GB2617579A - Receiving sound from a plurality of participants - Google Patents

Abstract

The conferencing microphone apparatus (fig 2) is located at a position for being substantially surrounded by the participants and audio output signals are provided from a USB output interface 107. A plurality of microphone capsules 101, 102, 104, 105 are provided, wherein each includes a receptive face that is most receptive to sound waves approaching substantially normally. A processing system 106 processes audio input signals from the microphone capsules and supplies audio output signals to the USB output interface. The housing comprises a plurality of grilles (201,202, fig 2) and the receptive face of each said microphone capsule is aligned behind a respective housing grille. Each grille and the respective face of its aligned microphone capsule is inclined with respect to a horizontal plane and the grilles are mutually displaced around a vertical axis 103. An operator manual control and display interface may be located on the top surface of the apparatus (204, fig 2).

Description

Receiving Sound from a Plurality of Participants

CROSS REFERENCE TO RELATED APPLICATIONS

This is the first application for a patent directed towards the invention and the subject matter.

TECHNICAL FIELD

The present invention relates to an apparatus for receiving sound from a plurality of participants. The present invention also relates to a method of receiving sound from a plurality of participants.

BACKGROUND OF THE INVENTION

Microphones for receiving audio signals from a plurality of participants are known. In some situations, an individual microphone may be provided for each participant and this may be identified as an ideal solution. However, such an approach can be cumbersome if the participants are not using a purpose-built environment. In a non-purpose-built environment, mobile systems may be deployed but often this may involve moving an apparatus when a particular participant is speaking. However, if several participants are to be received at the same time, problems occur which in turn may lead to a degradation of the received audio signals and a consequent difficulty in terms of hearing or recording all of the participants due to the quality of the signals received.

BRIEF SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provided an apparatus for receiving sound from a plurality of participants, as set out in claim 1.

According to a second aspect of the present invention, there is provided a method of receiving sound from a plurality of participants, as set out in claim 16.

Embodiments of the invention will be described, by way of example only, with reference to the accompanying drawings. The detailed embodiments show the best mode known to the inventor and provide support for the invention as claimed. However, they are only exemplary and should not be used to interpret or limit the scope of the claims. Their purpose is to provide a teaching to those skilled in the art. Components and processes distinguished by ordinal phrases such as "first" and "second" do not necessarily define an order or ranking of any sort.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Figure 1 shows an apparatus for receiving sound from a plurality of participants; Figure 2 shoes grilles extending from the housing of the microphone identified in Figure 1; Figure 3 illustrates a cardioid response; Figure 4 shows a processing system included in the microphone identified in Figure 1; Figure 5 shows the apparatus connected to a USB cable; Figure 6 illustrates the application of manual pressure upon the apparatus; Figure 7 illustrates the muting of the apparatus; Figure 8 illustrates modes of operation; Figure 9 shows a functional schematic representation of operations performed by the processing system identified in Figure 4; Figure 10 illustrates a group mode of operation; Figure 11 shows the processing system of Figure 4 configured in response to the solo sub mode being selected; Figure 12 shows the processing system of Figure 4, configured to operate in the vocal sub mode; Figure 13 shows the processing system of Figure 4 configured for the music sub mode; Figure 14 shows the processing system of Figure 4 modified to operate in the immersive mode; Figure 15 shows frequency responses for the equalisers shown in Figure 10; and Figure 16 details a method of operating the apparatus.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Figure 1 An apparatus for receiving sound from a plurality of participants is shown in Figure 1. The apparatus includes a plurality of microphone capsules, including a first capsule 101 and a second capsule 102. Each capsule is housed behind a protective grille, wherein these grilles are regularly displaced around a central vertical axis 103.

Embodiments are likely to have less than nine grilles of this type and the embodiment of Figure 1 has four grilles mutually displaced by ninety degrees around the central vertical axis 103. Thus, the embodiment of Figure 1 includes a third microphone capsule at a location indicated by arrow 104 and a fourth microphone capsule at a position indicated by arrow 105. The grilles are further described with reference to Figure 2.

Each microphone capsule 101, 102 etc includes a receptive face that is most receptive to soundwaves approaching in a substantially normal direction, as described further with reference to Figure 3.

A processing system, described further with reference to Figures 4 to 6, is mounted on a circuit board 106 and is configured to process audio input signals received from the microphone capsules to supply audio output signals to an output interface; with the embodiment of Figure 1 presenting a micro-USB interface 107. In an embodiment, input signals are also returned to the USB interface 107.

