These microphones pick up sounds coming from in front of you better than coming from behind or beside you, improving your ability to hear when you're in an environment with a lot of background noise. Many hearing aids have both a regular and a directional microphone, and automatically switch between the regular and directional modes.
This technology, also referred to as telecoil T switches, makes it easier to hear when talking on the telephone. The telecoil eliminates the sounds from your environment and only picks up the sounds from the telephone. Some hearing aids switch automatically when the phone is held up to the hearing aid, while others require flipping a switch. Keep in mind that this technology works only with telephones that are compatible with hearing aids - most cell phones are.
New hearing aids can transmit sound from Bluetooth devices, such as Bluetooth cell phones. These hearing aids require an interface that wirelessly picks up the Bluetooth signal from Bluetooth compatible devices and transmits the signal to the hearing aid.
Some hearing aids use a remote control that makes volume control adjustments or other changes without touching the hearing aid. The remote may also make other adjustments, such as activating the directional microphone or increasing the noise reduction.