Direct Audio Input (DAI) is a feature of some BTE hearing aids which allows an external source to be directly connected as an input that bypasses the microphone.
For example, a television, telephone, computer, CD player, microphone, ALS or ALD to be directly input to the hearing aid.
DAI is not available on smaller, ITE, ITC, or CIC hearing aids.
The DAI interfaces with the the aid through a special connection, usually at the bottom end of the BTE. Some BTEs use a proprietary jack, and others use a "boot", like the one shown at the right, which slips over the end of the aid and electrically connects the source to the aid through three tiny brass dots on the underside of the BTE.
The DAI boot (or other connector) may use a wire and a mini-plug to plug into the audio source, or it may even have a tiny FM radio receiver attached to the boot with no wires required.
The signal is generally much improved because it goes directly into the hearing aid and bypasses the audio or magnetic interface that the hearing aid normally uses. Although some aids allow the aid's microphones to be simultaneously active with the DAI, most users find that the normal mode for DAI (aid's microphones disabled) works best, because it eliminates background noise.
Some hearing aids process the DAI input signal using the same circuits and programs that are used by the telecoil; other aids use a separate circuit and programs for DAI.