Adaptive active noise cancellation apparatus

Claim 2

An apparatus according to claim 1, characterized in that said correction system is constituted by an inverse filter (22) having an inverse function of the transfer function and arranged in an output signal path of said second sensor means (20).

Claim 3

An apparatus according to claim 1, characterized in that said correction system is constituted by a forward filter (24) having the transfer function and arranged in an output signal path of said first sensor means (14).

Claim 4

An adaptive active noise cancellation apparatus comprising: first sensor means (14) for detecting a sound generated by a sound source and outputting a detection signal; filter means (16), having a predetermined filter coefficient, for filtering the output signal from said first sensor means by using the predetermined filter coefficient, and outputting a filtered signal; sound generating means (17) for receiving the filtered signal and generating a sound corresponding to the filtered signal; an active noise cancellation control system (12) for actively canceling a source sound at a control target point by using the sound generated by said sound generating means; second sensor means (20), arranged at the control target point, for detecting a sound at the control target point and outputting a detection signal; and an adaptive control system (11) for receiving the output signals from said first and second sensor means and adaptively updating the filter coefficient in accordance with a state of a system for which noise cancellation is to performed by said active sound cancellation control system (12), characterized in that said adaptive control system (11) comprises: a correction system (18, 19, 21, 22) for correcting the output signal from said first sensor means (14) or said second sensor means (20) by using a transfer function corresponding to a delay in a spatial system between said sound generating means (17) and said second sensor means (20) and a delay required for calculation processing; error coefficient calculating means (23) for receiving the output signals which are output from said first and second sensor means (14, 20) and pass through said correction system, and obtaining a filter coefficient, as an error filter coefficient, which can set the output signal from said second sensor means to be zero while said active noise cancellation control system (12) executes a noise cancellation operation; and means (19) for obtaining a new filter coefficient from the error filter coefficient obtained by said error coefficient calculating means and a filter coefficient currently set in said active noise cancellation control system (12), and replacing the filter coefficient of said active noise cancellation control system with the new filter coefficient..

Claim 5

An apparatus according to claim 4, characterized in that said correction system is constituted by an inverse filter (22) having an inverse function of the transfer function and arranged in an output signal path of said second sensor means (20).

Claim 6

An apparatus according to claim 4, characterized in that said correction system is constituted by a forward filter (24) having the transfer function and arranged in an output signal path of said first sensor means (14).

Claim 7

An adaptive active noise cancellation apparatus comprising: first sensor means (114) for detecting a noise generated by a noise source and outputting a detection signal; filter means (115), having a predetermined filter coefficient, for filtering the output signal from said first sensor means by using the predetermined filter coefficient, and outputting a filtered signal; sound generating means (116) for receiving the filtered signal and generating a sound corresponding to the filtered signal; an active noise cancellation control system (112) for actively canceling a noise at a control target point by using the sound generated by said sound generating means; second sensor means (124), arranged at the control target point, for detecting a sound at the control target point and outputting a detection signal; and an adaptive control system (111) for receiving the output signals from said first and second sensor means and adaptively updating the filter coefficient in accordance with a state of a system for which noise cancellation is to performed by said active noise cancellation control system (112), characterized in that said adaptive control system comprises: first adaptive control means (121) for receiving the output signals from said first and second sensor means (114, 124) and obtaining a filter coefficient based on a difference between a filter coefficient currently set in said active noise cancellation control system and a new filter coefficient to be set in said active noise cancellation control system while said active noise cancellation control system (112) executes a noise cancellation operation, second adaptive control means (122) for receiving the output signals from said first and second sensor means and obtaining a filter coefficient based on a sum of a filter coefficient currently set in said active noise cancellation control system and a new filter coefficient to be set in said active noise cancellation control system while said active noise cancellation control system executes a noise cancellation operation; and update control means (123) for replacing the filter coefficient of said active noise cancellation control system with the new filter coefficient by using the filter coefficient based on the sum obtained by said second adaptive control means and the filter coefficient based on the difference obtained by said first adaptive control means.

