Method and apparatus for active sound control
AssigneeNational Research Development Corporation
InventorColin F. Ross
Life of this patent
Estimating the term…
Abstract
Sound control systems which employ sound cancellation may deteriorate due to ageing or change of conditions. The system described is contructed to change according to the sound level at a point where cancellation is to be achieved by sound from a loudspeaker driven by modified signals from a microphone which picks up sounds from a noise source. The signals from the microphone pass through a filter circuit having a transfer function which is controlled by a controller. Signals from the point where cancellation is required, and after modification, from the microphone and the filter circuit are employed by the controller to derive a control signal for the filter circuit.
Claims10
A sound control system comprising:
- first receiver means for generating first output signals representative of sound received at, or near, a first location where sound from a second location is to be cancelled,
- second receiver means for receiving signals at a third location and generating second output signals related to sounds at the second location,
- operational means including a computing section for operating on the second output signals according to a transfer function and generating input signals, and a transmission section for receiving said input signals and generating sounds at a fourth location, which when received at the first location, tend to cancel sound received from the second location at the first location, and
- a control means automatically adjusting the said transfer function, the control means being responsive to output signals of the first and second receiver means thereby optimizing cancellation of sound received from the second location at the first location.
A method of sound control for reducing noise in a first location due to a noise source in a second location, the method comprising:
- generating first and second output signals representative of sounds received at the first location and at a third location, respectively,
- operating on the said second output signals according to a transfer function to provide signals for generating sounds at a fourth location, the transfer function being such that sounds generated at the fourth location tend to cancel sound received from the second location at the first location, and
- automatically adjusting the said transfer function, the adjusting being responsive to the said first and second output signals thereby optimizing cancellation of sound received from the second location at the first location.
Dependencies are inferred from the claim text.