Each grille, detailed with reference to Figure 2, and the respective face of its aligned microphone capsule (101, 102) is inclined with respect to a horizontal plane, with the grilles being mutually displaced around the central vertical axis 103.

The embodiment of Figure 1 includes a silicone rubber base 108 and may also include a tapped hole compatible with photographic tripods etc. A rigid microphone frame 109 supports respective slings of an elastomeric material, including a first sling 110, for each capsule, to provide mechanical decoupling.

A top portion 111 includes a second circuit board for supporting a touch sensitive light emitting screen, covered by an acrylic light diffuser, and a polycarbonate top that may carry visual indications to a user and possibly a logo-type graphic.

In an embodiment, the microphone capsules have a diameter of 9.5 mm and suitable devices are available from Kingstate Electronic Corporation of Taiwan.

Figure 2 The housing for the microphone includes a plurality of protective grilles, including a first grille 201 and a second grille 202. Compared to the orientation shown in Figure 1, the base 108 has been rotated through one hundred and eighty degrees around the central vertical axis 103, such that the third microphone capsule 104 is behind the first grille 201 and the fourth microphone capsule 105 is behind the second grille 202. The first grille 201 includes a cutaway 205 behind which is a socket 206 for receiving a headphone plug.

Each housing grille 201, 202, along with a third obscured grille 203 and a fourth obscured grille 204, are inclined with respect to a horizontal plane. In an embodiment, the angle of inclination 207 is greater than thirty degrees and may be less than sixty degrees. In the embodiment of Figure 2, each housing grille is inclined with respect to the horizontal plane by an angle of substantially forty-five degrees.

In the embodiment of Figure 2, the inclined housing grilles extend from the substantially flat base 108 that defines a regular shape, to the smaller top portion 111 of the same regular shape. Thus, in the embodiment of Figure 2, these regular shapes are square, given that the embodiment presents four inclined grilles. However, it can be appreciated that other shapes are possible, with five grilles presenting a pentagon and six grilles presenting a hexagon etc. The substantially flat top portion 111 includes manually receptive input devices for supplying control data to the processing system, along with visual indicating devices to display output data from the processing system. The input devices include a first manually responsive input device 211, showing a minus sign, along with a second input device 212 showing a plus sign, primarily for adjusting volume levels. The volume level of an output signal supplied to connected headphones is indicated by a first output indicator 221 and a colour changing display 222 indicates modes of operation. The colour changing display 222 is also responsive to manual input.

Figure 3 In an embodiment, the microphone capsules 101, 102 etc have a substantially cardioid response as illustrated in Figure 3. The first microphone capsule 101 is shown schematically in Figure 3, having a receptive face 301 that aligns with its respective grille 203. The receptive face 301 is most receptive to sound waves approaching the face substantially normally, as indicated by arrow 302.

A polar pattern 303 is shown, indicating the sensitivity of the microphone capsule to sounds arriving from different directions. The cardioid polar pattern shows the highest sensitivity to sound coming in from directly in front of the microphone (zero degrees) with practically no sensitivity to sound coming from directly behind (at one hundred and eighty degrees) and reduced sensitivity to sound coming in from the sides (ninety degrees/two hundred and seventy degrees). In this way, the microphones are most sensitive to receiving speech from users positioned directly in front of a respective inclined surface, with the inclined angle improving the preferred directional axis, as indicated by arrow 302.

With users arranged around the microphone, different utterances are received by the respective microphones, thereby facilitating a mixing operation which allows the users to be separated in an audio field by the production of an appropriately mixed stereo signal. Alternatively, if preferred, all four signals can be supplied separately to a recording or telephonic device; typically, a laptop computer.

Figure 4 A processing system 401 is shown in Figure 4 for processing audio signals from the microphone capsules, to supply audio output signals to the output interface 107. The processing system 401 may be implemented substantially around an XU212 processor produced by Xmos Limited of the United Kingdom, containing multiple processing cores and memory for storing executable instructions.

Although the apparatus is primarily concerned with receiving sound from a plurality of participants, an embodiment may also be configured to receive sound from a single participant, with the normal mode being identified as a group mode whereas the alternative, when receiving sound from a single participant, is identified as a solo mode. When operating in the solo mode, the single participant should be aligned with the first inclined grille 201, indicated by the location of the headphone socket 204; given that the single participant is likely to be wearing headphones. Consequently, microphone 104 is identified as the front, with microphone 102 identified as the right, microphone 105 identified as the left and microphone 101 identified as the back; arranged in Figure 4 As 105L, 102R, 104F and 101B.

