US4251685A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Reproduction of sound
Assignee: National Research Development Corp UK
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Filing: 1974-01-03
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Granted: 1981-02-17
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Expires: 1994-01-03
Abstract
Abstract In a sound reproduction system which enables the listener to distinguish between signals from in front and behind as well as signals on the left and the right, only two independent transmission channels are employed. The contributions to the signals in the two transmission channels relating to a sound source at a particular azimuth have the same amplitude and frequency and differ in phase by an amount indicating the azimuth of such source.
Inventors
- 👤 Peter B. Fellgett
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 21:40
CPC Classifications
H; H04; H04S; H04S3/00; H04S3/02
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
263 words
A transmitter for a multi-channel sound reproduction system for generating a plurality of audio signals each corresponding to a respective audio source at a particular azimuth with respect to a reference point and having two transmission channels, comprising: means for forming a first signal component by adding together all the plurality of audio signals to form a sum, phase shift means for introducing predetermined phase shifts in at least all but one of said plurality of audio signals to form a plurality of phase differing signals, one for each of the audio signals, means for combining said phase differing signals to form a second signal component, said first and second signal components being equal to each other in amplitude and frequency but differing from each other in phase in accordance with said predetermined phase shifts, said first and second signal components being coupled to the two transmission channels, the phase differences between said phase differing signals being related to and uniquely characteristic of the respective angles between the directions from which sound represented by the corresponding audio signals is intended to be heard and a predetermined reference direction, said transmitter including an integral transducer unit comprising a first transducer arranged responsive to incident soundwaves to generate a first electrical signal and a second similar transducer arranged to generate a second electrical signal equal in amplitude and frequency to that generated by said first transducer but having a phase which differs from the phase of the signal generated by the first transducer by an amount dependent on the direction of incidence of said soundwaves.
Claim 2
Dependent Claim
263 words
A transmitter for a multi-channel sound reproduction system for generating a plurality of audio signals each corresponding to a respective audio source at a particular azimuth with respect to a reference point and having two transmission channels, comprising: means for forming a first signal component by adding together all the plurality of audio signals to form a sum, phase shift means for introducing predetermined phase shifts in at least all but one of said plurality of audio signals to form a plurality of phase differing signals, one for each of the audio signals, means for combining said phase differing signals to form a second signal component, said first and second signal components being equal to each other in amplitude and frequency but differing from each other in phase in accordance with said predetermined phase shifts, said first and second signal components being coupled to the two transmission channels, the phase differences between said phase differing signals being related to and uniquely characteristic of the respective angles between the directions from which sound represented by the corresponding audio signals is intended to be heard and a predetermined reference direction, said transmitter including an integral transducer unit comprising a first transducer arranged responsive to incident soundwaves to generate a first electrical signal and a second similar transducer arranged to generate a second electrical signal equal in amplitude and frequency to that generated by said first transducer but having a phase which differs from the phase of the signal generated by the first transducer by an amount dependent on the direction of incidence of said soundwaves.
Claim 3
Dependent Claim
88 words
A transmitter as claimed in claim 1, in which the first transducer comprises a microphone having an omni-directional response and the second transducer comprises a pair of microphones each having a figure-of-eight variation of sensitivity according to a cosine law, the two figure-of-eight patterns being oriented at right angles to one another in the horizontal plane, the output of said second and third microphones being connected to respective inputs of an adder via circuits adapted to produce a 90° difference between the phases of the output signals therefrom.
Claim 4
Dependent Claim
197 words
For use with a sound reproduction system wherein a receiver means couples audio data to at least three separate loudspeakers and wherein audio signals are transmitted to said receiver on only two channels, a transmitter comprising: means for generating audio signals from sound sources on a sound stage including at least three microphones disposed around the sound stage, coupling means for coupling said audio signals to the two transmission channels, said coupling means comprising a respective coder for each microphone having its input connected to the output of its associated microphone and adapted to supply to the transmission channels the first signal component having amplitude and frequency equal to that of the output of its associated microphone, each of said coders further including means for supplying to the transmission channels the second signal component having amplitude and frequency equal to that of the output of its associated microphone and having a predetermined phase relationship with the corresponding first signal component, the difference in phase between said corresponding first and second signal component corresponding to and being uniquely characteristic of the direction of the corresponding microphone from the center of the sound stage and a predetermined reference direction.
