic control of mixing of multiple captured audio signals based on remote sensing of a real acoustic environment, where the remote sensing is performed using different sensing signals; 
         FIG. 12  illustrates an example of a multi-media rendering system. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates an example of a system  100  and also an example of a method  200 . The system  100  and method  200  record a sound scene  10  and process the recorded sound scene to enable an accurate rendering of the recorded sound scene as a rendered sound scene for a listener at a particular position (the origin) within the recorded sound scene  10 . 
     In this example, the origin of the sound scene is at a microphone  120 . In this example, the microphone  120  is static. It may record one or more channels, for example it may be a microphone array. 
     In this example, only a single static microphone  120  is illustrated. However, in other examples multiple static microphones  120  may be used independently. In such circumstances the origin may be at any one of these static microphones  120  and it may be desirable to switch, in some circumstances, the origin between static microphones  120  or to position the origin at an arbitrary position within the sound scene. 
     The system  100  also comprises one or more portable microphones  110 . The portable microphone  110  may, for example, move with a sound source within the recorded sound scene  10 . This may be achieved, for example, using a boom microphone or, for example, attaching the microphone to the sound source, for example, by using a Lavalier microphone. The portable microphone  110  may record one or more recording channels. 
       FIG. 2  schematically illustrates the relative positions of the portable microphone (PM)  110  and the static microphone (SM)  120  relative to an arbitrary reference point (REF). The position of the static microphone  120  relative to the reference point REF is represented by the vector  x . The position of the portable microphone PM relative to the reference point REF is represented by the vector  y . The relative position of the portable microphone  110  from the static microphone SM is represented by the vector  z . It will be understood that  z = y − x . As the static microphone SM is static, the vector  x  is constant. Therefore, if one has knowledge of  x  and tracks variations in  y , it is possible to also track variations in  z . The vector  z  gives the relative position of the portable microphone  110  relative to the static microphone  120  which is the origin of the sound scene  10 . The vector  z  therefore positions the portable microphone  110  relative to a notional listener of the recorded sound scene  10 . 
     There are many different technologies that may be used to position an object including passive systems where the positioned object is passive and does not produce a signal and active systems where the positioned object produces a signal. An example of a passive system, used in the Kinect™ device, is when an object is painted with a non-homogenous pattern of symbols using infrared light and the reflected light is measured using multiple cameras and then processed, using the parallax effect, to determine a position of the object. An example of an active system is when an object has a transmitter that transmits a radio signal to multiple receivers to enable the object to be positioned by, for example, trilateration. An example of an active system is when an object has a receiver or receivers that receive a radio signal from multiple transmitters to enable the object to be positioned by, for example, trilateration. 
     When the sound scene  10  as recorded is rendered to a user (listener) by the system  100  in  FIG. 1 , it is rendered to the listener as if the listener is positioned at the origin of the recorded sound scene  10 . It is therefore important that, as the portable microphone  110  moves in the recorded sound scene  10 , its position  z  relative to the origin of the recorded sound scene  10  is tracked and is correctly represented in the rendered sound scene. The system  100  is configured to achieve this. 
     In the example of  FIG. 1 , the audio signals  122  output from the static microphone  120  are coded by audio coder  130  into a multichannel audio signal  132 . If multiple static microphones were present, the output of each would be separately coded by an audio coder into a multichannel audio signal. 
     The audio coder  130  may be a spatial audio coder such that the multichannels  132  represent the sound scene  10  as recorded by the static microphone  120  and can be rendered giving a spatial audio effect. For example, the audio coder  130  may be configured to produce multichannel audio signals  132  according to a defined standard such as, for example, binaural coding, 5.1 surround sound coding, 7.1 surround sound coding etc. If multiple static microphones were present, the multichannel signal of each static microphone would be produced according to the same defined standard such as, for example, binaural coding, 5.1 surround sound coding, 7.1 and in relation to the same common rendered sound scene. 
     The multichannel audio signals  132  from one or more of the static microphones  120  are mixed by mixer  102  with multichannel audio signals  142  from the one or more portable microphones  110  to produce a multi-microphone multichannel audio signal  103  that represents the recorded sound scene  10  relative to the origin and which can be rendered by an audio decoder corresponding to the audio coder  130  to reproduce a rendered sound scene to a listener that corresponds to the recorded sound scene when the listener is at the origin. 
     The multichannel audio signal  142  from the, or each, portable microphone  110  is processed before mixing to take account of any change in position of the portable microphone  110  relative to the origin at the static microphone  120 . 
     The audio signals  112  output from the portable microphone  110  are processed by the positioning block  140  to adjust for a change in position of the portable microphone  110  relative to the origin at the static microphone  120 . The positioning block  140  takes as an input the vector  z  or some parameter or parameters dependent upon the vector  z . The vector  z  represents the relative position of the portable microphone  110  relative to the origin at the static microphone  120 . 
     The positioning block  140  may be configured to adjust for any time misalignment between the audio signals  112  recorded by the portable microphone  110  and the audio signals  122  recorded by the static microphone  120  so that they share a common time reference frame. This may be achieved, for example, by correlating naturally occurring or artificially introduced (non-audible) audio signals that are present within the audio signals  112  from the portable microphone  110  with those within the audio signals  122  from the static microphone  120 . Any timing offset identified by the correlation may be used to delay/advance the audio signals  112  from the portable microphone  110  before processing by the positioning block  140 . 
     The positioning block  140  processes the audio signals  112  from the portable microphone  110 , taking into account, for example, the relative orientation (Arg( z )) of that portable microphone  110  relative to the origin at the static microphone  120 . 
     The audio coding of the static microphone audio signals  122  to produce the multichannel audio signal  132  assumes a particular orientation of the rendered sound scene relative to an orientation of the recorded sound scene and the audio signals  122  are encoded to the multichannel audio signals  132  accordingly. 