The processing system 401 receives four input signals from respective microphone capsules via a respective microphone preamplifier, a soft clipping circuit and an analogue to digital converter. Thus, the output from the first microphone capsule 101B is supplied to a first preamplifier 411, a first soft clipping circuit 421 and a first analogue to digital converter 431, with similar devices being provided for the other three inputs.

In an embodiment, the analogue to digital converters (431, 432, 433 and 434) are implemented using devices supplied by Texas Instruments, with each individual device accepting two analogue inputs such that two physical devices of this type are required. The microphone preamplifiers (411, 412, 413, 414) ensure that the analogue signals are optimised with respect to the sensitivity of the respective analogue to digital converters 431 to 434. The respective soft clipping stages 431 to 434 prevent the analogue to digital converters 431 to 434 from overloading.

Amplifier gains for the preamplifiers 411 to 414 are controlled by the processing system 401, again ensuring, in combination with the soft clipping circuits, that the analogue to digital converters do not receive an overvoltage which would introduce undesirable distortion. A control line 415 supplies control signals from the processing system 401 to amplifiers 411 to 414 and this varies depending upon the mode of operation, described with reference to Figures 8 to 15.

Output signals are supplied to an external device via a USB cable 441. The external device may be an audio recorder, a video recorder, an amplifier, a public address system, a telecommunications system or a computer. The external device indicated at 442 and may, for example, be implemented as a laptop computer.

The USB interface 107 receives a stereo output signal and provides a left channel 443L and a right channel 443R. In addition, the USB interface 107 may receive individual outputs from the individual microphone capsules shown as 444L, 444R, 444F and 444B.

The USB interface 107 is also configured to receive input signals from the external device 442, which again may be in the form of a stereo pair implemented as a left signal 445L and a right signal 445R. These are supplied to the headphone socket 204 via a first digital to analogue converter 446L and a second digital to analogue converter 446R.

Figure 5 The apparatus receives power from the external device 442 over the USB cable 441. To activate the device, a USB plug 501 is inserted into the USB interface 107. Upon receiving power, the colour changing display 222 is illuminated and displays a colour representing the mode being used when the apparatus was previously deactivated.

Usually, when receiving audio from a plurality of participants, the microphone is placed substantially centrally, thereby allowing it to pick up speech from all of the participants present without being required to be moved again.

Figure 6 As shown in Figure 6, the colour changing display 222 is responsive to manually applied pressure. When operating in a selected mode, the colour changing display 222 will display a solid green, white, magenta or cyan colour when operating in a stereo mode. The display will flash between one of these colours and yellow when operating in an immersive mode. By pressing the colour changing display as shown in Figure 6, the microphones are muted and the display will show a red colour.

Headphones may be plugged into the headphone socket 206. The volume of signals supplied to the headphones may be adjusted by applying pressure to the first manually responsive input device 211 to reduce the volume or pressure may be applied to the second manually responsive input device 212 to increase the volume of signals supplied to the headphones. In addition to increasing or decreasing the audio level, the first output indicator 221 reflects this by changing brightness, becoming brighter when a louder signal is being supplied and less bright when the volume level is reduced. The first output indicator 221 will also display a solid red colour if the second manually responsive input device is operated repeatedly such that the volume level is reduced to zero.

Figure 7 By simultaneously pressing the first manually responsive input device 211 and the second manually responsive input device 212, as shown in Figure 7, for more than two seconds, it is possible to select a set up mode. In the set up mode, pressing the colour changing display 222, as described with reference to Figure 6, allows sub modes to be selected in both the stereo mode and the immersive mode.

Switching between the stereo mode and the immersive mode is achieved by pressing the colour changing display 222 for more than five seconds, while in the set up mode. If nothing is pressed for more than twenty seconds, the apparatus will return to the normal mode.

Figure 8 Modes of operation are illustrated in Figure 8. The muting possibility, described with reference to Figure 6, is illustrated at 801. When not muted, the colour changing display 222 displays an operational colour of green, white, magenta or cyan but after performing the operation described with reference to Figure 7, entering a mute condition, the display becomes red, thereby confirming to the participants that the microphone has been muted.