Claim 5
Dependent Claim
197 words
For use with a sound reproduction system wherein a receiver means couples audio data to at least three separate loudspeakers and wherein audio signals are transmitted to said receiver on only two channels, a transmitter comprising: means for generating audio signals from sound sources on a sound stage including at least three microphones disposed around the sound stage, coupling means for coupling said audio signals to the two transmission channels, said coupling means comprising a respective coder for each microphone having its input connected to the output of its associated microphone and adapted to supply to the transmission channels the first signal component having amplitude and frequency equal to that of the output of its associated microphone, each of said coders further including means for supplying to the transmission channels the second signal component having amplitude and frequency equal to that of the output of its associated microphone and having a predetermined phase relationship with the corresponding first signal component, the difference in phase between said corresponding first and second signal component corresponding to and being uniquely characteristic of the direction of the corresponding microphone from the center of the sound stage and a predetermined reference direction.
Claim 6
Dependent Claim
248 words
For use with a sound reproduction system wherein a receiver means couples audio data to at least three separate loudspeakers and wherein audio signals are transmitted to said receiver on only two channels, a transmitter comprising: means for generating audio signals from sound sources on a sound stage in which said means for generating audio signals includes an integral transducer unit comprising a first transducer arranged responsive to incident soundwaves to generate a first electrical signal and a second similar transducer arranged to generate a second electrical signal equal in amplitude and frequency to that generated by said first transducer but having a phase which differs from the phase of the signal generated by the first transducer by an amount dependent on the direction of incidence of said soundwaves, coupling means for coupling said audio signals to the two transmission channels, said coupling means including first means for combining the audio signals to form first signal components having amplitudes and frequencies corresponding to the amplitudes and frequencies of the audio signals, said coupling means further including second means for combining the audio signals to form second signal components having amplitudes and frequencies equal to the corresponding first signal components and having phase shifts with respect to the corresponding first signal components, the difference in phase between corresponding first and second signal components being uniquely characteristic of the angle between the direction of the corresponding sound source from the center of the sound stage and a predetermined reference direction.
Claim 7
Dependent Claim
248 words
For use with a sound reproduction system wherein a receiver means couples audio data to at least three separate loudspeakers and wherein audio signals are transmitted to said receiver on only two channels, a transmitter comprising: means for generating audio signals from sound sources on a sound stage in which said means for generating audio signals includes an integral transducer unit comprising a first transducer arranged responsive to incident soundwaves to generate a first electrical signal and a second similar transducer arranged to generate a second electrical signal equal in amplitude and frequency to that generated by said first transducer but having a phase which differs from the phase of the signal generated by the first transducer by an amount dependent on the direction of incidence of said soundwaves, coupling means for coupling said audio signals to the two transmission channels, said coupling means including first means for combining the audio signals to form first signal components having amplitudes and frequencies corresponding to the amplitudes and frequencies of the audio signals, said coupling means further including second means for combining the audio signals to form second signal components having amplitudes and frequencies equal to the corresponding first signal components and having phase shifts with respect to the corresponding first signal components, the difference in phase between corresponding first and second signal components being uniquely characteristic of the angle between the direction of the corresponding sound source from the center of the sound stage and a predetermined reference direction.
Claim 8
Dependent Claim
88 words
A transmitter as claimed in claim 4, in which the first transducer comprises a microphone having an omni-directional response and the second transducer comprises a pair of microphones each having a figure-of-eight variation of sensitivity according to a cosine law, the two figure-of-eight patterns being oriented at right angles to one another in the horizontal plane, the output of said second and third microphones being connected to respective inputs of an adder via circuits adapted to produce a 90° difference between the phases of the output signals therefrom.
References Cited (Backward Citations)
US3813494A
Cited
US3856992A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-02-17 | 1984-08-18 | 1985-02-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-02-17 | 1988-08-18 | 1989-02-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-02-17 | 1992-08-18 | 1993-02-17 | $7700.00 | Window Closed / Lapsed |