After twenty-nine years selling and fitting hearing aids I believe I have a fair idea of how today's hearing aids will perform in real life situations.  The following are my personal views on hearing, hearing aids, hearing aid design theory, acoustical physics, the human auditory system, modern theories on speech processing in the brain and how all of this interacts with the real world my patients want to communicate in with clarity. 

Please note that "CLARITY" is the keyword and not hearing.  People with hearing aids hear quite well, they hear motors, fans, traffic, plates and silverware, other people talking, they hear.  What they want is clarity and understanding to what they hear.  That is what the field of hearing aid dispensing and fitting should be all about, to often is not. 

What I would like to do is present some ideas about hearing aids and hearing that should help clarify what can be reasonably expected from well fit modern hearing aids.  It needs to be kept in mind that these ideas of mine are generalities and will vary from individual to individual as each hearing loss will be unique.  We build hearing aids to generalities and averages and we fit hearing aids to unique individuals.  I have never yet, in 29-years, fit a hearing aid to an average hearing loss. 

Two of the most often stated complaints about hearing aids involve range and confusion between hearing and effective communication.  The complaints are: I still can not hear my spouse when they are talking to me from the kitchen, and I still have to turn the television up louder than my spouse likes the volume.  To answer these two simple questions we must look at three seemingly unrelated areas; the laws of acoustical physics, the effects of hearing loss on range and hearing aid design parameters.  How these three interact together gives us the answer and it is anything but simple.

First is the range of human hearing and the effective range of communication. 
A normal hearing person has a range of hearing out to 30 foot radius.  This gives a pickup area of 2847 square feet.  In addition this pickup range is computed at a noise floor threshold of less than 40 dBA.  A noise floor of less than 40 dBA is very quiet.  Most modern mid-size to large cities have a greater than 40 dBA noise floor late at night and during the day generally have a noise floor of between 53 and 58 dBA on side streets.  Major streets average around 60 to 68 dBA with peaks up to 95-98 dBA.  Our office has an average noise floor of 44 to 50 dBA.  To give you some idea of noise levels we live in please review the following chart.  While a normal hearing person can hear at this range the ability to follow a normal conversation at this range is very limited.  Generally at 30 feet people yell at one another. 
A normal hearing person's effective range of communication is really much closer to 20 feet as can be seen in Figure 2.



The range of 20 feet limits the effective communication area to 1257 square feet.  Once we understand the range of normal hearing we can start to look at the range of hearing for people with hearing loss.