Audio system for conferencing/presentation room

• US 5,848,146 A
• Filed: 05/10/1996
• Issued: 12/08/1998
• Est. Priority Date: 05/10/1996
• Status: Expired due to Term

• Current Assignee: RANE Limited (RANE Holdings Limited)
• Original Assignee: RANE Limited (RANE Holdings Limited)
• Inventors: Slattery, Ernest Michael
• Primary Examiner(s): Hunter, Daniel S.
• Assistant Examiner(s): SAINT SURIN, JACQUES M
• Application Number:
  US08/644,233
• Time in Patent Office: 942 Days
• Field of Search: 379/406, 379/410, 379/202, 379/388, 379/390, 379/203, 379/204, 379/205, 379/206, 379/389, 370/285, 370/286, 370/287, 370/288, 370/289, 370/290, 370/291, 370/292, 371/110, 371/119
• US Class Current: 379/406.01
• CPC Class Codes: H04H 60/04 Studio equipment; Interconnection of studios
• CPC Class Codes: H04M 3/002 Applications of echo suppressors or cancellers in telephonic connections in two-way loud-speaking telephone systems H04M9/08, echo suppressors or cancellers per se H04B3/20
• CPC Class Codes: H04M 3/56 Arrangements for connecting several subscribers to a common circuit, i.e. affording conference facilities video conference systems H04N7/15
• CPC Class Codes: 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
• CPC Class Codes: H04M 9/082 using echo cancellers echo cancellers per se H04B3/23

Abstract

A multiport bridge controlled by the intelligence of a programmed microcontroller selectively channels audio from a plurality of input ports to a plurality of output ports including a room program output. Coupled to one of the bridge input ports is at least one gated microphone mixer, including multiple microphone channels and an acoustical echo canceller. Expandability is provided by a second, third or up to n microphone mixers each having a separate echo canceller for the associated group of microphone inputs.

Claims

1. An audio conferencing control system for full-duplex communication of multiple audio signal sources between near-end and far-end, for use with room microphones that produce near-end audio sources and telecommunication equipment that transmits near-end audio sources to a far-end and receives far-end audio sources for conversion to sound by room loudspeakers, comprising:

a controlled microphone mixer having a mixer output and a plurality of microphone input channel means for receiving and detecting audio signals produced by sound including speech at near-end microphones, and means for selectively gating on each of said microphone input channel means in response to the audio signals and controlled channel thresholds, and signal summing means for combining gated microphone input channel signals from said input channel means into said mixer output;

an echo canceller means at said mixer output for cancelling echo signals due to near-end microphone pick up of far-end audio signal source from a room loudspeaker, said echo canceller means having a reference signal input;

a controlled multiport audio bridge having a plurality of input and output port means including a first input port means connected to the mixer output after said echo canceller means, a second input port means for receiving a far-end audio signal source, a first output port means for applying a far-end audio signal to a room loudspeaker and providing an echo reference signal that is applied to said reference signal input of said echo canceller means, and having a second output port means for outputting a near-end audio program signal for transmission to a far-end location; and

control means for controlling said microphone mixer and said multiport audio bridge and having programmable and preprogrammed functions including mixer channel threshold controls and audio bridge port selection controls for selectively bridging said audio bridge input ports to said audio bridge output ports, and having communication means for sending and receiving control and status signals for said mixer and bridge.

2. The audio conferencing control system of claim 1 further comprising an additional controlled microphone mixer for expansion and having an additional plurality of microphone input channel means for receiving and detecting audio signals produced by sound including speech at an associated plurality of near-end microphones, said additional controlled microphone mixer having an additional mixer output;

an additional echo canceller means at said additional mixer output for cancellation of echo signals due to near-end microphone pick up of far-end audio signal source from a room loudspeaker, said additional echo canceller means having an additional reference signal input; and

means for connecting said additional reference signal input of said additional echo canceller means to said first output port means of said audio bridge.

