METHOD AND SYSTEM FOR REDUCING ACOUSTICAL REVERBERATIONS IN AN AT LEAST PARTIALLY ENCLOSED SPACE

• US 20110129096A1
• Filed: 11/30/2009
• Published: 06/02/2011
• Est. Priority Date: 11/30/2009
• Status: Active Grant

• Current Assignee: Emmet Raftery
• Original Assignee: Emmet Raftery
• Inventors: Raftery, Emmet
• Granted Patent: US 8,553,898 B2
• Time in Patent Office: Days
• US Class Current: 381/66
• CPC Class Codes: G10K 11/17854 the filter being an adaptive filter
• CPC Class Codes: G10K 11/17857 Geometric disposition, e.g. placement of microphones
• CPC Class Codes: G10K 11/17881 the reference signal being an acoustic signal, e.g. recorded with a microphone
• CPC Class Codes: G10K 2210/12 Rooms, e.g. ANC inside a room, office, concert hall or automobile cabin
• CPC Class Codes: G10K 2210/505 Echo cancellation, e.g. multipath-, ghost- or reverberation-cancellation

Abstract

A method of increasing the intelligibility of an audio broadcast in an at least partially enclosed space from at least one amplified audio source. An input microphone receives an incident audio wavefront at a first position in the at least partially enclosed space. An active noise control system is employed to generate a cancelling audio wavefront having a magnitude substantially equal to the magnitude of incident audio wavefront and a phase substantially opposite to the phase of the incident audio wavefront. The cancelling audio wavefront is broadcast at a second position in the at least partially enclosed space adjacent to a reflective surface of the at least partially enclosed space so as to attenuate the incident audio wavefront substantially at or near the reflective surface in order to reduce reverberations of the incident audio wavefront. In this manner, reverberations which could reduce the intelligibility of the audio broadcast to an audience is reduced.

Claims

1. A method of increasing the intelligibility of an audio broadcast in an at least partially enclosed space from at least one amplified audio source, the method comprising:

receiving an incident audio wavefront from the amplified audio source at a first position in the at least partially enclosed space;

generating a cancelling audio wavefront having a magnitude substantially equal to the magnitude of incident audio wavefront and a phase substantially opposite to the phase of the incident audio wavefront; and

broadcasting the cancelling audio wavefront at a second position in the at least partially enclosed space, the second position being adjacent to a reflective surface of the at least partially enclosed space and downstream of the first position relative to the audio source, thereby to attenuate the incident audio wavefront substantially at or near the reflective surface in order to reduce reverberations of the incident audio wavefront.

2. A method according to claim 1, wherein the incident audio wavefront is received via at least one input microphone.

3. A method according to claim 2, wherein the cancelling audio wavefront is broadcast through at least one directional loudspeaker positioned adjacent to, and facing, the reflective surface.

4. A method according to claim 3, wherein the cancelling loudspeaker is spaced at a distance D away from the input microphone, D corresponding to the delay time required to generate the cancelling audio wavefront.

5. A method according to claim 4, wherein an array of input microphones and corresponding cancelling loudspeakers are deployed across the breadth of the reflective surface.

6. A method of increasing the intelligibility of an audio broadcast in an at least partially enclosed space from at least one amplified audio source, the method comprising:

deploying at least one input microphone in the at least partially enclosed space to convert at least one incident audio wavefront into at least one corresponding reference electrical signal;

deploying at least one cancelling loudspeaker adjacent a reflective surface in the at least partially enclosed space to broadcast at least one secondary audio wavefront;

deploying at least one error microphone substantially at the reflective surface to convert a superposition of the at least one incident audio wavefront and the at least one secondary audio wavefront into at least one error electrical signal;

generating at least one cancellation signal based on the at least one reference electrical signal so as to minimize the power of the at least one error electrical signal; and

converting the cancellation signal into said at least one second audio wavefront.

7. A method according to claim 6, wherein each cancelling loudspeaker is positioned adjacent to the reflective surface and has a highly directional output directed downstream of the incident audio source.

8. A method according to claim 7, wherein each cancelling loudspeaker is spaced at least a distance D away from a corresponding input microphone, where D corresponds to the delay time required to generate the cancelling audio wavefront.

9. A method according to claim 7, wherein an array of input microphones, an array of cancelling loudspeakers, and an array of error microphones are deployed across the breadth of the reflective surface.

10. A method according to claim 9, wherein the number of input microphones, cancelling loudspeakers and error microphones are equal.

11. A method according to claim 10, wherein, each input microphone, cancelling speaker and error microphone triplet form an independent, single-channel, sound dampening unit, and a plurality of single channel sound dampening units are deployed across the breadth of the reflective surface.

12. A method according to claim 9, wherein the input microphones, cancelling loudspeakers and error microphones are interlinked via a multiple-channel active sound control module.

13. A method of broadcasting audio with reduced reverberation in an at least partially enclosed space, the method comprising:

broadcasting an incident audio wave from at least one amplified audio source;

transmitting a signal that is representative of the audio to a control module;

generating, using the control module, a cancelling audio wave having a magnitude substantially equal to the magnitude of incident audio wave and a phase substantially opposite to the phase of the incident audio wave; and

broadcasting the cancelling audio wave from a position adjacent to a reflective surface of the at least partially enclosed space and downstream from the at least one amplified audio source, thereby attenuating the incident audio wave substantially at or near the reflective surface in order to reduce reverberations of the incident audio wave.