As described with reference to Figure 6, maintaining pressure on the colour changing display 222 for more than five seconds, when in the set up mode, results in switching between the stereo mode 802 and the immersive mode 803. When in the stereo mode 802, manual pressure applied to the colour changing display 222, when in the set up mode, causes sub modes (or operational modes) to cycle between a group sub mode 802G, a solo sub mode 802S, a vocal sub mode 802V and a music sub mode 802M.

When in the group sub mode 802G, the display 222 will flash between green and black and a further tap will select the solo sub mode 802S. In the solo sub mode 802S, the display 222 will flash between white and black. A Further application of pressure upon the display 222 will select the vocal sub mode 802V and the display 222 will flash between magenta and black. Again, the application of pressure upon the display 222 for less than two seconds will select the music sub mode 802M and the display will flash between cyan and black. A similar operation will then return the selected sub mode to the group sub mode 802G. Thus, sub mode selection cycles, allowing a participant to select the required mode of operation.

For a group of participants in conversation, the group sub mode 802G is most appropriate. After selection, manual pressure is again applied to both the first manually responsive input device 211 and the second manually responsive input device 212 to return the apparatus to its operational mode, during which a solid (non-flashing) colour will be displayed on the colour changing display 222; solid green for the group sub mode.

In the stereo mode, stereo signals are received, after a mixing operation, via the left channel 443L and the right channel 443R.

When pressure is applied upon the colour changing display 222 for more than five seconds, when in the set up mode, the immersive mode is selected, from which similar sub modes may be selected as 803G for group, 803S for solo, 803V for vocal and 803M for music. The sub modes, in the immersive mode, are substantially similar to those described with respect to the stereo mode 802, but instead of flashing between green and black for the group sub mode, the display flashes between green and yellow. Similarly, for the solo sub mode, flashing occurs between white and yellow (not white and black) and for the vocal sub mode flashing occurs between magenta and yellow. Similarly, for the music sub mode, flashing occurs between cyan and yellow instead of flashing between cyan and black.

As previously described, short applications of pressure upon display 222 causes the sub mode selection to cycle until the desired sub mode has been selected. When pressure is maintained for more than five seconds, mode selection returns to the stereo mode. Applying pressure to both devices 211 and 212 returns the apparatus to its operational mode. Alternatively, if nothing is pressed for more than twenty seconds, the apparatus will return to this operational (normal) mode.

Figure 9 A functional schematic representation of operations performed by the processing system 401 is shown in Figure 9. The system includes a first set of switches 901 and a second set of switches 902. As shown in Figure 9, these switches are usually closed when the system is operational but have been opened in response to a mute condition being selected, as described with reference to Figure 8.

Figure 10 The group sub mode of operation of the stereo mode is shown in Figure 10, with the mute switches 901 and 902 closed. Similarly, mute switches 901 and 902 are shown closed for the solo sub mode of operation, described with respect to Figure 11, the vocal sub mode of operation described with reference to Figure 12, the music sub mode of operation described with reference to Figure 13 and the immersive sub mode of operation described with respect to Figure 14.

In all operational modes, digital input signals are received from the analogue to digital converters 431 to 434. The input signals are initially processed by respective equalisers 1001, 1002, 1003 and 1004. A first type of equalisation is provided when in the group sub mode and when in the solo sub mode, whereas a second type of equalisation is performed when in the vocal sub mode or the music sub mode; further details of which will be described with reference to Figure 15.

An output signal is provided on control line 415 for controlling the preamplifiers 411 to 414. During the group, solo and vocal sub modes, a maximum sound pressure level of 104 dB is permitted. In the music mode, a maximum sound pressure level of 120 dB is permitted, under the control of line 415.

First signal paths 1011 connect the outputs from the equalisers 1001 to 1004 to the stereo output 443. Second signal paths 1012 connect the outputs from the equalisers 1001 to 1004 to the four immersive outputs 444. In the stereo mode 802, the immersive outputs are not required and switches in a third set of switches 1013 are open, as shown in Figure 10 (and also in Figures 11 to 13).

