Improvements in and relating to active sound attenuation
AssigneeSound Attenuators Limited
InventorsGeorge Brian Barrie Chaplin, Roderick Alan Smith
Life of this patent
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Abstract
A primary sound wave in a confined space is attenuated by a secondary sound wave generated to null with the primary wave. The secondary wave is produced by a first electrical signal representing the primary wave as sensed by a microphone, which is convolved with a second signal derived from the system impulse response as a program of operational steps. A second convolution process can cancel feedback of the secondary sound wave. Downstream residual noise is sensed by a second microphone which feeds a microprocessor which adjusts the convolution processes.
Claims10
Apparatus for achieving attenuation of a primary wave in a system by a specially generated secondary wave comprising first transducer means for deriving a first electrical signal representing, in a time-related manner, the primary wave to be attenuated, second tranducer means for generating the secondary wave from a second electrical signal, storage means in which a programme of time-related operational steps characterizing the system is contained and means for convolving the first electrical signal with the programme to produce the second electrical signal.
A method of attenuating sound in a defined space comprising deriving with a first transducer a first electrical signal representing, in a time-related manner, a primary sound wave which is to be attenuated and which is entering said space, and using said first electrical signal to derive a second electrical signal, said second electrical signal being used in a second transducer to generate a secondary wave in said space which will at least partially nullify the primary wave in said space, characterized in that the second electrical signal is derived from the first by convolving the first electrical signal with a programme of time-related operational steps which characterizes the first and second transducer and the acoustic path therebetween.
Dependencies are inferred from the claim text.