Look How Far Hearing Aids Have Come Harvey Dillon Within this century, hearing aids have moved through five eras: from acoustic to carbon to vacuum-tube to transistor, and finally to digital. Technology is exploding in ways that provide substantial benefits to the user. Digitally programmable hearing instruments allow the fitter to finely tailor the response to suit the user, and allow the user to select a listening program that provides the best hearing in each of several acoustic environments. Multi-band wide dynamic range compression circuits allow the user to hear sounds with approximately their correct loudness in a wide range of situations, without needing to adjust the volume control. Dual microphones in BTE and ITE hearing instruments enable the user to focus listening in one direction when they need to, but avoid the disadvantages inherent in a directional hearing instrument at other times. Hand-held microphones allow a super focus that enable some hearing impaired people to hear better in noise than can a normally hearing person. Miniature wireless links allow this focussed signal to be beamed to a hearing instrument without the need for cables. They also allow signals that are largely free of noise and reverberation to be beamed directly to the hearing instrument from a talker some distance away. Fully digital hearing aids have the potential to do much more than they currently do, but already they can make more intelligent decisions about how much gain should be used in different frequency regions in different listening situations. They also enable feedback oscillation to be better managed, by never increasing gain sufficient to cause whistling, and by adaptively suppressing feedback. These advances made in the last few years enable more people to hear with better clarity and speech quality, in quiet and in noisy places, than has ever been possible. |