Evok is a programmable hearing aid designed for use by individuals who are deaf or hard of hearing. It is available in receiver in canal, open ear, completely in canal, half shell/ canal, full shell, and behind the ear styles. All styles emphasize speech in challenging situations to make listening natural and comfortable. To improve understanding of speech in noise, the unit automatically switches to a directional microphone and simultaneously adjusts speech algorithms and comfort levels. Microprocessors automatically adjust for sudden changes to signal levels, such as soft and loud voices during the same conversation. The unit automatically reduces steady state noise such as a computer fan or humming from a refrigerator, as well as pseudo-random noise such as noise between the gaps in speech, and rapidly restores volume for soft speech when in the presence of loud sounds. An adaptive phase canceller prevents feedback. The unit can be fitted with up to five programs for different situations, such as noisy environments, telephone, television, music, or mute, and automatically switches to the appropriate mode. Some styles have waterproof microphone protection, and others position the microphone to make it less vulnerable to moisture. The unit also includes wax barriers, a moisture resistant coating on the internal circuitry. COLOR: Receiver in canal style comes in black, gray, or tan; open ear style comes in black, gray, tan, or white; completely in canal, half shell/canal, and full shell styles come in pink, tan, light brown, dark brown, red, or blue; behind the ear style comes in pink, tan, dark brown, green, red, or blue.