Dynamic bass boost apparatus and method

An audio processor comprising:

• a variable filter receiving an input signal and providing a filtered output signal, said variable filter having a quality factor that is controlled in response to a control signal, while a cutoff frequency of the variable filter remains fixed;
• a low-pass filter for selecting a band of the output signal;
• and
• a detector for detecting a signal level in the band selected by the low-pass filter and for generating the control signal in response to the detected signal level,
• wherein said variable filter further comprises a variable gain element responsive to the control signal and configured to amplify a bass frequency band of the input signal, and
• wherein a magnitude of the control signal is a function of an amplitude of the output signal within the selected band.

An audio processing method comprising the steps of:

• filtering an input signal in a variable filter and providing a filtered output signal, where the variable filter has a quality factor that is controlled in response to a control signal, while a cutoff frequency of the variable filter remains fixed;
• detecting a signal level representative of input signal level in a selected band to provide a detected signal level;
• and
• amplifying a bass frequency band of the input signal in response to the detected signal level.

An audio processor comprising:

• a state variable digital high-pass filter receiving an input data stream and providing a filtered output data stream, said digital filter having a quality factor that is controlled in response to a control variable, while a cutoff frequency of the variable filter remains fixed;
• a digital band select filter for selecting a band of the output data stream;
• and
• a detector algorithm for detecting a signal level in the band selected by the digital band select filter and for generating the control variable in response to the detected signal level,
• wherein the state variable digital high-pass filter includes a lookup table for establishin a desired relationship between the quality factor of the state variable digital high-pass filter and the detected signal level.

An audio processing method, comprising the steps of:

• filtering an input signal in a variable filter and providing a filtered output signal, wherein filtering the input signal comprises filtering an input data stream with a digital high-pass state variable filter and providing a filtered output data stream;
• detecting a signal level representative of input signal level in a selected band to provide a detected signal level;
• and
• controlling a quality factor of the variable filter in response to the detected signal level, wherein controlling the quality factor of the variable filter comprises accessing control values in a lookup table in response to the detected signal level.