Hearing Aid Compression

William J. Campbell M.S., Audiologist

Compression refers to a hearing aid feature that attempts to increase the audibility of soft speech while preventing  loud sounds from becoming irritating or uncomfortable.  This technique can be accomplished very rapidly or very slowly .  Depending upon the speed of the electronic compression action, the hearing aid user sometimes notes improved intelligibility but not always.  Understanding of everyday conversation will hinge upon the condition of the inner ear.  Mild hearing loss implies less damage to cochlear frequency and loudness functions.  Therefore, multiple cues will be availabe for frequency and timing operations.  This patient population often understands speech quite well.  However, moderate to severe cochlear pathology reduces the ear’s ability to pick out fine pitch changes, making the ear more reliant on the peaks and valleys present in the timing of the sound envelope.  Compression that has rapid adjustments in turning on and off can add interference to this process, hence reducing intelligibility when background speech competes with the talker.   Circuits with slower adjustments or without compression can occasionally result in better user performance.  The choice of specific hearing aid features and their appropriate settings can make or break the patient’s eventual success.  Contact an audiologist with an appreciation of these circuit details and chances are you will hear life with better clarity.

Journal of Acoustical Society of America, vol. 121, #3, March 2007,  pp  1654  1664

Journal of Acoustical Society of America, Vol. 127, #6,June 2010, pp 3654-3665