     The relative orientation Arg ( z ) of the portable microphone  110  in the recorded sound scene  10  is determined and the audio signals  112  representing the sound object are coded to the multichannels defined by the audio coding  130  such that the sound object is correctly oriented within the rendered sound scene at a relative orientation Arg ( z ) from the listener. For example, the audio signals  112  may first be mixed or encoded into the multichannel signals  142  and then a transformation T may be used to rotate the multichannel audio signals  142 , representing the moving sound object, within the space defined by those multiple channels by Arg ( z ). 
     The portable microphone signals  112  may additionally be processed to control the perception of a distance D of the sound object from the listener in the rendered sound scene, for example, to match the distance | z | of the sound object from the origin in the recorded sound scene  10 . This can be useful when binaural coding is used so that the sound object is, for example, externalized from the user and appears to be at a distance rather than within the user&#39;s head, between the user&#39;s ears. The positioning block  140  modifies the multichannel audio signal  142  to modify the perception of distance. 
       FIG. 3  illustrates a module  170  which may be used, for example, to perform the functions of the positioning block  140  in  FIG. 1 . The module  170  may be implemented using circuitry and/or programmed processors. 
     The Figure illustrates the processing of a single channel of the multichannel audio signal  142  before it is mixed with the multichannel audio signal  132  to form the multi-microphone multichannel audio signal  103 . A single input channel of the multichannel signal  142  is input as signal  187 . 
     The input signal  187  passes in parallel through a “direct” path and one or more “indirect” paths before the outputs from the paths are mixed together, as multichannel signals, by mixer  196  to produce the output multichannel signal  197 . The output multichannel signal  197 , for each of the input channels, are mixed to form the multichannel audio signal  142  that is mixed with the multichannel audio signal  132 . 
     The direct path represents audio signals that appear, to a listener, to have been received directly from an audio source and an indirect path represents audio signals that appear to a listener to have been received from an audio source via an indirect path such as a multipath or a reflected path or a refracted path. 
     A distance block  160  by modifying the relative gain between the direct path and the indirect paths, changes the perception of the distance D of the sound object from the listener in a rendered sound scene. 
     Each of the parallel paths comprises a variable gain device  181 ,  191  which is controlled by the distance block  160 . 
     The perception of distance can be controlled by controlling relative gain between the direct path and the indirect (decorrelated) paths. Increasing the indirect path gain relative to the direct path gain increases the perception of distance. 
     In the direct path, the input signal  187  is amplified by variable gain device  181 , under the control of the distance block  160 , to produce a gain-adjusted signal  183 . The gain-adjusted signal  183  is processed by a direct processing module  182  to produce a direct multichannel audio signal  185 . 
     In the indirect path, the input signal  187  is amplified by variable gain device  191 , under the control of the positioning block  160 , to produce a gain-adjusted signal  193 . The gain-adjusted signal  193  is processed by an indirect processing module  192  to produce an indirect multichannel audio signal  195 . 
     The direct multichannel audio signal  185  and the one or more indirect multichannel audio signals  195  are mixed in the mixer  196  to produce the output multichannel audio signal  197 . 
     The direct processing block  182  and the indirect processing block  192  both receive direction of arrival signals  188 . The direction of arrival signal  188  gives the orientation Arg( z ) of the portable microphone  110  (moving sound object) in the recorded sound scene  10 . 
     The direct module  182  may, for example, include a system  184  similar to that illustrated in  FIG. 4A  that rotates the single channel audio signal, gain-adjusted input signal  183 , in the appropriate multichannel space producing the direct multichannel audio signal  185 . 
     The system  184  uses a transfer function to perform a transformation T that rotates multichannel signals within the space defined for those multiple channels by Arg( z ), defined by the direction of arrival signal  188 . For example, a head related transfer function (HRTF) interpolator may be used for binaural audio. 
     The indirect module  192  may, for example, be implemented as illustrated in  FIG. 4B . In this example, the direction of arrival signal  188  controls the gain of the single channel audio signal, the gain-adjusted input signal  193 , using a variable gain device  194 . The amplified signal is then processed using a static decorrelator  199  and then a system  198  that applies a static transformation T to produce the output multichannel audio signals  195 . The static decorrelator in this example uses a pre-delay of at least 2 ms. The transformation T rotates multichannel signals within the space defined for those multiple channels in a manner similar to the system  184  but by a fixed amount. For example, a static head related transfer function (HRTF) interpolator may be used for binaural audio. 
     It will therefore be appreciated that the module  170  can be used to process the portable microphone signals  112  and perform the function of changing the relative position (orientation Arg(z) and/or distance |z|) of a sound object, represented by a portable microphone audio signal  112 , from a listener in the rendered sound scene. 
       FIG. 5  illustrates an example of the system  100  implemented using an apparatus  400 , for example, a portable electronic device. The portable electronic device may, for example, be a hand-portable electronic device that has a size that makes it suitable to carried on a palm of a user or in an inside jacket pocket of the user. 
     In this example, the apparatus  400  comprises the static microphone  120  as an integrated microphone but does not comprise the one or more portable microphones  110  which are remote. However, in other examples the apparatus does not comprise the static microphone or microphones. In this example, but not necessarily all examples, the static microphone  120  is a microphone array. 
     The apparatus  400  comprises an external communication interface  402  for communicating externally to receive data from the remote portable microphone  110  and any additional static microphones or portable microphones. The external communication interface  402  may, for example, comprise a radio transceiver. 
     A positioning system  450  is illustrated. This positioning system  450  is used to position the portable microphone  110  relative to the static microphone  120 . In this example, the positioning system  450  is illustrated as external to both the portable microphone  110  and the apparatus  400 . It provides information dependent on the position  z  of the portable microphone  110  relative to the static microphone  120  to the apparatus  400 . In this example, the information is provided via the external communication interface  402 , however, in other examples a different interface may be used. Also, in other examples, the positioning system may be wholly or partially located within the portable microphone  110  and/or within the apparatus  400 . 
     The positioning system  450  provides an update of the position of the portable microphone  110  with a particular frequency and the terms ‘accurate’ and ‘inaccurate’ positioning of the sound object should be understood to mean accurate or inaccurate within the constraints imposed by the frequency of the positional update. That is accurate and inaccurate are relative terms rather than absolute terms. 