The system includes a fourth switch 1014, a fifth pair of switches 1015 and a sixth pair of switches 1016. In the group sub mode, the fourth switch 1014 is in an up position to receive an output from an auto mixer 1017, which in turn receives all four outputs from the respective equalisers 1001 to 1004. The fifth pair of switches 1015 are in an up position to provide stereo signals to respective gates 1017L and 1017R. If the gates 1017L/1017R receive signals that are below a predetermined threshold, the gates close such that the signal is totally blocked and no signal appears at the output. This gating is performed on the assumption that signals below the predetermined level are only derived from background noise, therefore this background noise is effectively blocked.

In an embodiment, the gate is used for the group sub-mode (green) and the solo sub-mode (white). The gate is set with an on threshold of -42dB, an off threshold of -48dB, a 4.5dB attenuation, a 5ms attack, a 100ms hold and a 200ms release.

The sixth pair of switches 1616 are also in an up position resulting in the outputs from the gates 1017L/1017R being supplied to a stereo compressing circuit 1018. For each channel, circuit 1018 includes a compressor 1019L/1019R followed by a makeup gain amplifier 1020L/1020R. The compressor 1019 attenuates high signal levels. The makeup gain amplifier then amplifies all of the signals; which is most noticeable in terms of amplifying the low-level signals. Thus, low-level signals appear louder and high-level signals appear quieter, with the overall dynamic range being compressed.

In an embodiment, the compressor is set in the group sub-mode with a threshold of -12dB, a ratio of 4:1, a knee of 12dB and attack of 5ms and a release of 100ms.

Figure 11 The processing system 401 is shown in Figure 11, configured in response to the solo sub-mode 802S being selected. This results in the fourth switch 1014 being placed in the lower position, such that only input 432 from the microphone at the front is processed through the first signal paths. The control signal on control line 415 remains the same, allowing a sound pressure level maximum of 104 dB and no modifications are made to the second equaliser 1002. However, in an embodiment, the compressing circuit 1018 has a threshold of -22dB, a ratio of 4:1, a knee at 22dB, an attack of 5ms and a release of 60ms. A stereo signal is then made available at the stereo output 443.

During the solo mode, it is likely that the single user will be wearing headphones. A loopback signal is derived from outputs 443 and supplied to respective amplifiers, comprising a first amplifier 1101 and a second amplifier 1102, to control the level of loopback. Return signals from the external device 442 received at 445 (consisting of a left signal 445L and a right signal 445R) are combined with the loopback signals in a first combiner 1111 and a second combiner 1112. Volume to the headphones is then controlled by a third amplifier 1123 and a fourth amplifier 1124 which are in turn supplied to the digital to analogue converters 446L and 446R.

Figure 12 The processing system 401 is shown in Figure 12, configured to operate in the vocal sub mode 802V. Inputs 431 to 434 are received from all four microphones and a stereo output is produced at 443. Thus, the signals are again processed through the first signal paths 1011. However, on this occasion, the fifth pair of switches 1015 have been placed in the lower position. This effectively disables the auto mixer 1017 and makes use of a seventh amplifier 1207 and an eighth amplifier 1208, along with a third combiner 1213 and a fourth combiner 1214.

The output from the front microphone 4321 is amplified by the seventh amplifier 1207 and the output from the microphone at the rear 431 is amplified by the eighth amplifier 1208. The third combiner and the fourth combiner combine signals from the left microphone 434 and the right microphone 433 to produce mixes that are then supplied to the compressing circuit 1018.

In an embodiment the compressing circuit deploys sidechain compression for sibilance reduction. The threshold is set at -28dB, with a ratio of 1.7:1 (introducing far less compression of the dynamic range) with a knee at 28dB, an attack of 5ms and a release of 100ms.

The output on control line 415 remains the same but the characteristics of the equalisers 1001 to 1004 are changed, as described with reference to Figure 15.

The vocal sub-mode 802V modifies the characteristics of the microphone such that they are more sympathetic to a singing voice compared to a talking voice. In this way, a device primarily intended for receiving speech can also be deployed in a more creative environment.

It is also appreciated that in the vocal mode and in the music mode (described with reference to Figure 13) relatively quiet passages may be present, therefore the sixth pair of switches 1016 is moved to the lower position, thereby taking the gates 1017 out of circuit.

Figure 13 The processing system 401 is shown in Figure 13, configured for the music sub mode 802M. From a switching perspective, the topology is substantially the same as that described with reference to Figure 12. However, a new control signal is supplied on control line 415, increasing the maximum sound pressure level to 120 Db. The response of equalisers 1001 to 1004 is also substantially the same as that specified for the vocal sub mode.

