Electrical audio signal processing systems and devices – Hearing protectors – electrical
Patent
1997-10-03
1999-11-16
Isen, Forester W.
Electrical audio signal processing systems and devices
Hearing protectors, electrical
381 716, 381 7112, 381 947, 381 717, A61F 1106, H03B 2900
Patent
active
059871440
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to active acoustic attenuation--that is to say, the operation that permits certain sounds to be attenuated by superimposing other sounds that are created in antiphase with the sounds to be attenuated.
The invention finds general application in the soundproofing of a space of chosen dimensions, and more particularly the space containing at least the head of a passenger sitting on a seat of a motorized vehicle such as an aircraft or an automobile with a view to improving the acoustic comfort of said passenger.
U.S. Pat. No. 5,133,017 (CAIN) proposes a seat equipped with a personal device for active acoustic attenuation which is integrated within the head-rest of the seat. The device comprises two channels disposed on the front face of the head-rest of the seat. Each channel possesses a loudspeaker linked to a ring of microphones. Electronic control means receive the noise picked up by the two rings of microphones and deliver, after processing, a control signal for noise attenuation for each loudspeaker in order to create sounds in antiphase with the noise to be attenuated.
The arrangement of the microphones in a ring here permits deterioration of the results to be avoided in the event of movements of the head of the individual or in the case of masking of a particular point of the ring by hair or such like. But this avoidance is obtained at the expense of a complexity of execution (due in particular to the number of microphones to be implemented) and the necessity to calculate the mean value of the noises picked up by each ring of microphones in order to improve the acoustic reproduction of the attenuation control signal.
The present invention provides a remedy for these drawbacks.
The invention focuses on a personal method for active acoustic attenuation comprising the following stages: signal in order to reduce an unwanted noise in response to a received control signal, as well as the sensor means in proximity to the head of an individual, active attenuation control signal for the source, source in order to determine at least the impulse response, during a predetermined period, between the output of the source and the input of the sensor means, and determined in accordance with a predetermined processing rule that is established at least in accordance with the impulse response as determined previously, in order to minimize the energy of the signal delivered by the sensor means.
According to a general definition of the invention, stage c) consists in converting said acoustic structure in order to maintain invariant, at least during the determination of the active attenuation control signal and in the presence of the individual, the volume within which the sensor means and the source are accommodated, permitting the impulse response between the output of the source and the input of the sensor means to be maintained invariant.
In this manner, owing to the invariance of the volume containing the sensor means and the source, and consequently the invariance of the impulse response between the output of the source and the input of the sensor means, the determination of the active acoustic attenuation signal has less need for processing.
Another aim of the present invention is a personal device for active acoustic attenuation in order to implement the method according to the invention, comprising: in order to reduce an unwanted noise in response to a received control signal, sensor means in proximity to the head of an individual, electrical signal to the input of the source in order to determine at least one impulse response, during a predetermined period, between the output of the source and the input of the sensor means and to determine, in real time, said active attenuation control signal in accordance with a predetermined processing rule that is established at least in accordance with the impulse response as determined previously, in order to minimize the energy of the signal delivered by the sensor means.
According to a general definition of the device according to the invention,
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Carme Christian
Roure Alain
Centre National de la Recherche Scientifique
Isen Forester W.
Mei Xu
Spencer George H.
Technofirst
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