3. The audio conferencing control system of claim 1 wherein said control means further comprises:

signal level detecting means for detecting an audio input signal level at each of said microphone input channel means of said mixer;

means for detecting an audio present condition at each of said microphone mixer input channel means when a channel audio input signal level is above a controlled channel threshold;

means for setting separate thresholds at each of said input channel means;

means for gating an input channel means on in response to detected audio present condition;

means for producing an audio present control signal representing said audio present condition for each of said input channel means;

means responsive to said audio present control signal for determining the time duration that an input channel means exhibits said audio present condition;

means for producing a master status control signal representing a master channel status after a predetermined time duration of said audio present condition;

means responsive to said audio present control signal representing each of said input channel means for setting increased thresholds at the remaining input channel means; and

means for terminating said master status control signal for an associated input channel means when the audio present control signal for an input channel means has ceased for a predetermined channel release time.

4. The audio conferencing system of claim 3 wherein said control means further comprises port level detection means for detecting the level of an audio signal at each of said input port means of said audio bridge and said control means further having means for producing an active port status signal when said port level detector means detects a port input signal greater than a controlled port threshold at each of said input port means;

and means responsive to a first active port status signal for increasing the port threshold at each other input port means of said audio bridge.

5. The audio conferencing control system of claim 4 wherein said control means further comprises means for determining a master port condition including means for detecting the first active port status signal that continues for more than a predetermined master time duration;

and said control means includes means for producing a master port status signal representing the master port condition.

6. The audio conferencing control system of claim 1 wherein said control means comprises:

means for detecting an audio input signal level at each of said microphone input channel means of said microphone mixer;

means for gating on each of said microphone mixer input channel means when an input signal level is above a controlled channel threshold;

means for producing an audio present condition status signal when the associated channel input means is gated on;

means for controllably setting separate channel thresholds, one for each of said mixer input channel means; and

means for increasing said input channel thresholds by a port output induced channel offset to counteract false detection of an audio present condition at said microphone mixer input channel means when a loudspeaker receives a predetermined level of audio signal level at said first output port means of the audio bridge.

7. The audio conferencing system of claim 6, said control means further comprising means for precomputing and storing port output induced offset values for increasing said input channel thresholds by said port output induced channel offset, and means responsive to said predetermined program audio signal level for adding said port output induced offset values to said means for setting separate channel thresholds.

8. The audio conferencing system of claim 7 wherein said control means comprises a master microprocessor for controlling said multiport audio bridge and a slave microprocessor for controlling said microphone mixer, and wherein said master microprocessor precomputes said port output induced offset values and produces a digital message for causing said port output induced offset values to be added to said channel thresholds by said slave microprocessor whenever said predetermined program audio signal level occurs at said first output port means of the audio bridge.

9. The audio conferencing system of claim 8 further comprising means in said slave processor means for producing input channel offsets for predetermined input channel means after first gating on one of said input channel means of said mixer;

and said slave microprocessor means further comprising means for storing said port output induced offset values, and means for adding said port output induced offset values and said input channel offsets to produce increased input channel thresholds.

10. The audio conferencing control system of claim 1 further comprising output signal level detection means at said first output port means of said audio bridge, and said control means includes output threshold detection means for determining when a program audio signal delivered at said first output port means of said audio bridge rises to a predetermined level and means for producing a port antivox status message signal whenever the signal level at said first output port means reaches said predetermined level, and wherein said means for selectively gating on each of said microphone input channel means in response to controlled channel thresholds includes means for increasing said controlled channel thresholds in response to said port antivox status message signal.

11. The audio conferencing control system of claim 1 wherein said control means generates active status signals for each said input port means and communicates said active status signals via said communication means.

12. The audio conferencing control system of claim 11 wherein said control means further includes means for determining a master port status when any of said input port means exhibit said active port status signal for a predetermined master port time delay, and said control means produces a master port status signal and communicates same via said communication means.

13. The audio conferencing control system of claim 1 further comprising signal level detection means at said plurality of input port means of said multiport audio bridge, and said control means includes means for producing an input port active status signal whenever the input level signal detection means at an associated input port means detects an input port signal level above a predetermined port threshold, and said control means including means responsive to said active status signal at any of said input port means to said audio bridge for increasing the threshold detection level of signals applied to any of the other input port means of said audio bridge whereby when one of said input port means exhibits an active status, said increasing the threshold detection level makes it more difficult for the other input port means of said audio bridge to generate an active status signal.