     The apparatus  400  wholly or partially operates the system  100  and method  200  described above to produce a multi-microphone multichannel audio signal  103 . 
     The apparatus  400  provides the multi-microphone multichannel audio signal  103  via an output communications interface  404  to an audio output device  300  for rendering. 
     In some but not necessarily all examples, the audio output device  300  may use binaural coding. Alternatively or additionally, in some but not necessarily all examples, the audio output device may be a head-mounted audio output device. 
     In this example, the apparatus  400  comprises a controller  410  configured to process the signals provided by the static microphone  120  and the portable microphone  110  and the positioning system  450 . In some examples, the controller  410  may be required to perform analogue to digital conversion of signals received from microphones  110 ,  120  and/or perform digital to analogue conversion of signals to the audio output device  300  depending upon the functionality at the microphones  110 ,  120  and audio output device  300 . However, for clarity of presentation no converters are illustrated in  FIG. 5 . 
     Implementation of a controller  410  may be as controller circuitry. The controller  410  may be implemented in hardware alone, have certain aspects in software including firmware alone or can be a combination of hardware and software (including firmware). 
     As illustrated in  FIG. 5  the controller  410  may be implemented using instructions that enable hardware functionality, for example, by using executable instructions of a computer program  416  in a general-purpose or special-purpose processor  412  that may be stored on a computer readable storage medium (disk, memory etc) to be executed by such a processor  412 . 
     The processor  412  is configured to read from and write to the memory  414 . The processor  412  may also comprise an output interface via which data and/or commands are output by the processor  412  and an input interface via which data and/or commands are input to the processor  412 . 
     The memory  414  stores a computer program  416  comprising computer program instructions (computer program code) that controls the operation of the apparatus  400  when loaded into the processor  412 . The computer program instructions, of the computer program  416 , provide the logic and routines that enables the apparatus to perform the methods illustrated in  FIG. 1-12 . The processor  412  by reading the memory  414  is able to load and execute the computer program  416 . 
     As illustrated in  FIG. 5 , the computer program  416  may arrive at the apparatus  400  via any suitable delivery mechanism  430 . The delivery mechanism  430  may be, for example, a non-transitory computer-readable storage medium, a computer program product, a memory device, a record medium such as a compact disc read-only memory (CD-ROM) or digital versatile disc (DVD), an article of manufacture that tangibly embodies the computer program  416 . The delivery mechanism may be a signal configured to reliably transfer the computer program  416 . The apparatus  400  may propagate or transmit the computer program  416  as a computer data signal. 
     Although the memory  414  is illustrated as a single component/circuitry it may be implemented as one or more separate components/circuitry some or all of which may be integrated/removable and/or may provide permanent/semi-permanent/dynamic/cached storage. 
     Although the processor  412  is illustrated as a single component/circuitry it may be implemented as one or more separate components/circuitry some or all of which may be integrated/removable. The processor  412  may be a single core or multi-core processor. 
     The foregoing description describes a system  100  and method  200  that can position a sound object within a rendered sound scene. The system as described has been used to position the sound source within the rendered sound scene, so that the rendered sound scene accurately reproduces a position of the sound source in the recorded sound scene. The inventors have realized that the recorded sound scene may not accurately represent a sound scene that would be heard by an observer at the origin of the rendered sound scene. This may be because the acoustic environment of the sound scene from the perspective of the origin of the rendered sound scene is different than the acoustic environment of the sound scene from the perspective of the microphones recording the sound scene. 
     For example, referring back to  FIG. 2 , there is a direct path from a sound source at the portable microphone PM to the origin of the rendered sound scene at the static microphone SM. The sound scene heard by an observer at the origin would change depending upon whether or not there is an obstruction in that path. The system  100  described thus far does not account for the effect of such an obstruction. Rendering the sound scene without taking into account the obstructed path means that the sound scene rendered will not be an accurate reproduction of the sound scene from the position of the origin. This may, for example, be important if a user is simultaneously viewing a video of the scene from the position of the origin while listening to the rendered sound scene from that position. There will be a mismatch between the scene as viewed and as heard. For example when a sound source associated with the portable microphone (PM)  110  moves behind a wall so that it is no longer visible from the origin in the video, then the visual scene changes but the rendered sound scene does not. This problem is addressed below. 
       FIG. 6  illustrates an example of a method  500  for enabling automatic control of mixing of multiple captured audio signals. 
     At block  502 , the method  500  comprises remotely sensing a real acoustic environment, in which multiple audio signals are captured. 
     At block  504 , the method comprises enabling automatic control of mixing of the multiple captured audio signals based on the remote sensing of the real acoustic environment in which the multiple audio signals were captured. 
     The method  500  enables the correct rendering of sound objects from a perspective of an origin of a rendered sound scene taking into account the real acoustic environment of the sound object in the recorded sound scene  10 . The listener to the rendered sound scene hears the recorded sound scene as if they were positioned at the origin of the rendered sound scene in the recorded sound scene  10 . The rendering takes into account the real acoustic environment of the sound object and adapts to changes in the real acoustic environment of the sound object. 
       FIG. 7  illustrates an example of the system  100  previously described in relation to  FIG. 1 . However, in this example of the system  100 , the positioning block  140  has been replaced by conditioning block  740 . 
     The conditioning block  740  is configured to operate in the same manner as the positioning block  140  when there is no requirement to automatically control mixing of the multiple captured audio signals  142 ,  132  based on remote sensing of the real acoustic environment. However, when there is a requirement to control mixing of the multiple captured audio signals  142 ,  132  based on the remote sensing of the real acoustic environment, then the conditioning block  740  conditions the audio signals  112  recorded by the portable microphone  110  in a manner different to that performed by the positioning block  140 . 
