An interference sound suppressing device includes: an input signal acquiring part that acquires an input signal obtained from a microphone; a reference signal acquiring part that acquires a reference signal; a data inserting part that increases an amount of data of the input signal to be larger than an amount of data of the reference signal by inserting a plurality of zeros into the input signal; an interference sound suppressing part that suppresses an interference sound component included in the input signal by using the input signal having the amount of data increased and the reference signal; a data deleting part that restores the amount of data of the input signal to an original amount by deleting the plurality of zeros inserted from the input signal in which the interference sound component is suppressed; and an output part that outputs the input signal having the amount of data restored.

A noise cancellation system, comprising: an input for a digital signal, the digital signal having a first sample rate; a digital filter, connected to the input to receive the digital signal; a decimator, connected to the input to receive the digital signal and to generate a decimated signal at a second sample rate lower than the first sample rate; and a processor. The processor comprises: an emulation of the digital filter, connected to receive the decimated signal and to generate an emulated filter output; and a control circuit, for generating a control signal on the basis of the emulated filter output. The control signal is applied to the digital filter to control a filter characteristic thereof.

A noise cancellation system, comprising: an input for a digital signal, the digital signal having a first sample rate; a digital filter, connected to the input to receive the digital signal; a decimator, connected to the input to receive the digital signal and to generate a decimated signal at a second sample rate lower than the first sample rate; and a processor. The processor comprises: an emulation of the digital filter, connected to receive the decimated signal and to generate an emulated filter output; and a control circuit, for generating a control signal on the basis of the emulated filter output. The control signal is applied to the digital filter to control a filter characteristic thereof.

A noise cancellation system, comprising: an input for a digital signal, the digital signal having a first sample rate; a digital filter, connected to the input to receive the digital signal; a decimator, connected to the input to receive the digital signal and to generate a decimated signal at a second sample rate lower than the first sample rate; and a processor. The processor comprises: an emulation of the digital filter, connected to receive the decimated signal and to generate an emulated filter output; and a control circuit, for generating a control signal on the basis of the emulated filter output. The control signal is applied to the digital filter to control a filter characteristic thereof.

A personal audio device, such as a wireless telephone, includes an adaptive noise canceling (ANC) circuit that adaptively generates an anti-noise signal from a reference microphone signal that measures the ambient audio and an error microphone signal that measures the output of an output transducer plus any ambient audio at that location and injects the anti-noise signal at the transducer output to cause cancellation of ambient audio sounds. A processing circuit uses the reference and error microphone to generate the anti-noise signal, which can be generated by an adaptive filter operating at a multiple of the ANC coefficient update rate. Downlink audio can be combined with the high data rate anti-noise signal by interpolation. High-pass filters in the control paths reduce DC offset in the ANC circuits, and ANC coefficient adaptation can be halted when downlink audio is not detected.

A vehicle includes a music signal processing system having a loudspeaker disposed within a passenger compartment of the vehicle and emitting audible music into the passenger compartment. A microphone is disposed within the passenger compartment and converts the audible music and noise within the passenger compartment into an analog electrical microphone signal. An analog-to-digital converter is connected to an output of the microphone and receives the analog electrical microphone signal and converts the analog electrical microphone signal into a digital electrical microphone signal. A sample rate down converter is connected to an output of the analog-to-digital converter. A narrow band adaptive noise control is connected to an output of the sample rate down converter and receives an engine speed signal. A sample rate up converter is connected to an output of the narrow band adaptive noise control. An adder device adds an output of the sample rate up converter to a music signal. A digital-to-analog converter is connected to an output of the adder device. An amplifier has an input connected to an output of the digital-to-analog converter. An output of the amplifier is connected to an input of the loudspeaker.

A noise cancellation system, comprising: an input for a digital signal, the digital signal having a first sample rate; a digital filter, connected to the input to receive the digital signal; a decimator, connected to the input to receive the digital signal and to generate a decimated signal at a second sample rate lower than the first sample rate; and a processor. The processor comprises: an emulation of the digital filter, connected to receive the decimated signal and to generate an emulated filter output; and a control circuit, for generating a control signal on the basis of the emulated filter output. The control signal is applied to the digital filter to control a filter characteristic thereof.

A digital circuit arrangement for an ambient noise-reduction system affording a higher degree of noise reduction than has hitherto been possible. The arrangement converts the analog signals into N-bit digital signals at sample rate f.sub.0, and then subjects the converted signals to digital filtering. The value of N in some embodiments is 1 but, in any event, is no greater than 8, and f.sub.0 may be 64 times the Nyquist sampling rate but, in any event, is substantially greater than the Nyquist sampling rate. This permits digital processing to be used without incurring group delay problems that rule out the use of conventional digital processing in this context. Furthermore, adjustment of the group delay can readily be achieved, in units of a fraction of a micro-second, providing the ability to fine tune the group delay for feed forward applications.

There is provided a signal processing device s including a noise cancellation process clock generation unit configured to generate a noise cancellation process clock having a predetermined fixed frequency, a noise canceling unit configured to include a noise canceling filter operating based on the noise cancellation process clock and generating a noise canceling signal having a signal property of canceling an external noise component based on an input audio signal including the external noise component picked up by a microphone, and an addition unit superimposing the noise canceling signal generated by the filter on a digital audio signal, and a sampling rate conversion unit configured to rate-convert the input digital audio signal sampled at a clock in asynchrony with the noise cancellation process clock to a signal at a sampling frequency in synchrony with the noise cancellation process clock and to supply the rate-converted signal to the addition unit.

An audio system having low latency includes a digital audio processor as well as sensor inputs coupled to the processor. The sensor inputs may be microphone inputs. The audio processor operates at the same frequency as the sensor inputs, which is typically much higher than an audio signal provided to the audio processor. In some aspects the audio processor operates as a noise cancellation processor and does not include an audio input.