14. An audio conferencing control system for full-duplex communication of multiple audio signal sources between near-end and far-end, for use with room microphones that produce near-end audio sources and telecommunication equipment that transmits near-end audio sources to a far-end and receives far-end audio sources for conversion to sound by room loudspeakers, comprising:

a base unit including a controlled multiport audio bridge having a plurality of input and output port means including a first input port means for connection of mixed microphone sources, a second input port means for connection of a far-end telecommunication signal source, a first output port means for producing a program audio signal to be applied to a room loudspeaker and for producing an echo reference signal output, and a second output port means for outputting an audio program signal for transmission to a far end;

at least first and second microphone mixer expansion modules each having an output, the first mixer expansion module having a first set of microphone input channel means for receiving and detecting sound including speech at a first plurality of room microphones, and having means for selectively gating on each of said first set of microphone input channel means in response to controlled channel thresholds, and having signal summing means for combining gated microphone signals from said first set of input channel means into the mixer output of said first mixer expansion module;

a first echo canceller means at said output of said first mixer expansion module for cancelling echo signals caused by microphone pick up of far-end audio from a room loudspeaker, said first echo canceller means having a reference signal input connected to said reference signal output of said base unit;

the second mixer expansion module having a second set of microphone input channel means for receiving and detecting sound including speech at a second plurality of room microphones, and having means for selectively gating on each of said second set of microphone input channel means in response to controlled channel thresholds, and having a signal summing means for combining gated microphone signals from said second set of input channel means into the mixer output of said second mixer expansion module;

a second echo canceller means at said output of said second mixer expansion module for cancelling echo signals caused by microphone pick up by the second plurality of room microphones of far-end audio from a room loudspeaker, said second echo canceller means having a reference signal input connected to said reference signal output of said base unit; and

microprocessor control means in said base unit and in each of said mixer expansion modules for controlling said multiport audio bridge and said mixer expansion modules and having programmable and preprogrammed functions including mixer channel threshold controls for gating said microphone input channel means and audio bridge port selection controls for selectively bridging said input port means to said output port means, and having communication means for sending and receiving control and status signals for said mixer input channel means and for said audio bridge input and output port means.

15. A method of full-duplex communication of multiple audio signal sources between near-end and far-end, using room microphones for producing near-end audio signal sources and telecommunication equipment transmitting near-end audio signal sources to far-end and receiving far-end audio signal sources for conversion to sound by room loudspeakers, comprising the steps of:

mixing of a plurality of microphone input channels that receive and detect sound including speech at near-end microphones, and selectively gating on each of said microphone input channels when signals at said input channels are above controlled channel thresholds, and summing signals from the gated microphone input channels to produce a mixer output;

cancelling echo signals at said mixer output due to near-end microphone pick up of far-end audio signal source from a room loudspeaker;

controlling a multiport audio bridge having a plurality of input and output ports that include a first input port connecting the output of said mixing step after said echo cancelling step, a second input port receiving a far-end audio signal source, a first output port applying a far-end audio signal to a loudspeaker and providing an echo reference signal for use by said echo cancelling step, and having a second output port outputting a near-end audio program signal and transmitting same to a far-end location; and

controlling said microphone mixer and said multiport audio bridge by programmable and preprogrammed processes including mixer channel threshold controls and audio bridge port selection controls for selectively bridging said input ports to said output ports, and communicating control and status signals for use in said step of mixing and in controlling said bridge input and output ports.

16. The method of claim 15 further comprising the additional step of mixing an additional plurality of microphone input channels for receiving and detecting sound including speech at an associated additional plurality of near-end microphones, and forming an additional mixer output;

an additional separate step of cancelling echo signals due to pick up by the additional plurality of microphones of far-end audio signal source from a room loudspeaker; and

using said echo reference signal jointly in the first mentioned step of cancelling echos and in said additional separate step of cancelling echos.