# US 12,120,273 B2 · Distributed network of ceiling image-derived directional microphones

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- Number: US 12,120,273 B2
- Document ID: US12120273B2
- Status: Granted
- Kind: B2
- Application number: 17/843,296
- Filed: 2022-06-17
- Published: 2023-12-21
- Granted: 2024-10-15
- Earliest claimed: 2022-06-17
- Assignees: Hewlett-Packard Development Company, L.P.
- Applicants: Hewlett-Packard Development Company, L.P.
- Inventors: Peter L. Chu; Jay McArdle
- Web page: https://patentgrep.com/patent/US12120273B2

## CPC

- H04M 3/568: {audio processing specific to telephonic conferencing, e.g. spatial distribution, mixing of participants (echo suppression in two-way loud-speaking telephone systems H04M9/02; sound field processing per se H04S7/30)}
- H04R 1/025: {Arrangements for fixing loudspeaker transducers, e.g. in a box, furniture}
- H04R 1/342: {for microphones}
- H04R 1/403: {loud-speakers}
- H04R 1/406: {microphones}
- H04R 3/005: {for combining the signals of two or more microphones (specially adapted for hearing aids H04R25/407)}
- H04R 3/12: for distributing signals to two or more loudspeakers {(specially adapted for hearing aids H04R25/407)}
- H04R 27/00: Public address systems (circuits for preventing acoustic reaction H04R3/02; circuits for distributing signals to loudspeakers H04R3/12; {monitoring or testing arrangements for public address systems H04R29/007}; amplifiers H03F)
- H04R 29/005: {Microphone arrays}
- H04R 2201/021: Transducers or their casings adapted for mounting in or to a wall or ceiling
- H04R 2201/401: 2D or 3D arrays of transducers
- H04M: TELEPHONIC COMMUNICATION (circuits for controlling other apparatus via a telephone cable and not involving telephone switching apparatus G08)
- H04R: LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS (producing sounds with frequency not determined by supply frequency G10K)

## Abstract

A method and apparatus for capturing audio including a ceiling mountable second-order differential microphone module. The module including a solid planar baffle having a generally centered aperture, at least one mounting foot to suspend the solid planar baffle approximately parallel with a rear reflecting plane and to space the solid planar baffle at a predetermined distance below the rear reflecting plane, a differential microphone sealably coupled to the planar baffle with a first side of the differential microphone acoustically exposed to an area above the planar baffle and a second side of the differential microphone acoustically exposed to an area below the planar baffle, and a mounting means for mounting the solid rear reflecting panel to the room ceiling.

## Claims

### Claim 1

An audio system comprising:
a loudspeaker; and
a sound capture device comprising:
a solid rear reflecting plane mountable to a room ceiling,
a solid planar baffle parallel with the rear reflecting plane and spaced at a distance below the rear reflecting plane, the planar baffle having a generally centered aperture,
a differential microphone sealably coupled to the planar baffle with a first side of the differential microphone acoustically exposed to an area above the planar baffle and a second side of the differential microphone acoustically exposed to an area below the planar baffle, and
a mounting means for mounting the solid rear reflecting panel to the room ceiling.

### Claim 2 (depends on 1)

The system of claim 1, wherein the sound capture device is incorporated into a drop ceiling tile along with the loudspeaker having a diameter at least approximately 6.7″.

### Claim 3 (depends on 1)

The system of claim 1, wherein the solid planar baffle is circular with a diameter of approximately 1.75″ and is spaced approximately 0.5″ from the rear reflecting plane and wherein the microphone is a cardioid electret capsule.

### Claim 4 (depends on 1)

The system of claim 1, comprising a ceiling mountable omnidirectional microphone, a ceiling mountable loudspeaker, and a controller comprising a plurality of microphone inputs and a sound nullifying circuit to:
receive a first microphone signal corresponding to the sound capture device and a second microphone signal from the omnidirectional microphone, and
subtract the second microphone signal from the first microphone signal.

### Claim 5 (depends on 1)

The system of claim 1, further comprising a controller for receiving a plurality of microphone signals and a processor operable to:
receive a first microphone signal corresponding to the sound capture device and a second microphone signal from a second sound capture device,
determine which of the first and second microphone signal has the highest energy in each of a plurality of frequency bands,
select the microphone signal having the highest energy in the majority of the plurality of frequency bands, and
output the selected microphone signal.

