Symmetrical filtering apparatus and method therefor

A method of filtering digital data comprising the steps of:

• (a) receiving filter control parameters at an input/output port;
• (b) upon receipt of the filter control parameters, calculating filter coefficients based upon the filter control parameters, wherein the filter coefficients, when applied to a single stage digital filter, produce a digital filtering function having a frequency response that is symmetric about a unity gain line;
• (c) receiving the filter coefficients and digitized input data at the single stage digital filter;
• (d) filtering the digitized input data using the single stage digital filter based upon the filter coefficients to produce filtered digitized data;
• and
• (e) outputting the filtered digitized data.

A graphic equalizer for selectively filtering audio data, the graphic equalizer comprising:

• a control panel, wherein the control panel receives filter control parameters from a user;
• a data buffer operably coupled to the control panel, wherein the data buffer receives the filter control parameters from the control panel;
• a bus operably coupled to the data buffer, wherein the bus passes the filter control parameters, instructions, and digitized audio data;
• an input/output port operably coupled to the bus, wherein the input/output port receives digitized audio data, and wherein the input/output port transmits filtered digitized audio data;
• a memory operably coupled to the bus, wherein the memory stores the filter control parameters, instructions, and digitized audio data;
• and
• a processor operably coupled to the memory, wherein the processor receives the filter control parameters and instructions from the memory, wherein the processor calculates filter coefficients based upon the filter control parameters, wherein the processor implements a single stage digital filter based upon the filter coefficients to filter the digitized audio data and to thereby produce the filtered digitized audio data, and wherein a frequency response of the digital filter is symmetric about a unity gain line.

A digital speaker telephone comprising:

• a microphone, wherein the microphone receives acoustic audio data and produces analog audio data;
• an A/D converter operably coupled to the microphone, wherein the A/D converter receives the analog audio data and converts the analog audio data to produce digitized audio data;
• an input/output buffer operably coupled to the A/D converter and a telephone system connection, wherein the input/output buffer receives digitized audio data and transmits filtered digitized audio data;
• and
• a graphic equalizer module operably coupled to the input/output buffer comprising:
• a controller, wherein the controller monitors the digitized audio data and produces filter control parameters based upon the digitized audio data;
• a bus operably coupled to the controller, wherein the bus passes filter control parameters, instructions, and digitized audio data;
• an input/output buffer operably coupled to the bus, wherein the input/output buffer receives filter control parameters and digitized audio data, and wherein the input/output buffer transmits filtered digitized audio data;
• a memory operably coupled to the bus, wherein the memory stores the filter control parameters, instructions, and digitized audio data;
• a processor operably coupled to the bus, wherein the processor receives the filter control parameters and instructions from the memory, wherein the processor calculates filter coefficients based upon the filter control parameters, wherein the processor implements a single stage digital filter based upon the filter coefficients to filter the digitized audio data and to thereby produce the filtered digitized audio data, and wherein a frequency response of the digital filter is symmetric about a unity gain line;
• a D/A converter operably coupled to the input/output buffer, wherein the D/A converter receives the filtered digitized audio data and converts the filtered digitized audio data to produce filtered analog audio data;
• and
• a speaker operably coupled to the D/A converter, wherein the speaker receives the filtered analog audio data and produces filtered acoustic audio data.