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This section contains information on hearing loss from an audiological perspective. For information on people who are Deaf from a cultural perspective, go to Understanding Deaf Culture.

What is Hearing?

Hearing is the ability of the ears to pick up sounds and translate them into a form that the brain can process and understand. Unlike the other senses which may rely on a chemical reaction, hearing is a totally mechanical process relying on the movement of small bones in the ear canal in conjunction with nerve endings that translate the movement into sound.

What is Hearing Loss?

A hearing impairment is a condition that limits a person’s ability to receive sounds in all or most of its forms. It is a spectrum ranging from total deafness (when capitalized as Deafness, it denotes cultural deafness) to any level of hearing loss. It can be congenital or acquired. Most people experience some loss of hearing acuity as they age.

It is useful to know that sound is measured by its loudness or intensity (measured in units called decibels, dB) and its frequency or pitch (measured in units called hertz, Hz). Impairments in hearing can occur in either or both areas, and may exist in only one ear or in both ears. Hearing loss is generally described as slight, mild, moderate, severe, or profound, depending upon how well a person can hear the intensities or frequencies most greatly associated with speech. For more information see the Four Types of Hearing Loss.

Who Is Affected

Anyone can acquire a hearing limitation. As one ages it is almost inevitable. It can be an insidious process that slowly erodes an individual’s confidence and isolates them before they realize what is happening. In children it will have an effect on their acquisition of language skills and, potentially, social skills. In adults it can have effects on social life, on job performance and upon family life. Dealing with acquired hearing loss and choosing to use hearing aids can be a long process before reaching a satisfactory benefit. For some, the process of assimilating a new identity as a person with a hearing loss may take many years and never be completed.

The Gallaudet Research Institute reports: 1

  • More than 28M people (10%) report having "a little trouble" hearing and more than half of those people are 45 or over.
  • About 6M people (2.2%) report having "a lot of trouble" hearing and more than half of those are 45 or over.
  • Approximately 600,000 people in the US (0.22% of the population) are deaf and more than half are 65 or over.
  • Most people who suffer chronic Tinnitus hear noise in their ears all the time. This can cause lack of sleep, impaired concentration and remembering and even suicidal thoughts. Along with loud noise another cause of tinnitus is head and neck injury. It is estimated that one in ten people who have had a head or neck injury have residual tinnitus.

A Brief Summary of Estimates for the Size of the Deaf Population in the USA Based on Available Federal Data and Published Research (from the Gallaudet Research Institute):

  • About 2 to 4 of every 1,000 people in the United States are "functionally deaf," though more than half became deaf relatively late in life; fewer than 1 out of every 1,000 people in the United States became deaf before 18 years of age.
  • However, if people with a severe hearing impairment are included with those who are deaf, then the number is 4 to 10 times higher. That is, anywhere from 9 to 22 out of every 1,000 people have a severe hearing impairment or are deaf. Again, at least half of these people reported their hearing loss after 64 years of age.
  • Finally, if everyone who has any kind of "trouble" with their hearing is included then anywhere from 37 to 140 out of every 1,000 people in the United States have some kind of hearing loss, with a large share being at least 65 years old.

Socio-linguistic or Culturally Deaf

For some time, it has been increasingly common to distinguish between those who are deaf and those who are "Deaf." The capitalization indicates sociolinguistic affiliation in addition to audiological distinction. No major federal survey activity inquires about special language use or social identification among those who are deaf (or hard of hearing). That is, there are no questions about American Sign Language (ASL) or any other signed language used on federal surveys. Nor are there questions about cultural identity among people who are Deaf.

The only study that helps to answer this question was done over 30 years ago (before IDEA, ADA, Section 504 of the Rehabilitation Act, et cetera). Based upon this old survey (part of a project known as the National Census of the Deaf Population [NCDP]), it was estimated that there may have been 500,000 people who signed at home in 1972 (about 0.25% of the population), only slightly more than half of whom were deaf (280,000 or 0.14% of the population). In other words, in 1972, a little more than 1 of every 1,000 people in the United States was a deaf person who reported s/he was a "good" signer.

However, if we were to take a more liberal view of who would have counted as an ASL user among those responding to the National Census of the Deaf Population (NCDP) then, of course, our numerical estimates would be higher. That is, including those NCDP respondents who identified themselves as “fair” or “poor” signers results in an estimated 642,000 persons who signed at home in 1972, more than half of whom were deaf (375,000 or 0.19% of the population). 2

Looking at the Impacts

Hearing loss prevents an individual from receiving sound in all or most of its forms.  Key functions that can be impacted by hearing loss include:

  • Hearing speech, including for some, the ability to differentiate speech within other sounds
  • Hearing emergency or informational notifications and recordings
  • Hearing abrupt changes in the physical environment, such as a fast car when crossing a street

Functioning with Hearing Loss

How one functions with hearing loss relates to a number of physiological, personal, and environmental factors. Examples of the impact of physiological, personal and environmental factors include:

  • Cognitive limitations affect how well a person processes multiple environmental cues.
  • The ability to speech-read does not correlate with intelligence.
  • A person with hearing loss must guess the content of speech (both words and meaning). It is accomplished by interpreting a set of imprecise cues. Researchers estimate that only about 40% of the sounds of normal speech are clearly visible on the lips.
  • Since sight is often a key tool for information and communication for people with hearing impairments, visual limitations diminish one’s ability to detect cues.
  • People with hearing loss who perform well on hearing tests but cannot speech-read well may understand people less than someone who performs poorly on hearing tests but can speech-read well. In conversation, a person can be severely disabled even if they do not perform poorly on hearing tests.
  • Chronic Tinnitus means hearing noise in their ears all the time. This can cause distraction, impaired concentration and remembering, lack of sleep, and even suicidal thoughts.

1Gallaudet Research Institute, 9.22.05


2Mitchell, Ross E., Travas A. Young, Bellamie Bachleda, and Michael A. Karchmer. 2006, in press. How Many People Use ASL in the United States? Why Estimates Need Updating. Sign Language Studies, Vol. 6, No. 3.