Adaptive filtering means for an automatic sound controlling apparatus

Claim 2

An automatic sound controlling apparatus comprising: an electric-signal-to-sound converter outputting a compensating sound to a canceling space to cancel a sound from a sound-producing source; a sound-to-electric-signal converter for converting a residual sound into an electric signal to form an error signal based on the residual sound; adaptive filtering means that controls filter coefficients based on the error signal from the sound-to-electric-signal converter to form a compensating signal that is supplied to the electric-signal-to-sound converter; transfer characteristics simulating means that simulates transfer characteristics and receives the compensating signal from the adaptive filtering means; adding means that adds the error signal and an output signal of the transfer characteristics simulating means; and a switch that alternatively feeds first and second signals to the adaptive filtering means, the first signal representing characteristics of the sound-producing source, and the second signal being an output of the adding means; wherein the switch feeds the first signal to the filtering means when the sound-producing source is in an unloaded state, and feeds the second signal to the filtering means when the sound-producing source is in a loaded state.

Claim 3

The apparatus of claim 1, further comprising a harmonic wave producing means that produces the first signal.

Claim 4

The apparatus of claim 2, wherein the switch feeds the first signal to the filtering means when the sound-producing source is in an unloaded state, and feeds the second signal to the filtering means when the sound-producing source is in a loaded state.

Claim 5

The apparatus of claim 2, wherein the sound-producing source comprises an engine, the first signal represents engine speed, the switch feeds the first signal to the filtering means when a value representing a change in engine speed is larger than a predetermined value, and the switch feeds the second signal to the filtering means when a value representing a change in engine speed is smaller than a predetermined value.

Claim 6

The apparatus of claim 4, wherein the switch feeds the second signal to the filtering means when a value representing a change in engine speed is equal to a predetermined value.

Claim 7

An automatic sound controlling apparatus comprising: an electric-signal-to-sound converter outputting a compensating sound to a canceling space to cancel a sound from a sound-producing source; a sound-to-electric-signal converter for converting a residual sound into an electric signal to form an error signal based on the residual sound; adaptive filtering means that controls filter coefficients based on the error signal from the sound-to-electric-signal converter to form a compensating signal that is supplied to the electric-signal-to-sound converter; transfer characteristics simulating means that simulates transfer characteristics and receives the compensating signal from the adaptive filtering means; adding means that adds the error signal and an output signal of the transfer characteristics simulating means; and a switch that alternatively feeds first and second signals to the adaptive filtering means, the first signal representing characteristics of the sound-producing source, and the second signal being an output of the adding means; wherein the sound-producing source comprises an engine, the first signal represents engine speed, the switch feeds the first signal to the filtering means when a value representing a change in engine speed is larger than a predetermined value, and the switch feeds the second signal to the filtering means when a value representing a change in engine speed is smaller than a predetermined value.

Claim 8

An automatic sound controlling apparatus comprising: an electric-signal-to-sound converter outputting a compensating sound to a canceling space to cancel a sound from a sound-producing source; a sound-to-electric-signal converter for converting a residual sound into an electric signal to form an error signal based on the residual sound; adaptive filtering means that controls filter coefficients based on the error signal from the sound-to-electric-signal converter to form a compensating signal that is supplied to the electric-signal-to-sound converter; transfer characteristics simulating means that simulates transfer characteristics and receives the compensating signal from the adaptive filtering means; adding means that adds the error signal and an output signal of the transfer characteristics simulating means; and a switch that alternatively feeds first and second signals to the adaptive filtering means, the first signal representing characteristics of the sound-producing source, and the second signal being an output of the adding means; wherein the sound-producing source comprises an engine, the first signal represents engine speed, the switch feeds the first signal to the filtering means when a value representing a change in engine speed is larger than a predetermined value, and the switch feeds the second signal to the filtering means when a value representing a change in engine speed is smaller than a predetermined value.

Claim 9

The apparatus of claim 6, wherein the switch feeds the second signal to the filtering means when a value representing a change in engine speed is equal to a predetermined value.