Hearing loss is typically described as being conduc­tive, sensor­ine­ural, or mixed.

Refers to an impairment of one's ability to conduct airborne sound through the middle ear to the inner ear. Scar tissue or otoscl­erosis, the abnormal growth of bone within the middle ear, can lead to restricted movement of the ossicles. Recently it has been shown that there can also be conductive problems with the basilar membrane of the inner ear that reduce the efficiency of energy transfer to the hair cells (Holt).

Refers to impairment of the sensory unit consisting of the auditory nerve and the hair cells that excite it.

Sometimes the distin­ction between these two types of hearing loss can be made with a simple tuning fork test. If the tuning fork cannot be heard when sounded in air, then the base of the tuning fork is placed against the hard bone behind the ear. If the person can now hear it by conduction through the bone, then conductive hearing loss is indicated. It in cannot be heard by either air or bone conduc­tion, then sensor­ineural loss is indicated.

The "­power of ten" or logari­thmic nature of hearing response is evident in the fact that a loss in sensit­ivity by a factor of 10,000, or -40 decibels, is still at the edge of "­minimal loss". By the admittedly simplistic "rule of thumb" for loudness, this -40dB sound would still be 1/16 as loud as the 0 dB reference. 0 dB in this table represents the normal hearing threshold, or 0 dB Hearing Level. The categories of hearing loss are based on measur­ements at 500, 1000 and 2000 Hz.