In an embodiment, changes are made to the compressing circuit 1018. The threshold is set to -22bD with a ratio of 10:1, introducing significantly more compression to the dynamic range. A knee is present at 22dB, the attack is 5ms and the release is 60ms.

Figure 14 The processing system 401 is shown in Figure 14, modified in response to the immersive mode 803 being selected. This results in the third set of switches 1013 being placed in the lower position, such that an output is derived at 444 via the second signal paths 1012. Within the immersive mode 803, the four sub modes of group 803G, solo 803S, vocal 803V and music 803M may be selected.

Although switching operations within the first signal paths 1011 have no effect, the other modifications previously described continue to be implanted, as described with reference to Figures 10 to 13.

Thus, as the sub modes within the immersive mode 803 are selected, changes are made to signals on the control line 415, changes are made to the equalisers 431 to 434 and changes are made to the compressing circuit 1018.

Figure 15 The properties of the equalisers 1001 to 1004 may be represented as a frequency response, as shown in Figure 15. In this embodiment, a first frequency response 1501 is selected for the group sub modes and for the solo sub modes. A second frequency response 1502 is selected for the vocal sub modes and the music sub modes.

A first frequency response 1501 provides a low shelf 1503 of +6dB at Hz with a Q of 0.8. The low shelf 1503 boosts the signal but has a flat response, unlike a low-pass filter. This is followed by a boost 1504 at 13 kHz with a Q of 0.71. The frequency response may then be followed by a high shelf. These frequency responses aim to optimise the intelligibility of received speech but the actual nature of the compensation required will be determined empirically, given that its main purpose is to compensate for nonlinearities in the microphone capsules 101 to 104.

In the second frequency response 1502, a similar low shelf 1513 is present at 1.4kHz, followed by a peak 1514, an attenuation 1515 and a further higher peak 1516 at 12.3 kHz.

Thus, when receiving a solo singing voice or when receiving music from an ensemble, a level of artistic equalisation has been introduced in addition to the compensating equalisation. This effectively boosts the low frequencies and boosts the higher frequencies, while attenuating the midrange frequencies.

Figure 16 The apparatus described, facilitates the deployment of a method of receiving sound from a plurality of participants. Initially, the apparatus is located at a position for being substantially surrounded by the participants; reducing the requirement to move the microphone when a particular participant is speaking. Audio signals are received from an output interface 107 which are supplied to the external device 442. A plurality of microphone capsules are provided, with each microphone capsule including a receptive face most receptive to soundwaves approaching substantially normally.

A housing includes a plurality of grilles, behind which the receptive face of each microphone capsule is aligned. A processing system processes the audio input signals received from the microphone capsules to supply the audio output signals to the output interface. Each grille and the respective face of its aligned microphone capsule, is inclined with respect to a horizontal plane and the grilles are mutually displaced around the vertical axis.

In operation, an initialisation takes place at step 1601 following the insertion of a USB plug 501. In response to manual interaction, as previously described, mode selection is made at step 1602, such that the apparatus is then operational.

In a preferred embodiment, the processing system 401 operates in response to executing stored instructions which may rely on a significant degree of processing being conducted in a multitasking environment upon a single central processing unit or, in the preferred implementation, a degree of multiprocessing being performed and coordinated to provide substantially real-time signal processing.

At step 1603, equalisation is applied to an input signal and at step 1604 a question is asked as to whether another input signal is present. When answered in the affirmative, further equalisation is provided with respect to the next input signal and the question asked at step 1604 will be answered in the negative when all of the inputs have been considered. In the embodiment previously described, a total of four input signals are received.

At step 1605, the maximum input level is controlled, sending an output control signal on line 415 to the analogue amplifiers 411 to 414.

At step 1606, gating and compressing is performed and at step 1607 an output is supplied to the USB interface 107 by the first signal paths 1011 or via the second signal paths 1012.

If required, a headphone output is processed at step 1608 involving further amplification (1101, 1102) mixing (111, 112) and a further amplification of the mix (1123, 1124). The procedure is then available to receive further input data for mode selection or for processing further audio samples.

In an embodiment, the equalisation step 1603 may compensate the frequency response of the microphones and may also assist in removing undesired vocalisations. Equalisation may also be used to enhance musical performances when the vocal sub mode or the music sub mode is selected. In an embodiment, the individual microphone output signals are combined to form a stereo mix. In addition, a headphone signal may be received combining local loopback with external signals received from a remote source (when conferencing) or in the form of a fold back signal, when recording.