     The conditioning block  740  may be configured to adjust for any time misalignment between the audio signals  112  recorded by the portable microphone  110  and the audio signals  122  recorded by the static microphone  120  so that they share a common time reference frame. This may be achieved, for example, by correlating naturally occurring or artificially introduced (non-audible) audio signals that are present within the audio signals  112  from the portable microphone  110  with those within the audio signal  122  from the static microphone  120 . Any timing offset identified by the correlation may be used to delay/advance the audio signals  112  from the portable microphone  110  before processing by the conditioning block  740 . 
     The system  100  illustrated in  FIG. 7  is similar to the system  100  illustrated in  FIG. 1  in that audio signals  112  output from the portable microphone  110  are processed by the conditioning block  740  to adjust the audio signals  112 . As illustrated in  FIG. 7 , the conditioning block  740  takes as an input a position  741  of the portable microphone  110 , for example, the vector  z  or some parameter or parameters dependent upon the vector  z . The vector  z  represents the relative position of the portable microphone  110  relative to the origin (the static microphone  120 ). 
     The acoustic environment sensor  750  may be, for example, at the origin of the rendered sound scene, for example, at the static microphone  120 , or it may be positioned elsewhere but provide information about the real acoustic environment of the portable microphone  110  from the perspective of the origin of the rendered sound scene. 
     The real acoustic environment is the physical environment. The real acoustic environment from the perspective of the origin of the rendered sound scene is the physical environment that impacts acoustically upon sound travelling from the sound object (e.g. the portable microphone  110 ) to the origin of the rendered sound scene, which in some examples may be at the position of the static microphone  120 . The real acoustic environment may, for example, impact upon the number and quality of acoustic paths for sound to travel from the sound object (e.g. at the portable microphone  110 ) to the origin of the rendered sound scene. 
     The conditioning block  740  takes as a further input sensor information  742  relating to sensing of a real acoustic environment by the acoustic environment sensor  750 . 
     The conditioning block  740  processes the audio signals  112  from the portable microphone  110  taking into account, for example, the relative orientation (Arg( z )) of the portable microphone  110  relative to an origin of the rendered sound scene, the relative distance | z | of the portable microphone  110  relative to the origin of the rendered sound scene, and the sensed real acoustic environment of the portable microphone  110  relative to the origin of the rendered sound scene. 
     The conditioning block  740  is used to control mixing of the multi-channel audio signal  142  and the multi-channel audio signal  132  by conditioning the multi-channel audio signal  142 , representing the moving sound object, to compensate for the real acoustic environment of the moving sound object. 
     The conditioning by conditioning block  740  may occur in real time commensurate with the capturing of the audio signals  112  by the portable microphone  110  or it may occur at a later time using a recorded version of the portable microphone signals  112  and corresponding recorded values of the position  741  of the portable microphone  110  and the recorded sensor information  742  for the real acoustic environment of the portable microphone  110 . The conditioning performed by the conditioning block  740  may therefore be shifted in time and space relative to the capturing of the portable microphone signals  112  and/or relative to the rendering of the sound scene. 
     In some but not necessarily all examples, the acoustic environment sensor  750  may be configured to sense all or part of a real ambient acoustic environment of the portable microphone  110  (sound object). The real ambient acoustic environment is the environment that impacts upon the likelihood of sound recorded by the portable microphone  110  reaching the origin of the rendered sound scene by multi-paths, for example, by reflection off neighboring objects, walls, ceilings, etc. The acoustic environment sensors  750  may sense the real ambient acoustic environment by, for example, transmitting sensing signals into the real acoustic environment and detecting the reflection of the sensing signals from the real acoustic environment. The detection of such reflected sensing signals may enable the conditioning block  740  to map at least some of the real acoustic environment. In this way, it may be possible for the conditioning block  740  to determine when a particularly sound-absorbing environment is near to/behind the portable microphone  110  but is not obstructing a direct path from the portable microphone  110  to the origin of the rendered sound scene. In this scenario, the conditioning block  740  may adapt the multi-channel audio signal  142  so that an indirect component of the signal (echo) is reduced relative to a direct component of the signal. Likewise, if the conditioning block  740  determines that there is a particularly sound-reflective environment near to/behind the portable microphone  110  but not obstructing the path from the portable microphone  110  to the origin of the rendered sound scene, then the conditioning block  740  may increase the indirect component (echo) of the multi-channel audio signal  142  relative to the direct component. 
     The acoustic environment sensor  750  may also be configured to sense a real line-of-sight acoustic environment of the portable microphone  110  (sound object). The real line-of-sight acoustic environment of the portable microphone  110  relates to the likelihood of a sound recorded by the portable microphone  110  reaching the origin of the rendered sound scene directly. As the portable microphone  110  is associated with a sound object, in some examples it can be assumed that the portable microphone  110  and the sound object are co-located and therefore the real line-of-sight acoustic environment is the likelihood that sound from the sound object co-located with the portable microphone  110  can reach the origin of the rendered sound scene directly in a line-of-sight path. The acoustic environment sensor  750  is therefore configured to detect whether or not there is an obstruction in the acoustic environment between the portable microphone  110  (sound object) and the origin of the rendered sound scene, and, in some examples, if there is an obstruction, to sense the acoustic characteristics of the obstruction. This real line-of-sight acoustic environment may, for example, arise if an object passes between the origin of the rendered sound scene and the portable microphone  110 , if the portable microphone  110  moves behind an obstruction which may occur, for example, if a person wearing the portable microphone  110  moves behind an obstruction or if they turn so that their body forms an obstruction. The obstruction of the real line-of-sight acoustic environment, may be compensated for by the conditioning block  740  by increasing the indirect component (multi-path) of the multi-channel signals  142  relative to the direct component of the multi-channel audio signals  142 , while simultaneously reducing the amplitude/intensity of the multi-channel audio signals  142  associated with the portable microphone  110 . 
       FIG. 8  illustrates an example of a conditioning block  740  illustrated in  FIG. 7 . In this example, the conditioning block  740  is a module which may be used, to perform the functions of the conditioning block  740  in  FIG. 7 . The module  740  may be implemented using circuitry and/or programmed processors. 
