Bottom Up or Top Down?

William J. Campbell M.S.
Audiologist

The process of understanding speech in background noise can be thought of in terms of the sound entering the outer ear and traveling through the middle and inner ear where it is segregated into useful bits of information which eventually travel to the brain where  labels and meaning are attached.  Researchers  refer to this auditory trip as a bottom up approach due to its directional nature.  In addition, there is a parallel  process at work when  listening to speech mixed with other interfering speech or noise.  It is related to the ability of the brain to fill in the  gaps when only part of the message is available.   It relies on one’s thinking, working memory, attention, processing speed and language skills among other things.   In the audiology literature it is referred to as a top  down approach.   Hearing impairment distorts the  sound impressions we have been using over a lifetime.  Hearing aids can add important cues that have been lost due to the normal aging process.  However,  the ability to solve the riddle of a partially heard sentence in background noise will most certainly be related to an individual’s top down reserves.   One reason why the hearing aid industry continues to struggle with the ultimate device in  spite of all the wonderful digital capabilites is in part due to the large variability in the end users’  bottom up  and top down capabilities.

Suggested Reading

Journal of Acoustical Society of America, Vol. 121, #4, April 2007, pp 2362-2375
Journal of American Academy of Audiology, 19:533-541, 2008
Journal of Acoustical Society of America, Vol. 124, #6, December 2008, pp 3751-3771
Personal e-mail: Mounya Elhilali, Ph.D., Johns Hopkins University, 1/21/09
Journal of Acoustical Society of America, Vol.  126, #3, September 2009, pp 1427-1439
Journal of Acoustical Society of America, Vol. 127, #2, February 2010, pp 943-954; EL37—EL41
Journal of Acoustical Society of America, Vol., 127, #4, April 2010, pp 2509-2520