Simplified communication system

• US 6,295,364 B1
• Filed: 03/30/1998
• Issued: 09/25/2001
• Est. Priority Date: 03/30/1998
• Status: Expired due to Term

• Current Assignee: Digisonix Incorporated
• Original Assignee: Digisonix Incorporated
• Inventors: Roe, Thomas O., Nowak, Michael P., Finn, Brian M.
• Primary Examiner(s): Isen, Forester W.
• Assistant Examiner(s): PENDLETON, BRIAN T
• Application Number:
  US09/050,511
• Time in Patent Office: 1,275 Days
• Field of Search: 381/71.4, 381/71.1, 381/57, 381/110, 381/86, 379/406, 379/410, 379/409
• US Class Current: 381/110
• CPC Class Codes: G10L 21/0208 Noise filtering
• CPC Class Codes: G10L 21/0232 Processing in the frequency domain
• CPC Class Codes: H04M 9/08 Two-way loud-speaking telephone systems with means for conditioning the signal, e.g. for suppressing echoes for one or both directions of traffic

Abstract

A digital voice enhancement communication system, including a simplex system, has first and second acoustic zones, and respective microphones and loudspeakers. A voice sensitive gated switch has a first mode supplying the output of a first microphone in the first zone over a first channel to a second loudspeaker in the second zone, and has a second mode supplying the output of a second microphone in the second zone over a second channel to the first loudspeaker in the first zone. First and second noise sensitive bandpass filters and first and second equalization filters are provided in the first and second channels, respectively. Each noise sensitive bandpass filter is a noise responsive highpass filter having a filter cutoff effective at elevated noise levels and reducing bandwidth and making more gain available, to improve intelligibility of speech of a person in the respective zone transmitted from the respective microphone to the loudspeaker in the other zone. Each equalization filter reduces resonance peaks in the acoustic transfer function between the receiving loudspeaker in the other zone and the sending microphone in the one zone to reduce feedback by damping resonance peaks.

Claims

1. A simplex digital voice enhancement communication system comprising in combination:

a first acoustic zone;

a second acoustic zone;

a first microphone in said first zone;

a first loudspeaker in said first zone, said first loudspeaker being acoustically coupled to said first microphone;

a second microphone in said second zone;

a second loudspeaker in said second zone, said second loudspeaker being acoustically coupled to said second microphone;

a voice sensitive gated switch having a first mode supplying the output of said first microphone over a first channel to said second loudspeaker, and having a second mode supplying the output of said second microphone over a second channel to said first loudspeaker;

a first noise sensitive bandpass filter in said first channel;

a first equalization filter in said first channel;

a second noise sensitive bandpass filter in said second channel;

a second noise sensitive bandpass filter in said second channel;

a second equalization filter in said second channel;

wherein;

said first microphone is acoustically coupled to said second loudspeaker;

said second microphone is acoustically coupled to said first loudspeaker;

said voice sensitive gated switch comprises two voice activity detector gates, a first gate detecting the output of said first microphone, and a second gate detecting the output of said second microphone.

2. The system according to claim 1 wherein:

said voice sensitive gated switch in said first mode substantially blocks transmission from said second microphone to said first loudspeaker;

said voice sensitive gated switch in said second mode substantially blocks transmission from said first microphone to said second loudspeaker;

said first and second modes of said voice sensitive gated switch are mutually exclusive such that only one of said channels can be active at a time;

said first noise sensitive bandpass filter comprises a noise responsive highpass filter having a filter cutoff effective at elevated noise levels and reducing bandwidth and making more gain available, to improve intelligibility of speech of a first person in said first zone transmitted from said first microphone to said second loudspeaker;

said first equalization filter reduces resonance peaks in the acoustic transfer function between said second loudspeaker in said second zone and said first microphone in said first zone to reduce feedback by damping resonance peaks;

said second noise sensitive bandpass filter comprises a second noise responsive highpass filter having a filter cutoff effective at elevated noise levels and reducing bandwidth and making more gain available, to improve intelligibility of speech of a second person in said second zone transmitted from said second microphone to said first loudspeaker;

said second equalization filter reduces resonance peaks in the acoustic transfer function between said first loudspeaker in said first zone and said second microphone in said second zone to reduce feedback by damping resonance peaks.

3. The system according to claim 2 wherein:

said first equalization filter comprises a first spectral transfer function;

said second equalization filter comprises a second spectral transfer function.

4. The system according to claim 2 wherein:

said first equalization filter comprises a set of one or more frequency selective notch filters determined from said acoustic transfer function between said second loudspeaker in said second zone and said first microphone in said first zone;

said second equalization filter comprises a set of one or more frequency selective notch filters determined from said acoustic transfer function between said first loudspeaker in said first zone and said second microphone in said second zone.