     The figure illustrates the processing of a single channel of the multi-channel audio signal  142  before it is mixed with the multi-channel audio signal  132  to form the multi-microphone multi-channel audio signal  103 . A single input channel of the multi-channel signal  142  is input as signal  187 . 
     The input signal  187  passes in parallel through a “direct” path and one or more “indirect” paths before the outputs from the paths are mixed together, as multi-channel signals, by mixer  196  to produce the output multi-channel signal  197 . The output multi-channel signals  197 , for each of the input channels, are mixed to form the multi-channel audio signal  142  that is mixed with the multi-channel audio signal  132 . 
     The direct path represents audio signals that appear, to a listener at an origin of the rendered sound scene, to have been received directly from an audio source and an indirect path represents audio signals that appear to a listener, at an origin of the rendered sound scene, to have been received from an audio source via an indirect path such as a multi-path or a refracted path. 
     A controller block  760 , by modifying the absolute gain of the direct path, the absolute gain of the indirect path(s), the relative gain between the direct path and the indirect path(s), and the parameters of the indirect path(s) changes a perception of the sound object, represented by the portable microphone signals  112 , from a perspective of a listener at an origin of the rendered sound scene. 
     Each of the parallel paths comprises a variable gain device  181 ,  191  which is controlled by the controller block  760  via control signals  771 ,  772 . 
     The controller block  760  takes as its inputs the position  741  of the portable microphone  110  and sensor information  742  characterizing the acoustic environment of the portable microphone  110  from the acoustic environment sensor  750 . 
     The perception of intensity can be controlled by controlling the absolute gain of the direct path and/or the indirect (decorrelated) paths via control signals  771 ,  772 . The perception of a clear, unobstructed path between the portable microphone  110  (sound object) and the origin of the rendered sound scene can be increased by increasing the gain of the direct path relative to the indirect path(s). The perception of an obstruction between the portable microphone  110  (sound object) and the origin of the rendered sound scene may be provided by decreasing the absolute gain of the direct path and the indirect paths and also increasing the indirect path gain relative to the direct path gain via control signals  771 ,  772 . Alternatively or in addition, filtering such as low-pass filtering may be applied to simulate the attenuation of high frequencies when a sound passes through a wall, for example. The perception of an echo inducing environment in the vicinity of the portable microphone  110  may be controlled by controlling the relative gain between the direct path and the indirect paths, for example increasing the relative gain of the direct path via control signals  771 ,  772 . Alternatively or in addition, extra reverb effect may be applied to create a stronger reverberation effect. 
     In the direct path, the input signal  187  is amplified by variable gain device  181 , under the control of the control signal  771  from the controller block  760  to produce a gain-adjusted signal  183 . The gain-adjusted signal  183  is processed by a direct processing module  182  to produce a direct multi-channel audio signal  185 . 
     In each indirect path, the input signal  187  is amplified by a different variable gain device  191 , under the control of a different control signal  772  from the controller block  760 , to produce gain-adjusted signals  193 . The gain-adjusted signals  193  are processed by indirect processing modules  192  to produce indirect multi-channel audio signals  195 . 
     The direct multi-channel audio signal  185  and the one or more indirect multi-channel audio signals  195  are mixed in the mixer  196  to produce the output multi-channel signal  197 . 
     The direct processing block  182  and the indirect processing block  192  both receive a separate control signal  761 ,  762 . The control signal  761  provided to the direct processing block  182  corresponds to the signal  188  illustrated in  FIG. 4A . It may, for example, be a direction of arrival signal giving the orientation of the portable microphone  110  (moving sound object) in the recorded sound scene. The direct module  182  may, for example, include a module  184  similar to that illustrated in  FIG. 4A  that rotates the single channel audio signal, gain-adjusted input signal  183 , in the appropriate multi-channel space producing the direct multi-channel audio signal  185 . The module  184  uses a transfer function to perform a transformation T that rotates the multi-channel signals within the space, as previously described. 
     The indirect module  192  may, for example, be implemented as previously described in relation to  FIG. 4B . The control signal  762  provided by the controller module  760  corresponds to the signal  188  in  FIG. 4B  and controls the gain of the single channel audio signal, the gain-adjusted input signal  193 , using a variable gain device  194 . The amplified signal is then processed using a static decorrelator  199  and a module  198  then applies a static transformation T to produce the output multi-channel audio signal  195 . In this example, the static decorrelator uses a pre-delay of at least 2 milliseconds. 
     In some examples, it may be possible to have multiple different indirect paths each with a different indirect module  192 . Each separate indirect path may, for example, have a indirect module  192  that has a different static decorrelator, for example, a static decorrelator  199  with a different pre-delay. In some examples, the control signal(s)  762  may be used to control which of the indirect paths  192  are used and/or the relative gain of each of the indirect paths relative to each other. 
     It will therefore be appreciated that the controller module  760  can be used to process the portable microphone signals  112  and perform conditioning dependent upon the real audio environment. 
     It should also be appreciated, that when conditioning based upon the real audio environment is used, the controller  760  may, in addition, perform the function of the positioning block  140  and that when conditioning of the signal based upon the audio environment is not required, then the controller  760  performs the function of the positioning block  140 . 
     The controller  760  is able through the sensor information  742  to remotely sense a real acoustic environment in which multiple audio signals are captured. In some, but not necessarily all, examples the controller  760  is configured to map a sensed acoustic environment to a recorded sound scene comprising multiple sound objects to determine a relationship of the sensed acoustic environment to the multiple sound objects in the recorded sound scene from a perspective of an origin of a rendered sound scene. In this example, the controller module  760  receives a position  741  providing the position of the portable microphone  110 . The controller module  760  is able to determine the origin in the rendered sound scene, the position of the portable microphone  110  in the rendered sound scene and to determine via the sensor information  742  the real acoustic environment of the portable microphone  110 . The controller module  760  is configured to enable automatic control of mixing of the audio signal representing the sound object associated with the portable microphone  110  to condition that sound object for an effect of the sensed acoustic environment on the sound object from the perspective of the origin of the rendered sound scene. For example, as previously described, the controller module  760  is configured to control the absolute and relative gains of the direct and indirect paths of each channel of the portable microphone signals  112 . 
