Audio system with integral hearing test

1. A circuit, comprising:

a plurality of variable gain amplifiers (VGAs) coupled to receive an audio signal;

a switch to select the audio signal from a plurality of sources in a normal mode;

a plurality of filters, each filter coupled to a respective VGA and configured to filter an output signal from the respective VGA; and

a processor coupled to the VGAs and configured to apply a respective audio frequency to each VGA in a test mode to determine a respective Pain for each VGA based on user input

and to apply the respective gain to each VGA in the normal mode.

2. The circuit of claim 1 , comprising a clock circuit configured to apply the respective audio frequency to each VGA in the test mode.

3. The circuit of claim 1 , wherein the processor is configured to control the respective gain of each VGA in the test mode.

4. The circuit of claim 1 , wherein the respective audio frequency of each VGA is filtered by the respective filter coupled to the VGA in the test mode.

5. The circuit of claim 1 , comprising:

a sum circuit coupled to receive the filtered output signal from each filter and produce a sum signal; and

an output VGA coupled to receive the sum signal and produce an output signal.

6. The circuit of claim 1 , wherein the audio signal is produced during the normal mode by at least one of a portable electronic device, a telephone handset, and a microphone.

7. The circuit of claim 1 , comprising a wireless receiver configured to produce the audio signal.

8. A method of operating a circuit, comprising:

applying a first audio frequency to a first band-specific circuit in a test mode of operation;

incrementing a first gain of the first band-specific circuit by a processor until a user input is received;

displaying the first audio frequency and the first gain;

storing the first gain in a nonvolatile memory of the processor in response to the user input; and

applying the first gain to the first band-specific circuit by the processor during a normal mode of operation.

9. The method of claim 8 , comprising:

applying a plurality of audio frequencies to a respective plurality of band-specific circuits in the test mode of operation after the step of applying a first audio frequency;

incrementing a gain of each of the plurality of band-specific circuits by a processor until a respective user input is received;

displaying the plurality of audio frequencies and their respective gains;

storing each respective gain in the nonvolatile memory of the processor in response to the respective user input; and

applying each respective gain to each of the plurality of band-specific circuits by the processor during a normal mode of operation.

10. The method of claim 8 , comprising:

applying an input signal from a portable electronic device to the first band-specific circuit in the normal mode of operation;

amplifying the input signal by the first band-specific circuit at the first gain;

filtering the input signal by the first band specific circuit; and

producing the amplified and filtered input signal at a hearing transducer.

11. The method of claim 8 , comprising:

applying an input signal from a telephone handset to the first band-specific circuit in the normal mode of operation;

amplifying the input signal by the first band-specific circuit at the first gain;

filtering the input signal by the first band specific circuit; and

producing the amplified and filtered input signal at a hearing transducer of the telephone handset.

12. The method of claim 8 , comprising:

applying an input signal from a microphone to the first band-specific circuit in the normal mode of operation;

amplifying the input signal by the first band-specific circuit at the first gain;

filtering the input signal by the first band specific circuit; and

producing the amplified and filtered input signal at a hearing transducer.

13. The method of claim 8 , comprising:

applying an input signal from a wireless receiver to the first band-specific circuit in the normal mode of operation;

amplifying the input signal by the first band-specific circuit at the first gain;

filtering the input signal by the first band specific circuit; and

producing the amplified and filtered input signal at a hearing transducer.

14. The method of claim 8 , comprising:

displaying a hearing threshold of the user in response to the user input; and

displaying the first gain in response to the test mode of operation.

15. A circuit, comprising:

a plurality of band-specific circuits coupled to receive a respective audio frequency in a test mode and produce a respective band-specific output signal;

a processor configured to store a gain of each respective band-specific output signal in response to a respective user input signal;

a switch to select an audio signal from a plurality of sources in a normal mode; and

an input circuit configured to apply the audio signal to each band-specific circuit during the normal mode, wherein each band-specific circuit produces a respective normal mode output signal having the respective stored gain.

16. The circuit of claim 15 , wherein the plurality of band-specific circuits comprises a digital signal processor.

17. The circuit of claim 15 , wherein the plurality of band-specific circuits comprises at least one of a BiQuad filter, a finite impulse response (FIR) filter, and an infinite impulse response (IIR) filter.

18. The circuit of claim 15 , wherein at least one of the band-specific circuits comprises a low pass filter, and wherein at least another of the band specific circuits comprises a high pass filter.

19. The circuit of claim 15 , configured to receive the signal applied to each band-specific circuit during the normal mode from at least one of a portable electronic device, a telephone handset, a microphone, and a wireless receiver.

20. The circuit of claim 15 , comprising:

a display configured to display the gain and audio frequency of the band-specific output signal; and

a switch circuit configured to select the gain and audio frequency of the band-specific output signal.