Claim 8

An apparatus according to claim 7, characterized in that said first adaptive control means (121) comprises a first adaptive controller (126) for receiving the output signals from said first and second sensor means (114, 124), and a forward filter (125) having a filter coefficient corresponding to a transfer function between said sound generating means (116) and said second sensor means (124) and arranged in a signal path between said first sensor means (114) and said first adaptive controller (126), and said second adaptive control means (122) comprises a series circuit constituted by an amplifier (128) for amplifying an input signal twofold, a first forward filter (129) having a filter coefficient corresponding to a transfer function between said sound generating means (116) and said sensor means (124), and a second filter (130) having a filter coefficient equal to the filter coefficient set in said active noise cancellation control system, said series circuit causing the output signal from said first sensor means (114) to pass through said amplifier, said first forward filter, and said second filter in the order named, an adder (132) for adding the output signal, which is output from said first sensor means and passes through said series circuit, to the output signal from said second sensor means, a second adaptive controller (134) for receiving the output signal from said first sensor means and an output signal from said adder (132), and a third forward filter (133) having a filter coefficient corresponding to a transfer function between said sound generating means (116) and said second sensor means and arranged in a signal path between said second adaptive controller (134) and said first sensor means (114).

Claim 9

An apparatus according to claim 7, characterized in that said update control means (123) comprises a fourth filter (137) in which the filter coefficient based on the difference obtained by said first adaptive control means (121) is set and which filters the output signal from said first sensor means, a fifth filter (136) in which the filter coefficient based on the sum obtained by said second adaptive control means (122) is set and which filters the output signal from said first sensor means, an adder (138) for adding a signal filtered by said second filter (136) to a signal filtered by said first filter (137), a third adaptive controller (149) for receiving the output signal from said first sensor means and an output signal from said adder, an amplifier (139), arranged between said third adaptive controller and said first sensor means, for amplifying an input signal twofold, and means for transferring the filter coefficient obtained by said third adaptive controller, as the new filter coefficient, to said active sound cancellation control system.

Claim 10

An apparatus according to claim 7, characterized in that said update control means (123) comprises means (123a) for adding the filter coefficient based on the difference obtained by said first adaptive control means (121) to the filter coefficient based on the sum obtained by said second adaptive control means (122), and transferring a filter coefficient obtained by multiplying the sum filter coefficient by -(1/2), as the new filter coefficient, to said active sound cancellation control system (112).

Claim 11

An adaptive control apparatus comprising: adaptive control means (235) for setting and updating a filter coefficient such that an output signal becomes a desired signal; storage means (251) for storing a previous filter coefficient and a new filter coefficient obtained by the setting and updating of said adaptive control means; calculation means (253) for calculating one of a sum of the previous coefficient and the new coefficient and a difference therebetween; output means (257) for digitally filtering an input signal in accordance with a result obtained by said calculation means; bus line means (259, 263) coupling said memory means to each of said adaptive control means, said calculation means and said output means, for transferring the signal between said memory means and each of said adaptive control means, said calculation means and said output means; clock generating means (239) for generating a clock for setting an operation timing between said adaptive control means and said output means; and transfer function correcting means (233) for filtering the input signal, using a filter coefficient corresponding to a transfer function between an adaptive control evaluation point and a device to be adaptively controlled by said output signal.

Claim 12

An apparatus according to claim 11, characterized in that said storage means (251) comprises first storage means for storing the previous coefficient, and second storage means for storing the new filter coefficient obtained by the setting and updating of said adaptive control means, and said calculation means includes parallel operation processing means (290) for executing a parallel operation process between said first storage means and said second storage means.

Claim 13

An apparatus according to claim 11, characterized in that when said output means (257) outputs the output signal, using the filter coefficient obtained by said transfer function correcting means and said adaptive control means, the taps of said adaptive control means are divided into a plurality of units of taps, and the filter coefficients are outputted for each unit of tap in synchronism with the clocks generated from said clock generating means (239) and in accordance with the unit of tap.