### Claim 6 (depends on 5)

The system of claim 5, wherein the plurality of frequency bands comprises 25 Hz wide sub bands spanning 500 Hz to 1500 Hz.

### Claim 7 (depends on 5)

The system of claim 5, wherein:
the controller comprises a plurality of speaker outputs to drive a first speaker mounted within two feet of the sound capture device and a second speaker mounted within two feet of the second sound capture device, and
the controller operable to transmit the selected microphone signal to a remote conferencing location, receive an audio signal from the remote conferencing location, and output the received audio signal to the plurality of speaker outputs as part of a two-way audio conference.

### Claim 8 (depends on 7)

The system of claim 7, wherein the controller is operable to transmit the selected microphone signal while outputting the received audio signal.

### Claim 9

An apparatus comprising:
a drop ceiling tile;
a solid rear reflecting plane;
a loudspeaker; and
a first sound capture device affixed to the ceiling tile, the first sound capture device comprising:
a solid planar baffle parallel with the solid rear reflecting plane and spaced at a distance below the solid rear reflecting plane, the solid planar baffle having a generally centered aperture, and
a differential microphone sealably coupled to the solid planar baffle with a first side of the differential microphone acoustically exposed to an area above the solid planar baffle and a second side of the differential microphone acoustically exposed to an area below the planar baffle.

### Claim 10 (depends on 9)

The apparatus of claim 9, wherein a lower surface of the drop ceiling tile forms the solid rear reflecting plane.

### Claim 11 (depends on 9)

The apparatus of claim 9, wherein the loudspeaker has a diameter of at least approximately 6.7″.

### Claim 12 (depends on 11)

The apparatus of claim 11, comprising:
an omnidirectional microphone installed between the loudspeaker and the sound capture device; and
a sound nullifying circuit to, for each of a plurality of frequency bands:
adjust the phase of sound captured by the omnidirectional microphone,
adjust the amplitude of sound captured by the omnidirectional microphone, and
subtract the phase and amplitude adjusted sound captured by the omnidirectional microphone from the sound captured by the first sound capture device.

### Claim 13 (depends on 9)

The apparatus of claim 9, wherein the solid planar baffle is circular with a diameter of approximately 1.75″ and is spaced approximately 0.5″ from the rear reflecting plane and wherein the microphone is a cardioid electret capsule.

### Claim 14 (depends on 9)

The apparatus of claim 9, wherein the solid rear reflecting plane is the lower surface of the ceiling tile.

### Claim 15 (depends on 9)

The apparatus of claim 9, comprising a microphone selection circuit to:
receive a first signal from the first sound capture device,
receive a second signal from a second sound capture device,
determine which of the first and second signal has the highest energy in each of a plurality of frequency bands,
select either the first or second signal based on which has the highest energy in the majority of the plurality of frequency bands, and
output the selected signal.

### Claim 16 (depends on 15)

The apparatus of claim 15, wherein the plurality of frequency bands comprises 25 Hz wide sub bands spanning 500 Hz to 1500 Hz.

### Claim 17 (depends on 11)

The apparatus of claim 11, wherein the loudspeaker has a diameter at least approximately 6.7″.

### Claim 18

A method, comprising:
mounting to a ceiling a first differential sound capture device comprising a rear reflecting plane, a circular planar baffle parallel mounted parallel to and spaced approximately less than an inch from the rear reflecting plane, and a differential microphone sealed in the center of the baffle and acoustically exposed to each side of the baffle,
mounting to the ceiling a second differential sound capture device wherein the second sound capture device is mounted at least four feet from the first sound capture device,
mounting a loudspeaker to the ceiling, and
coupling the first and second sound capture devices to a conferencing system, and
coupling the loudspeaker to the conferencing system.

### Claim 19 (depends on 18)

The method of claim 18, comprising:
mounting an omnidirectional microphone to the ceiling approximately on a line between the center of the differential microphone and the loudspeaker;
adjusting the phase of sound captured by the omnidirectional microphone;
adjusting the amplitude of sound captured by the omnidirectional microphone; and
subtracting the phase and amplitude adjusted sound captured by the omnidirectional microphone from the sound captured by the sound capture device.

### Claim 20 (depends on 18)

The method of claim 18, comprising:
receiving a first signal from the first differential sound capture device,
receiving a second signal from the second differential sound capture device,
determining which of the first and second signal has the highest energy in each of a plurality of frequency bands,
selecting either the first or second signal based on which has the highest energy in the majority of the plurality of frequency bands, and
outputting the selected signal.