A Behind-the-ear, hearing aid, being larger in size, allows for more gain(power) than a Custom made Hearing Aids. Physical size,room considerations, dictate what electronic components can be installed inside either the custom made shell, or the case of the BTE hearing aid. The Behind-the-ear hearing aid usually uses a size 675 battery (blue tab) because it provides longer battery life than any other size. Usually People that need the power of a BTE need a battery that provides the longer battery life, otherwise they would be changing batteries every other day. The more severe the hearing loss, the bigger the hearing aid, the bigger the battery drain, the bigger the battery used in the manufacture of the hearing aid.The biggest potential for hearing aid users are those that suffer from what is called a "High Frequency" hearing loss. Those People have normal hearing in the low frequencies, but have a loss in what is considered the high frequencies in audiology.
These devices fit in the outer ear bowl (called the concha); they are sometimes visible when standing face to face with someone. ITE hearing aids are custom made to fit each individual's ear. They can be used in mild to some severe hearing losses. Feedback, a squealing/whistling caused by sound leaking and being amplified again, may be a problem for severe hearing losses.[citation needed] Some modern circuits and Disability Products are able to provide feedback regulation or cancellation to assist with this. Another way to deal with feedback is venting. The vent is a tube primarily placed to offer pressure equalization. However, different vent styles and sizes can be used to influence and prevent feedback . ITEs have not been recommended for young children because their fit could not be as easily modified as the earmold for a BTE, and thus the aid had to be replaced frequently as the child grew.[citation needed] However, there are new ITEs made from a silicone type material that mitigates the need for costly replacements.
