Communication device with active equalization and method therefor

• US 6,639,987 B2
• Filed: 12/11/2001
• Issued: 10/28/2003
• Est. Priority Date: 12/11/2001
• Status: Expired due to Fees

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: McIntosh, Jason Darrell
• Primary Examiner(s): Isen, Forester W.
• Assistant Examiner(s): Pendleton, Brian T.
• Application Number:
  US10/014,767
• Publication Number:
  US 20030108209A1
• Time in Patent Office: 686 Days
• Field of Search: 381/57, 381/71.6, 381/103, 455/550, 455/575, 455/569, 455/570, 455/90
• US Class Current: 381/71.6
• CPC Class Codes: H03G 5/005 of digital signals
• CPC Class Codes: H04R 2460/01 Hearing devices using active noise cancellation
• CPC Class Codes: H04R 2499/11 Transducers incorporated or for use in hand-held devices, e.g. mobile phones, PDA's, camera's
• CPC Class Codes: H04R 3/04 for correcting frequency response

Abstract

A communication device (10,110) includes an earpiece (14), a sensor (20), and an active equalization circuit (22). The earpiece (14) transmits an acoustic output signal (59) from the communication device (10,110). The sensor (10) is proximately located with the earpiece (14) and measures an acoustic pressure (61) at the earpiece (14) and generates a response signal (56). The active equalization circuit (22) is coupled to the sensor (20) and equalizes the acoustic output signal (59) using the response signal (56).

Claims

1. A communication device comprising:

an earpiece for transmitting an acoustic output signal from the communication device;

a sensor, wherein the sensor is proximately located with the earpiece, for measuring an acoustic pressure at the earpiece and generating a response signal; and

an active equalization circuit coupled to the sensor and receiving the response signal for equalizing the acoustic output signal at the earpiece, wherein the active equalization circuit comprises;

an audio processing block for receiving and processing a plurality of audio signals, thereby generating a digital input signal;

a digital signal processor coupled to the audio processing block for receiving and filtering the digital input signal, wherein the digital signal processor comprises;

an adjustable equalization filter, for filtering the digital input signal using a filter response, thereby generating a filtered audio signal, wherein the filter response is adjusted in response to an adjustment signal received from an adaptation circuit, and

the adaptation circuit coupled to the adjustable equalization filter and further coupled to the sensor, wherein the adaptation circuit uses the digital input signal and the response signal to generate the adjustment signal; and

an output audio processing block coupled to the digital signal processor for receiving and processing the filtered audio signal and sending the processed filtered audio signal to the earpiece.

2. A communication device as recited in claim 1 wherein the audio processing block comprises:

an audio input for receiving the plurality of audio signals, and

an amplifier coupled to the audio input for amplifying the plurality of audio signals, thereby generating a plurality of amplified audio signals, wherein the digital input signal is the plurality of amplified audio signals when the plurality of audio signals comprises a plurality of digital audio signals.

3. A communication device as recited in claim 2 wherein the audio processing block further comprises:

an analog to digital converter coupled to the amplifier for converting the plurality of amplified audio signals to the digital input signal.

4. A communication device as recited in claim 1 wherein the adaptation circuit includes noise compensation intelligence.

5. A communication device as recited in claim 1 wherein the output audio processing block includes:

a digital to analog converter for converting the filtered signal to an analog signal, and

an output amplifier coupled to the digital to analog converter for amplifying the analog signal received from the digital to analog converter.

6. A communication device as recited in claim 1 wherein the earpiece comprises a speaker coupled to the output audio processing block.

7. A communication device as recited in claim 1 further comprising:

a response signal-processing block coupled to the sensor for processing the response signal from the sensor, thereby generating a response data signal, wherein the adaptation circuit uses the digital input signal and the response data signal to generate the adjustment signal.

8. A communication device as recited in claim 7 wherein the response signal-processing block comprises:

a response amplifier for amplifying the response signal, and

a response analog to digital converter coupled to the response amplifier for converting the amplified response signal to the response data signal.

9. A communication device as recited in claim 1 further comprising:

a microphone for generating a talk signal; and

a summation block, wherein the summation block comprises;

a summer coupled to the microphone and coupled to the sensor, for adding the talk signal and the response signal, thereby generating a summation signal,

a shared analog to digital converter coupled to the summer for converting the summation signal to a digital summation signal, and

an echo canceller coupled to the shared analog to digital converter and further coupled to the audio processing block for separating the digital summation signal and generating a talk signal output and the response signal.

10. Within a communication device, a method of active equalization comprising:

fast fourier transforming a response data signal received from a sensor proximately located with an earpiece, thereby generating a transformed response data signal;

fast fourier transforming a digital input signal received from an audio processing block, thereby generating a transformed digital input signal;

dividing the transformed response data signal and the transformed digital input signal, thereby generating a divided signal;

estimating a transfer function using the divided signal;

averaging the transfer function thereby generating a frequency response;

smoothing the frequency response in a frequency domain using a moving average window;

inverting the smoothed frequency response;

inverse fast fourier transforming the inverted transfer function to generate a real valued impulse response;

equalizing the earpiece using a finite impulse response digital filter.

11. A method of active equalization as recited in claim 10 wherein in the equalizing step, the finite impulse response digital filter uses a weighted average of a plurality of response data signals.

12. A method of active equalization as recited in claim 10 further comprising:

prior to the inverse fast fourier transforming step, frequency shaping the inverted transfer function to attenuate a plurality of low frequencies and boost a plurality of high frequencies.