Hearing aid compatible audio device with acoustic noise cancellation
A portable audio device, which includes active noise cancellation circuitry, a hearing aid compliant magnetic radiator, and a speaker/earpiece, is surrounded by ambient acoustic noise. The active noise cancellation circuitry provides an anti-noise signal at an input of the speaker to control/reduce the ambient acoustic noise outside of the device. In addition, the active noise cancellation circuitry provides an inverse anti-noise signal to an input of the magnetic radiator. The magnetic fields produced by the speaker driven by the anti-noise signal and the magnetic radiator driven by the inverse anti-noise signal cancel each other out through phase cancellation such that a hearing aid using a telecoil coupled to the audio device does not produce significant audio waves based on either of these signals. Other embodiments are also described.
1. An audio device, comprising:
a speaker having an input to receive an audio signal;
active noise cancellation (ANC) circuitry to provide an anti-noise signal at the input of the speaker to control ambient acoustic noise outside of the device and to cancel an effect of the anti-noise signal that is in the magnetic field produced by the speaker by generating a phase inversed anti-noise signal; and
a magnetic field radiator having an input to receive the phase inversed anti-noise signal.
2. The device of claim 1 , wherein the phase inversed anti-noise signal is generated by inverting the anti-noise signal so that the combined magnetic field produced by the speaker and the radiator, exhibits essentially none of the effects of the anti-noise signal.
3. The device of claim 1 , wherein the phased inversed anti-noise signal is an out-of-phase version of the anti-noise signal.
4. The device of claim 1 , further comprising:
one or more microphones to pick up the ambient acoustic noise outside of the device for use by the ANC circuitry.
5. The device of claim 1 , wherein the radiator is integrated with the speaker within a housing of the device.
6. The device of claim 1 , wherein the anti-noise signal is combined with the audio signal before being provided to the input of the speaker.
7. The device of claim 1 , wherein the phase inversed anti-noise signal is combined with the audio signal before being provided to the input of the radiator.
8. The device of claim 1 further comprising:
wireless network communications circuitry to produce the audio signal as a downlink audio signal; and
a downlink audio processor to enhance the downlink audio signal.
9. The device of claim 1 , wherein the device is a mobile phone and the speaker is an earpiece speaker for the mobile phone.
10. The device of claim 1 , further comprising:
mobile phone network communications circuitry to produce the audio signal as a downlink audio signal.
11. A method performed in an audio device, comprising:
receiving an audio signal;
generating a signal that represents background acoustic noise surrounding a user of the device;
generating an anti-noise signal intended to cancel the background acoustic noise;
generating a phase inversed anti-noise signal that is intended to undo an effect of the anti-noise signal;
converting the audio signal and the anti-noise signal into acoustic form while producing a first magnetic field; and
converting the phase inversed anti-noise signal into a second magnetic field.
12. The method of claim 11 , wherein the phase inversed anti-noise signal is generated by inverting the anti-noise signal by 180 degrees.
13. The method of claim 11 , wherein the phase inversed anti-noise signal is an out-of-phase version of the anti-noise signal such that the effect of the anti-noise signal in a magnetic field signal picked up by a T-coil of a hearing aid worn by the user, is negligible compared to an effect of the audio signal.
14. The method of claim 11 , wherein the signal representing the background acoustic noise surrounding the near-end user of the device is generated using a microphone of the device.
15. The method of claim 11 , further comprising combining the anti-noise signal with the audio signal in digital domain, prior to conversion into acoustic form.