     The controller module  760  is also configured, based upon the sensor information  742 , to switch on and switch off conditioning of the portable microphone signals  112  based upon the real acoustic environment. If conditioning of the portable microphone signals  112  based upon the sensed acoustic environment is performed, then the controller module  760  controls the conditioning by, for example, controlling the absolute and relative gains of the direct and indirect paths of each channel of the portable microphone signals  112 . It will be appreciated that the controller module  760  is able to adapt the conditioning of the portable microphone signals  112  based upon adaptations to the acoustic environment determined by the acoustic environment sensor  750  provided to it by the sensor information  742 . In this way, variations over time of the real acoustic environment in the recorded sound scene also result in changes in the rendered sound scene. In some, but not necessarily all, examples if there is a sudden change to the real acoustic environment then the controller module  760  may apply an adaptation to the conditioning of the portable microphone signals  112  more gradually so that there is not a sudden change in the audio characteristics of the rendered sound scene. However, this gradual adaptation may be a controllable parameter which may be adjusted by a user so that in other circumstances abrupt transition may occur in the audio characteristics of the rendered sound scene. 
     The acoustic environment sensor  750  is a sensor that tests the acoustic environment of the portable microphone  110  (sound object). The testing of an acoustic environment may typically involve the transmission of a sensing signal and the reception of a response signal. The response signal may be, for example, a version of the sensing signal that has been adapted by the acoustic environment by for example, transmission through the real acoustic environment or reflection from the real acoustic environment. The acoustic environment may therefore be considered to be a transfer function that operates upon the sensing signal to produce the response signal. The selection of the characteristics of the sensing signal, where it is transmitted from, and where the response signal is detected are design considerations that may be varied. 
     In the examples of  FIGS. 9A, 9B, 10A, 10B and 11A, 11B  a video camera  900  is positioned at an origin O of a rendered sound scene. The video camera  900  images the recorded sound scene and, in particular, the person wearing the portable microphone  110 . It is important that there is no incongruity between the rendered audio sound scene and the visual scene recorded by the camera. As the portable microphone  110  is local to the sound object carrying the portable microphone the sound object as recorded by the portable microphone  110  does not necessarily represent the sound object as should be perceived at the origin O of the rendered sound scene. For example, if an obstruction  910  passes between the portable microphone  110  and the origin O of the rendered sound scene at the camera  900  then the obstruction  910  will have an impact on the visual scene as recorded by the camera  900  and should therefore also have a consequential impact on the rendered sound scene at the origin O. The conditioning block  740  as previously described causes this change in the rendered sound scene as perceived from the origin O of the rendered sound scene. 
     In each of the examples, an active transmitter device transmits a sensing signal  902  and a receiver device receives a response signal  904  based upon the impact of the acoustic environment on the sensing signal  902 . 
     In the example of  FIGS. 9A and 9B , the camera  900  is the transmitter device transmitting the sensing signal  902  which is reflected by the acoustic environment (or not) as the response signal  904  which is then detected by the receiver device, also at the camera  900 . In the example of  FIG. 9A , there is no audio obstruction between the camera  900  and the portable microphone  110 . In this example, there may be no or little response signal  904  from the acoustic environment. In other examples, where the real ambient acoustic environment is particularly reflective, there may be a response signal  904  detected by the camera  900 . In the example of  FIG. 9B , an audio obstruction  910  intervenes in the path between the camera  900  and the portable microphone  110 . In this example there is a strong reflection of the sensing signal  902  from the audio obstruction  910  to produce the response signal  904  detected at the camera  900 . It will be appreciated that the timing of the response signal  904  relative to the sensing signal  902  and the intensity of the response signal  904  relative to the sensing signal  902  is different in  FIG. 9B  than it is in  FIG. 9A . This timing and intensity information may be used as the sensing information  742 . It is therefore possible for the conditioning module  740  to detect a change in the real acoustic environment of the portable microphone  110  and to adapt the conditioning of the portable microphone signals  112  as previously described. 
     In the example of  FIGS. 10A and 10B , the camera  900  is the transmitter device transmitting the sensing signal  902  and the portable microphone  110  is the receiver device receiving the response signal  904  which is the sensing signal  902  after it has passed through the acoustic environment in the line-of-sight between the camera  900  and the portable microphone  110 . The portable microphone  110 , in this example, is configured to transmit a reply signal  920  to the camera  900 , for example using radio waves or some other communication technology that will not be affected by an acoustic obstruction  910  in the line-of-sight between the camera  900  and the portable microphone  110 . In the example of  FIG. 10A , while there is no acoustic obstruction  910 , the sensing signal  902  is transmitted by the camera  900  and is received, without significant interference, as the response signal  904  at the portable microphone  110 . The portable microphone  110 , in this example, is able to receive the response signal  904  and provide information concerning the response signal  904  to the camera  900  via the reply signal  920 . The camera  900  is therefore able to use information concerning the sensing signal  902  transmitted by it and the response signal  904  received at the portable microphone  110  to create the sensing information  742 . In the example of  FIG. 10A  the signals  902 , 904  will be very similar. However, in the example of  FIG. 10B , an acoustic obstruction  910  is placed between the camera  900  and the portable microphone  110  and prevents all or some of the sensing signal  902  reaching the portable microphone  110  as the response signal  904 . The reply signal  920  provided by the portable microphone  110  in  FIG. 10B  is therefore very different to the reply signal  920  provided in the example of  FIG. 10A . The camera  900  receives the adapted reply signal  920  as sensing information  742  and the conditioning block  740  conditions the portable microphone signal  112  accordingly. 
