Hearing aids have many more “bells and whistles” than simple amplifiers. The FDA classified them as “wearable instruments” to compensate “impaired hearing”. Aids have, among many limitations, specific loudness limits in order to reduce risk from debilitating sound.
Similar-looking devices called “personal sound amplification products” (aka “PSAPs”) are not so-limited. Aids and PSAPs both may look alike with volume controls, t-switches, sound environment choices, etc., but today’s digital circuitry disguises many built-in controls.
A PA system consists of a microphone, an amplifier, a speaker, and a power source. In a hearing aid these same components carry names like “microphone” (sometimes with preamplifier), hearing aid “processor” (often including frequency emphasis augmenting system, filter system to cancel certain sounds, etc.), “earmold/eartip” to connect the aid’s “internal speaker” to user ear, and “battery” (either rechargeable or replaceable). With refinements in chip technology, typical battery life has grown longer as sound-enhancing capabilities of hearing aids have surpassed earlier generations of hearing instruments.
How Hearing Aids Out-Perform PASPs
Hearing aids make soft conversational sounds louder. Their loudness capabilities have a “cap,” so that sounds may only get louder to a point. Sounds emerging from the internal speaker can be made crisper for consonant clarity, or bass sounds can be enhanced to make music more enjoyable, often with the push of a button-operated wireless control. With today’s computer-mediated digital circuitry, proprietary circuits may make choices automatically. Wireless devices (e.g., remote bluetooth microphones, cellphone speakers, etc.) can bypass the aid’s microphone system to provide direct amplification, thus providing a clear auditory signal without confusing background noise.
The Brain Connection
Hearing instruments are a mechanism that connects what is going on in the environment to their users in real time. Ears are basically our human access system to our environment. Sound energy heard is converted to a form that can address our inner-ear hair cells. If those cells are damaged, today’s hearing aid technology allows alteration in that sound energy to a form that our damaged ears are able to process. If augmented sound energy gets to those hair cells, they in turn generate nerve energy that travels up the brainstem to the brain’s auditory processing centers. (If those hair cells are so badly damaged so that sound has no effect, there is still hope with the recent advent of cochlear implants, but that is another story.)
Finding the Definitive Hearing Aid
The FDA specifies how hearing aids are to be described. There is some latitude in terms of how internal components work and how they are controlled (e.g., via mini-screw potentiometers called “pots” or via computer manipulation of electronic pots accessible by a temporary umbilical from a PC to the actual hearing aid). Ears and hearing aids are both complex and it takes technology to wed the two. An audiologist, a hearing aid technician, a hearing instrument dispenser, etc. are able to identify an appropriate hearing aid for a candidate and adjust the instrument appropriately.