5. A simplex digital voice enhancement communication system comprising in combination:

a first acoustic zone;

a second acoustic zone;

a first microphone in said first zone;

a first loudspeaker in said first zone;

a second microphone in said second zone;

a second loudspeaker in said second zone;

a voice sensitive gated switch having a first mode supplying the output of said first microphone over a first channel to said second loudspeaker, and having a second mode supplying the output of said second microphone over a second channel to said first loudspeaker;

a first noise sensitive bandpass filter in said first channel;

a first equalization filter in said first channel;

a second noise sensitive bandpass filter in said second channel;

a second noise sensitive bandpass filter in said second channel;

a second equalization filter in said second channel,

wherein;

said voice sensitive gated switch in said first mode substantially blocks transmission from said second microphone to said first loudspeaker;

said voice sensitive gated switch in said second mode substantially blocks transmission from said first microphone to said second loudspeaker;

said first and second modes of said voice sensitive gated switch are mutually exclusive such that only one of said channels can be active at a time;

said first noise sensitive bandpass filter comprises a noise responsive highpass filter having a filter cutoff effective at elevated noise levels and reducing bandwidth and making more gain available, to improve intelligibility of speech of a first person in said first zone transmitted from said first microphone to said second loudspeaker;

said first equalization filter reduces resonance peaks in the acoustic transfer function between said second loudspeaker in said second zone and said first microphone in said first zone to reduce feedback by damping resonance peaks;

said second noise sensitive bandpass filter comprises a second noise responsive highpass filter having a filter cutoff effective at elevated noise levels and reducing bandwidth and making more gain available, to improve intelligibility of speech of a second person in said second zone transmitted from said second microphone to said first loudspeaker;

said second equalization filter reduces resonance peaks in the acoustic transfer function between said first loudspeaker in said first zone and said second microphone in said second zone to reduce feedback by damping resonance peaks;

said system is in a vehicle, and each of said first and second highpass filters is vehicle speed sensitive,

such that at higher vehicle speeds and resulting higher noise levels, lower frequency speech content of vehicle occupants is blocked and higher frequency speech content of vehicle occupants is passed, the lower frequency speech content of vehicle occupants being otherwise masked at higher speeds by broadband vehicle and wind noise, so that the reduced bandwidth and the absence of the lower frequency speech content of vehicle occupants does not sacrifice the perceived quality of speech,

and such that at lower vehicle speeds and resulting lower noise levels, the cutoff frequency of each of said first and second highpass filters is lowered such that lower frequency speech content of vehicle occupants is passed, in addition to higher frequency speech content of vehicle occupants, to provide enriched low frequency performance, and overcome objections to a tinny sounding system in said vehicle;

wherein;

said first microphone is acoustically coupled to said second loudspeaker;

said second microphone is acoustically coupled to said first loudspeaker;

said voice sensitive gated switch comprises two voice activity detector gates, a first gate detecting the output of said first microphone, and a second gate detecting the output of said second microphone.

6. The system according to claim 5, wherein said vehicle has a speedometer, and each of said first and second highpass filters is responsive to said speedometer.

7. A simplex digital voice enhancement communication system comprising in combination:

a first acoustic zone;

a second acoustic zone;

a first microphone in said first zone;

a first loudspeaker in said first zone;

a second microphone in said second zone;

a second loudspeaker in said second zone;

a voice sensitive gated switch having a first mode supplying the output of said first microphone over a first channel to said second loudspeaker, and having a second mode supplying the output of said second microphone over a second channel to said first loudspeaker;

a first noise sensitive bandpass filter in said first channel;

a first equalization filter in said first channel;

a second noise sensitive bandpass filter in said second channel;

a second noise sensitive bandpass filter in said second channel;

a second equalization filter in said second channel,

wherein;

said voice sensitive gated switch in said first mode substantially blocks transmission from said second microphone to said first loudspeaker;

said voice sensitive gated switch in said second mode substantially blocks transmission from said first microphone to said second loudspeaker;

said first and second modes of said voice sensitive gated switch are mutually exclusive such that only one of said channels can be active at a time;

said first noise sensitive bandpass filter comprises a noise responsive highpass filter having a filter cutoff effective at elevated noise levels and reducing bandwidth and making more gain available, to improve intelligibility of speech of a first person in said first zone transmitted from said first microphone to said second loudspeaker;

said first equalization filter reduces resonance peaks in the acoustic transfer function between said second loudspeaker in said second zone and said first microphone in said first zone to reduce feedback by damping resonance peaks;

said second noise sensitive bandpass filter comprises a second noise responsive highpass filter having a filter cutoff effective at elevated noise levels and reducing bandwidth and making more gain available, to improve intelligibility of speech of a second person in said second zone transmitted from said second microphone to said first loudspeaker;

said second equalization filter reduces resonance peaks in the acoustic transfer function between said first loudspeaker in said first zone and said second microphone in said second zone to reduce feedback by damping resonance peaks;

said system is in a vehicle, and each of said first and second highpass filters is vehicle speed sensitive,

such that at higher vehicle speeds and resulting higher noise levels, lower frequency speech content is blocked and higher frequency speech content is passed, the lower frequency speech content being otherwise masked at higher speeds by broadband vehicle and wind noise, so that the reduced bandwidth and the absence of the lower frequency speech content does not sacrifice the perceived quality of speech,

and such that at lower vehicle speeds and resulting lower noise levels, the cutoff frequency of each of said first and second highpass filters is lowered such that lower frequency speech content is passed, in addition to higher frequency speech content, to provide enriched low frequency performance, and overcome objections to a tinny sounding system in said vehicle;

said vehicle has an in-cabin audio system, and comprising a digital voice enhancement activation switch actuating said voice sensitive gated switch and providing an audio mute signal muting said in-cabin audio system;

wherein;

said first microphone is acoustically coupled to said second loudspeaker;

said second microphone is acoustically coupled to said first loudspeaker;

said voice sensitive gated switch comprises two voice activity detector gates, a first gate detecting the output of said first microphone and a second gate detecting the output of said second microphone.