     In the example of  FIGS. 11A and 11B , the system is similar to that illustrated in  FIGS. 10A and 10B  except that the transmitter of the sensing signal  902  is the portable microphone  110  and the receiver of the response signal  904  is the camera  900 . The sensing signal  902  is adapted by the acoustic environment between the portable microphone  110  and the camera  900  to produce the response signal  904 . In the example of  FIG. 11A , the received response signal  904  has characteristics similar to transmitted sensing signal  902  and the camera  900  is therefore able to determine that there is no acoustic obstruction in the line-of-sight between the portable microphone  110  and the camera  900 . In the example of  FIG. 11B , acoustic obstruction  910  completely or partially blocks the sensing signal  902  so that only a reduced or no response signal  904  is received at the camera  900 . The reduced response signal  904  or the absence of a response signal  904  may be used as sensing information  742 . In this example the conditioning block  740  responds to the reduced/absent response signal  904  by changing the conditioning applied to the portable microphone signal  112 . 
     It will be appreciated from the embodiments of  FIGS. 9 to 11 , that in each of these embodiments the remote sensing of a real acoustic environment in which multiple audio signals are captured, comprises receiving a remote sensing signal dependent upon the real acoustic environment in which the multiple audio signals are captured. In the examples of  FIGS. 9A and 9B , the remote sensing signal is the response signal  904 . In the examples of  FIGS. 10A and 10B  the remote sensing signal is the reply signal  920 . In the example of  FIGS. 11A and 11B  the remote sensing signal is the response signal  904 . 
     It should be appreciated that in both of the examples of  FIGS. 9 and 10 , remotely sensing a real acoustic environment in which multiple audio signals are captured, comprises transmitting a sensor signal (sensing signal  902 ) and detecting a consequent signal as the remote sensing signal. In the example of  FIG. 9 , the consequent signal is a response signal  904 , i.e. the reflected sensing signal  902 . In the example of  FIGS. 10A and 10B , the consequent signal is the reply signal  920  transmitted by the portable microphone  110 . 
     In both the examples of  FIGS. 10 and 11 , the remote sensing signal is a signal transmitted by a sound object. In the example of  FIGS. 10A and 10B , the remote sensing signal is the reply signal  920  transmitted by the portable microphone  110  and in the example of  FIGS. 11A and 11B  the remote sensing signal is the sensing signal  902  transmitted by the portable microphone  110 . 
     It will be appreciated from the foregoing that in the example of  FIGS. 9A and 9B  the portable microphone  110  is passive concerning the sensing of the audio environment. The camera  900  transmits the sensing signals  902  which are passively reflected by the acoustic environment and the reflected signals are detected as the response signal  904  by the camera  900 . The portable microphone  110  is therefore passive and not involved at all in sensing the audio environment. 
     In the examples of  FIGS. 10 and 11 , the portable microphone  110  is active in the sensing of the acoustic environment. In the example of  FIGS. 10A and 10B , the portable microphone  110  receives the response signal  904  and transmits the reply signal  920  and in the examples of  FIGS. 11A and 11B  the portable microphone  110  produces the sensing signal  902 . 
     In the preceding examples, the sensing signal  902  may be, for example, a radar signal, a lidar signal, for example infrared light, or a sonar system using sound outside the hearing range of humans. It will be appreciated from  FIGS. 9B, 10B and 11B , that the sensing signal  902  may be used to detect the presence of a wall  910  between a user wearing a Lavalier microphone  110  and the camera  900 . 
     Referring now to the examples of  FIGS. 9A and 9B , the camera  900  may produce the sensing signal  902  as a directed, limited spread transmission and the acoustic environment sensor  750  may be configured to control a direction of transmission of the transmitted sensor signal (sensing signal  902 ) in dependence upon a position of the sound source (portable microphone  110 ). In this example the conditioning module  740  may use the position  741  of the portable microphone  110  to control the acoustic environment sensor  750  and a control signal will be sent from the conditioning module  740  to the acoustic environment sensor  750 . In some examples, it may be for example possible for the sensing signal  902  to track the portable microphone  110  so that the acoustic environment sensor  750  receives only information concerning the line-of-sight acoustic environment between the camera  900  and the portable microphone  110 . It will be appreciated that there are advantages to having a directed, narrow beam sensing signal  902  as it will not therefore be subject to interference outside the line-of-sight between the camera  900  and the portable microphone  110 . 
     In a variation of the example illustrated in  FIGS. 9A and 9B , the acoustic environment sensor  750  may be configured to project over a greater area, different spatially distinct sensing signals  902  simultaneously. The different spatially distinct signals are projected into the real acoustic environment and the acoustic environment sensor  750  detects the reflections. In some examples, if the different spatially distinct sensing signals  902  have characteristics that are also detectable in the reflected signals, it is possible to distinguish between different audio characteristics of different parts of the real acoustic environment. It may therefore be possible to record the real acoustic environment as a two-dimensional map that has different audio characteristics at different locations (different bearings). 
     In some examples, it may be possible to have a diversity receiver at the acoustic environment sensor  750  that receives a reflected sensing signal  902  as the response signal  904  at different, diverse, receiver locations. This additional information may be, for example, used to not only identify an audio characteristic of a portion of the real audio environment but also to estimate a distance of that portion of the real audio environment from the origin of the rendered scene. It is therefore possible, in this scenario, to create an audio depth map that maps the real audio environment in relation to its audio characteristics and the spatial variations of those audio characteristics as a three-dimensional map of the audio environment that has different audio characteristics at different three-dimensional locations. This sensing information  742  may be particularly useful to create additional effects such as echoes which are distance-dependent. This sensing information  742  may also be useful if the acoustic environment sensor  750  is not co-located with the camera  900 . The sensing information  742  is output from the acoustic environment sensor  750  to the conditioning module  740  which uses this information to control the conditioning of the portable microphone signal  112 . 
