The difference between digital hearing aids, programmable hearing aids, and analog hearing aids rests partly on how the controls of these hearing aids are set by the Hearing Aid Professional.
For example, conventional analog hearing aid controls such as gain and output (power settings) are set manually using a screwdriver and no software is needed. With programmable and digital instruments, controls such as gain and output are typically manipulated via computer software. In general, this format provides for more consistent and accurate control of the hearing aid's different parameters and also allows for more flexibility.
Recently, however, new types of hearing aids have been introduced that have multiple characteristics. For example, some instruments are trimmer controlled. This allows for a digital product to be fit without a computer. However, all conventional hearing aids are manually controlled, digital hearing aids can be controlled manually or via computer software, and programmable aids are always manipulated via a computer or remote hand-held device.
Another way to differentiate conventional, programmable and digital instruments is in how they process sound.
Conventional analog hearing aids contain what we call analog signal processing. That is, there is no conversion of the incoming signal into numeric values (binary code) or digital format. The sound is processed as its original continuous waveform.
Digital hearing aids convert the incoming sound into a numeric language (binary code), and process sound within this format before converting the signal back to analog. The digital processing lends itself to even more flexibility and advanced features such as noise reduction algorithms and automatic/adaptive microphone directionality. Programmable hearing aids can be either digital or analog instruments.