A digital signal synthesizer for generating a frequency and/or phase modified digital signal output comprises an input buffer, a transform module, a processing module, and an output buffer. The input buffer receives a digital input that is represented in a frequency domain representation. The transform module stores a fractional order control system that models a desired frequency and/or phase response defined by an assembly of at least one filter component. Each filter component is defined by a Laplace function that is modified to include a non-integer control order having a variable fractional scaling exponent. The processing module multiplies or divides the digital input with the fractional order control system stored in the transform module. Moreover, the output buffer stores a synthesized output of the input, which is modified in the frequency domain, the phase domain, or both according to the desired frequency and/or phase response by the processing module.

The present invention relates broadly to a method of digitally filtering a signal, such as an audio signal, using a digital filter. The digital filter includes a plurality of neighbouring sample points broken into zones having different frequency content or frequency ranges. The zones adjacent one another may have neighbouring sample points in common. Generally each zone has at least same distinct frequencies compared with other zones. That is, the zones are roughly dependent on the frequency content. The invention in its preferred form involves combining values for two or more of the neighbouring sample points for select of the zones depending on its frequency content. The values are combined so as to provide a modified zone having substantially the same number of sample points as the select zone. The modified zones together provide a modified filter to be applied to the signal.

A digital signal synthesizer for generating a frequency and/or phase modified digital signal output comprises an input buffer, a transform module, a processing module, and an output buffer. The input buffer receives a digital input that is represented in a frequency domain representation. The transform module stores a fractional order control system that models a desired frequency and/or phase response defined by an assembly of at least one filter component. Each filter component is defined by a Laplace function that is modified to include a non-integer control order having a variable fractional scaling exponent. The processing module multiplies or divides the digital input with the fractional order control system stored in the transform module. Moreover, the output buffer stores a synthesized output of the input, which is modified in the frequency domain, the phase domain, or both according to the desired frequency and/or phase response by the processing module.

A processing element for implementation in a digital signal processing system is provided. The processing element is configured to receive a first data stream comprising a plurality of digital values where each value represents a sample of an analog signal. The processing element is further configured to receive a second data stream comprising a series of digital values where each value represents a sample of the analog signal. The processing element is configured to filter the first data stream via a first Farrow-structured fractional delay (FD) filter and output a filtered first data stream; filter the second data stream via a second Farrow-structured FD filter and output a filtered second data stream; and temporarily store values from the second data stream and output the stored values to the first Farrow-structured FD filter so that the stored values can be used to filter the first data stream.

A method of designing a truncated filter includes designing a prototype filter with a target frequency response, and selecting a soft truncation function with a roll-off parameter specifying a rate in which the soft truncation function transitions to zero. The method also includes applying the soft truncation function to the prototype filter to produce a truncated filter, and storing the truncated filter to a memory.

In some aspects, a transducer of a system may convert an input to an analog signal. An analog-to-digital converter of the system may convert the analog signal to a digital signal. A low-pass filter of the system may filter the digital signal to create a filtered digital signal. The filtering of the digital signal reduces noise near a resonance frequency of the transducer. Numerous other aspects are described.