Apple wants its iPhone to work better with hearing aids. The company has been granted a patent (number 9,672,804) for a “hearing aid compatible audio device with acoustic noise cancellation.”
In the patent filing, Apple notes that hearing aids operate in either a microphone (acoustic) mode or a telecoil (inductive) mode. In the microphone mode, sound waves that are incident upon a microphone which is integrated in the hearing aid are converted into an electrical audio signal. In the telecoil mode, an induction coil (also referred to as a telecoil or T-coil), which may also be inside the hearing aid, picks up the local magnetic field that has been modulated by the receiver or a dedicated coil of a nearby telephone handset.
In telecoil mode, hearing aids typically turn-off their internal microphone and only receive audio that has been modulated by the receiver of a nearby telephone handset. Accordingly, the hearing impaired user would not be able to hear the ambient acoustic noise at the baseball game as the hearing aid is not picking up the ambient acoustic noise.
This means that the audio cancellation signal that is played to the user through a speaker/earpiece of the hearing aid would provide noise or interference to the hearing impaired user since there is no perceived ambient acoustic noise for the audio cancellation signal to reduce or negate. Apple says there’s a need for an audio device that reduces interference caused by active noise cancellation circuitry picked-up by as hearing aid that is electromagnetically coupled to the audio device.
Here’s Apple’s summary of the invention: “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.”
Of course, Apple files for — and is granted — lots of patents by the U.S. Patent & Trademark Office. Many are for inventions that never see the light of day. However, you never can tell which ones will materialize in a real product.