A boot (sometimes called an "audio boot") is a small sleeve that fits over the end of a BTE hearing aid to allow a different input signal from the normal hearing aid microphone(s).
The boot may have a wire and miniplug attached to it so that it can be plugged into some audio source like an ALD, a TV, Stereo, CD player, computer speakers or telephone. Alternatively, instead of a wire, some boots have a tiny FM receiver that picks up the signal via radio (this form is sometimes called an "FM boot").
The boot inserts the audio signal into the hearing aid's DAI interface. Some aids use three small golden contact points on the underside of the aid (just above the battery door); other aids have a proprietary set of contacts that the boot connects into.
Not all BTE hearing aids have a boot interface and boots don't even exist to fit some aids, so users who might benefit from assistive listening options should choose a hearing aid that supports DAI and boots.
Another alternative to a hearing aid's microphone as the input device is the loop (telecoil), which uses a magnetic signal rather than an electrical signal representing the sound.
A DAI or boot interface has some advantages over magnetic options:
On the other hand, wired DAI and boot interfaces do require a wire running up to each hearing aid (though FM boots avoid this problem).
- There is no EMI interference, since the input is electrical not magnetic.
- Since the signal is inserted electrically, it's strength is not affected by head position or orientation.