Claims (25)

1. CLAIMSThe invention claimed is: 1. An apparatus for receiving sound from a plurality of participants, comprising: a plurality of microphone capsules, wherein each said microphone capsule includes a receptive face and said receptive face is most receptive to sound waves approaching said face substantially normally; a housing including a plurality of housing grilles, wherein the receptive face of each said microphone capsule is aligned behind a respective housing grille; a processing system for processing audio input signals from said microphone capsules to supply audio output signals to an output interface; wherein: each said housing grille and the respective face of its aligned microphone capsule is inclined with respect to a horizontal plane; and said housing grilles are mutually displaced around a vertical axis.
2. 2. The apparatus of claim 1, wherein said microphone capsules have a substantially cardioid response.
3. 3. The apparatus of claim 1 or claim 2, further comprising a frame for supporting said microphone capsules, wherein each said microphone capsule is supported in said frame by an elastomeric material.
4. 4. The apparatus of any of claims 1 to 3, comprising more than two housing grilles and less than nine housing grilles.
5. 5. The apparatus of claim 4, comprising four housing grilles mutually displaces by ninety degrees around said vertical axis.
6. 6. The apparatus of any of claims 1 to 5, wherein each said housing grille is inclined with respect to said horizontal plane by an angle greater than thirty degrees.
7. 7. The apparatus of any of claims 1 to 5, wherein each said housing grille is inclined with respect to said horizontal plane by an angle of less than sixty degrees.
8. 8. The apparatus of any of claims 1 to 5, wherein each said housing grille is inclined with respect to said horizontal plane by an angle of substantially forty-five degrees.
9. 9. The apparatus of any of claims 1 to 8, wherein said inclined housing grilles extend from a substantially flat base defining a regular shape to a smaller substantially flat top of the same regular shape.
10. 10. The apparatus of claim 9, when dependent of claim 5, wherein said regular shape is a square.
11. 11. The apparatus of claim 9 or claim 10, wherein said substantially flat top comprises: a manually receptive input device for supplying control data to said processing system; and a visual indicating device to display output data from said processing system.
12. 12. The apparatus of any of claims 1 to 11, wherein said processing system includes analogue-to-digital converters for digitizing said audio input signals, such that said audio output signals are digital signals.
13. 13. The apparatus of claim 12, wherein said processing system includes a processor for manipulating said digitized audio input signals in response to stored instructions.
14. 14. The apparatus of claim 13, wherein said processing system is configured to equalize said digital audio input signals to change their frequency distribution.
15. 15. The apparatus of claim 13 and claim 14, wherein said processing system is configured to mix said digital audio input signals to produce a stereo output signal.
16. 16. A method of receiving sound from a plurality of participants, comprising the steps of: locating an apparatus at a position for being substantially surrounded by said participants; and receiving audio output signals from an output interface of said apparatus, wherein said apparatus comprises: a plurality of microphone capsules, wherein each said microphone capsule includes a receptive face and said receptive face is most receptive to sound waves approaching said face substantially normally; a housing including a plurality of housing grilles, wherein the receptive face of each said microphone capsule is aligned behind a respective housing grille; a processing system for processing audio input signals from said microphone capsules to supply said audio output signals to said output interface; wherein: each said housing grille and the respective face of its aligned microphone capsule is inclined with respect to a horizontal plane; and said housing grilles are mutually displaced around a vertical axis.
17. 17. The method of claim 16, further comprising the step of supplying said audio output signals to an external device, non-exclusively selected from a list including: an audio recorder; a video recorder; an amplifier; a public address system; a telecommunication system and a computer.
18. 18. The method of claim 16 or claim 17, comprising the step of digitizing the audio input signals.
19. 19. The method of claim 18, comprising the step of equalizing each digitized audio input signal.
20. 20. The method of claim 19, wherein said equalizing step compensates the frequency responses of said microphones.
21. 21. The method of claim 19, wherein said equalizing step removes undesired vocalizations.
22. 22. The method of claim 19, wherein said equalization step enhances the frequency response with respect to a musical performance.
23. 23. The method of any of claims 16 to 22, comprising the step of mixing said audio input signals, such that said audio output signals are a stereo mix.
24. 24. The method of claim 23, wherein individual microphone output signals are included with said stereo mix.
