Digital Hearing Aids
Digital hearing aids are programmed by a computer.   They use digital processing rather than analog.  This means they receive the sounds coming in from the microphone, digitize these sounds, send these numbers through a computer processor within the hearing aid, enhance them according to your prescription, and deliver the amplified sound to your ear.  With digital processing there is no distortion in the signal.  Additionally, the programming can be very tone-specific, allowing for a precise fit to the prescription.  Instead of just being able to adjust the “low tones” and the “high tones” (2 bands), they can be programmed for specific tones (5 to 20 bands) depending on the hearing aid. 

The aids are programmed in the office for their basic settings.  They then are capable of making decisions on how to amplify the sounds of the environment on their own.  They sample the sounds coming at them, thousands of times per second, and adjust their response based on this sampling.  If the aid detects noise it can lower the volume for the tones that are similar to the noise, without altering the volume for the speech tones. They can detect feedback (whistling or squealing noise coming from the hearing aid) and eliminate it.  They provide the cleanest signal with the most specific programming for the hearing needs of each ear.  Premium digitals now have different programs that the aid automatically selects based on what it “hears” in the environment.  Digital hearing aids are the most technically advanced hearing aids available.  The price range varies. 

Programmable Hearing Aids
Programmable hearing aids have microchips within them, allowing them to be adjusted and programmed using a computer rather than the manual adjustments of conventional aids.  Since the circuit can be adjusted via a microchip, some tone and volume adjustments are available.  They, however, have analog sound processors. They typically provide some comfort in noisy and loud environments, by softening loud sounds.  Some are capable of holding multiple programs.  These additional programs can be accessed by a pushbutton or switch on the hearing aid or by a remote control.  These hearing aids may have more than one microphone, to enhance speech in noisy situations.  They are priced at the same level as the basic entry level digitals.  Because they have fewer features they are not used much any more.

Conventional Hearing Aids
The circuitry used in conventional hearing aids is basic: a microphone, amplifier, and receiver.   They use analog technology.  They may not be able to soften loud sounds.  This can create some discomfort in noisier environments or in the event of a sudden loud sound (e.g. door slam, dog bark).  They can be manually adjusted at the time of the fitting to somewhat match your hearing loss prescription target.  A patient controlled manual volume adjusts volume.  They have no feedback suppression.  They are usually only used now with patients who have worn conventional aids for many years and like the way conventional aids sound.