     In the examples of  FIGS. 9 to 11 , audio obstruction  910  may fully or partially obstruct the line-of-sight between the camera  900  and the portable microphone  110 . As previously described in relation to those figures, it is possible for the acoustic environment sensor  750  or conditioning module  740  to discriminate between a full obstruction of the line-of-sight and a partial obstruction. The conditioning module  740  may, in the examples of  FIGS. 9A, 10A and 11A , operate as the positioning module  140  of  FIG. 1  and in the examples of  FIGS. 9B, 10B and 11B , additionally operate to control the conditioning of the portable microphone signals  112  to take account of the different acoustic environment and, in particular, the presence of a full or partial obstruction of the direct line-of-sight acoustic path from the portable microphone  110  to the camera  900 . The conditioning module  740  may, for example, be able to condition the portable microphone signals  112  in dependence upon the presence of an audio obstruction and/or in dependence upon the audio characteristics of the audio obstruction  910  by, for example, adjusting the absolute gains of the direct path component and the indirect path components and/or the relative gain of the direct path component and indirect paths component and/or by adapting the characteristics of the indirect paths as previously described in relation to  FIG. 8 . The characteristics of an audio obstruction may, for example, include its density and/or its size. 
       FIG. 12  illustrates an example of a rendering device  1000  which receives the multi-microphone multi-channel audio signal  103  produced by the system  100  illustrated in  FIG. 7  and video  1001  provided by the camera  900  as illustrated in any of  FIGS. 9-11 . The rendering device  1000  synchronizes the audio  103  and the video  1001  to produce a multi-media output  1002  in which the video and audio are synchronized. In addition, as a result of the conditioning module  740  in the system  100  of  FIG. 7 , if an acoustic obstruction  910  moves between the camera  900  and the portable microphone  110 , there is an automatic change to not only the image as recorded by the camera  900  as the obstruction passes between the camera  900  and the portable microphone  110  but there is also an automatic change in the rendered sound scene that has an origin at the camera  900  as a consequence of the processing of the conditioning block  740  of  FIG. 7  and the method  500  of  FIG. 6 . 
       FIG. 5  illustrates an example of the system  100 , comprising conditioning block  740  as illustrated in  FIG. 7 , implemented using an apparatus  400 , for example, a portable electronic device. 
     It will be appreciated from the foregoing that the various methods  500  described may be performed by a computer program used by such an apparatus  400 . 
     For example, an apparatus  400  may comprise: 
     at least one processor  412 ; and
 
at least one memory  414  including computer program code
 
the at least one memory  414  and the computer program code configured to, with the at least one processor  412 , cause the apparatus  400  at least to perform:
 
enabling automatic control of mixing of multiple captured audio signals based on remote sensing of a real acoustic environment in which the multiple audio signals were captured.
 
     References to ‘computer-readable storage medium’, ‘computer program product’, ‘tangibly embodied computer program’ etc. or a ‘controller’, ‘computer’, ‘processor’ etc. should be understood to encompass not only computers having different architectures such as single/multi-processor architectures and sequential (Von Neumann)/parallel architectures but also specialized circuits such as field-programmable gate arrays (FPGA), application specific circuits (ASIC), signal processing devices and other processing circuitry. References to computer program, instructions, code etc. should be understood to encompass software for a programmable processor or firmware such as, for example, the programmable content of a hardware device whether instructions for a processor, or configuration settings for a fixed-function device, gate array or programmable logic device etc. 
     As used in this application, the term ‘circuitry’ refers to all of the following: 
     (a) hardware-only circuit implementations (such as implementations in only analog and/or digital circuitry) and
 
(b) to combinations of circuits and software (and/or firmware), such as (as applicable): (i) to a combination of processor(s) or (ii) to portions of processor(s)/software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions and
 
(c) to circuits, such as a microprocessor(s) or a portion of a microprocessor(s), that require software or firmware for operation, even if the software or firmware is not physically present. This definition of ‘circuitry’ applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term “circuitry” would also cover an implementation of merely a processor (or multiple processors) or portion of a processor and its (or their) accompanying software and/or firmware. The term “circuitry” would also cover, for example and if applicable to the particular claim element, a baseband integrated circuit or applications processor integrated circuit for a mobile phone or a similar integrated circuit in a server, a cellular network device, or other network device.
 
     The blocks and methods illustrated in or described in relation to one or more of the  FIGS. 1-12  may represent steps in a method and/or sections of code in the computer program  416 . The illustration of a particular order to the blocks does not necessarily imply that there is a required or preferred order for the blocks and the order and arrangement of the block may be varied. Furthermore, it may be possible for some blocks to be omitted. 
     Where a structural feature has been described, it may be replaced by means for performing one or more of the functions of the structural feature whether that function or those functions are explicitly or implicitly described. 
     As used here ‘module’ refers to a unit or apparatus that excludes certain parts/components that would be added by an end manufacturer or a user. 
     The term ‘comprise’ is used in this document with an inclusive not an exclusive meaning. That is any reference to X comprising Y indicates that X may comprise only one Y or may comprise more than one Y. If it is intended to use ‘comprise’ with an exclusive meaning then it will be made clear in the context by referring to “comprising only one . . . ” or by using “consisting”. 
     In this brief description, reference has been made to various examples. The description of features or functions in relation to an example indicates that those features or functions are present in that example. The use of the term ‘example’ or ‘for example’ or ‘may’ in the text denotes, whether explicitly stated or not, that such features or functions are present in at least the described example, whether described as an example or not, and that they can be, but are not necessarily, present in some of or all other examples. Thus ‘example’, ‘for example’ or ‘may’ refers to a particular instance in a class of examples. A property of the instance can be a property of only that instance or a property of the class or a property of a sub-class of the class that includes some but not all of the instances in the class. It is therefore implicitly disclosed that a features described with reference to one example but not with reference to another example, can where possible be used in that other example but does not necessarily have to be used in that other example. 
     The term ‘capture’ or ‘record’ in relation to an audio signal describes the transformation of sound waves to an electrical signal by a microphone. It may in addition also describe the temporary or permanent storage of data representing the captured audio in a lossless or lossy format. 
     Although embodiments of the present invention have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the invention as claimed. 
     Features described in the preceding description may be used in combinations other than the combinations explicitly described. 
     Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not. 
     Although features have been described with reference to certain embodiments, those features may also be present in other embodiments whether described or not. 
     Whilst endeavoring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.