25. 25. The method of any of claims 16 to 24, further comprising the step of providing an analogue foldback signal to a headphone output interface.Amended claims have been filed as follows:CLAIMS1. An apparatus for receiving sound from a plurality of participants, comprising: a plurality of microphone capsules, wherein each said microphone capsule includes a receptive face and said receptive face is most receptive to sound waves approaching said face substantially normally; a housing including a plurality of housing grilles, wherein the receptive face of each said microphone capsule is aligned behind a respective housing grille; and a processing system for processing audio input signals from said microphone capsules to supply audio output signals to an output interface, wherein: each said housing grille and the respective face of its aligned microphone capsule is inclined with respect to a horizontal plane; and said housing grilles are mutually displaced around a vertical axis and extend from a substantially flat base defining a regular shape to a smaller substantially flat top of the same regular shape, wherein said substantially flat top comprises a manually receptive input device for supplying control data to said processing system and a visual indicating device for displaying output data from said processing system.2. The apparatus of claim 1, wherein said microphone capsules have a substantially cardioid response.3. The apparatus of claim 1 or claim 2, further comprising a frame for supporting said microphone capsules, wherein each said microphone capsule is supported in said frame by an elastomeric material.4. The apparatus of any of claims 1 to 3, comprising more than two housing grilles and less than nine housing grilles.5. The apparatus of claim 4, comprising four housing grilles mutually displaces by ninety degrees around said vertical axis.6. The apparatus of any of claims 1 to 5, wherein each said housing grille is inclined with respect to said horizontal plane by an angle greater than thirty degrees.7. The apparatus of any of claims 1 to 5, wherein each said housing grille is inclined with respect to said horizontal plane by an angle of less than sixty degrees.8. The apparatus of any of claims 1 to 5, wherein each said housing grille is inclined with respect to said horizontal plane by an angle of substantially forty-five degrees.9. The apparatus of claim 1, wherein said regular shape is a square.10. An apparatus for receiving sound from a plurality of participants, comprising: a plurality of microphone capsules, wherein each said microphone capsule includes a receptive face and said receptive face is most receptive to sound waves approaching said face substantially normally; a housing including a plurality of housing grilles, wherein the receptive face of each said microphone capsule is aligned behind a respective housing grille; and a processing system for processing audio input signals from said microphone capsules to supply audio output signals to an output interface, wherein: each said housing grille and the respective face of its aligned microphone capsule is inclined with respect to a horizontal plane; said housing grilles are mutually displaced around a vertical axis; said processing system includes analogue-to-digital converters for digitizing said audio input signals, such that said audio output signals are digital signals; said processing system includes a processor for manipulating said digitized audio input signals in response to stored instructions; and said processing system is configured to mix said digital audio input signals to produce a stereo output signal.11. The apparatus of claim 10, wherein said processing system is configured to equalize said digital audio input signals to change their frequency distribution.12. A method of receiving sound from a plurality of participants, comprising the steps of: locating an apparatus at a position for being substantially surrounded by said participants; and receiving audio output signals from an output interface of said apparatus, wherein said apparatus comprises: a plurality of microphone capsules, wherein each said microphone capsule includes a receptive face and said receptive face is most receptive to sound waves approaching said face substantially normally; a housing including a plurality of housing grilles, wherein the receptive face of each said microphone capsule is aligned behind a respective housing grille; a processing system for processing audio input signals from said microphone capsules to supply said audio output signals to said output interface; wherein: said processing system is configured to mix individual microphone input signals to produce a stereo audio output signal; each said housing grille and the respective face of its aligned microphone capsule is inclined with respect to a horizontal plane; and said housing grilles are mutually displaced around a vertical axis.13. The method of claim 12, further comprising the step of supplying said audio output signals to an external device, non-exclusively selected from a list including: an audio recorder; a video recorder; an amplifier; a public address system; a telecommunication system and a computer.14. The method of claim 12 or claim 13, comprising the step of digitizing the audio input signals.15. The method of claim 14, comprising the step of equalizing each digitized audio input signal.16. The method of claim 15, wherein said equalizing step compensates the frequency responses of said microphones.17. The method of claim 15, wherein said equalizing step removes undesired vocalizations.18. The method of claim 15, wherein said equalization step enhances the frequency response with respect to a musical performance.19. The method of any of claims 12 to 18, further comprising the step of providing an analogue foldback signal to a headphone output interface.