Digital hearing instruments take the continuous sound wave and break it up into very small, discrete bits of information. This is called digitizing the signal, and all digital hearing instruments do this. The more sophisticated digital hearing instruments are able to amplify the softest sounds of speech while at the same time subtracting out certain types of unwanted noises.
Digital signal processing allows hearing instrument designers to write computer programs called algorithms that can be customized to each individual’s hearing loss. In addition, digital hearing instruments enable important features—such as dual microphones and low battery warning signals—to be placed into a small in-the-ear device. It is this potential that makes digital hearing devices so promising for so many hearing losses. Selecting the type of hearing instrument that is right for the patient’s hearing loss and unique listening needs requires the guidance of a professional well versed in all variations of hearing instrument technology.
Digital hearing instruments use a microprocessor (computer) chip as the central component. A microphone is also used but amplification, shaping, and other signal modifications are achieved by representing the signal as a series of numbers. The numbers can be changed mathematically more quickly and precisely than an electronic analog signal–so the power of the hearing instrument is greatly enhanced. New digital hearing instruments can self-adjust for volume and frequency response (base, midrange, and treble), taking into account the individual’s hearing loss as well as difficult hearing environments. Digital hearing instruments self-adjust millions of times per second, which means the audio signal can be tailored with far greater flexibility, speed, and precision.