What Does It Mean to Have “Normal” Hearing?

Definitions of normalcy are powerful determinations in medical fields and society more broadly. Although we use these definitions to determine if we have health problems, they are also used to categorize some people and their bodies as “abnormal” and in need of intervention. When it comes to hearing ability, the definition of normalcy has a fascinating history. This determination has roots that extend far back in time but remain pertinent today. Let’s learn more about how the definition of normal hearing came about, as well as the ways this definition continues to affect our understanding of hearing loss. 

 

The History of Normal Hearing

 

Hearing ability is categorized as normal with reference to “audiometric zero.” What does this mean in terms of sound? Audiometric zero is the level of a sound, specifically a pure tone in the form of a sine wave, that is barely detectible to a person with normal hearing. At any lower volume, a person with normal hearing will not be able to hear the sound. Yet, what exactly is normal hearing? The determination began at the 1933 World’s Fair in Chicago. At this event, also called “A Century of Progress International Exhibition,” hearing researchers engaged in an experimental measurement. 

 

They gathered participants from the World’s Fair to undergo a hearing test, and they determined how quiet a sound could be that would still be perceived by the majority of people in their sample. This ad hoc designation has remained remarkably powerful in the world of audiology and hearing sciences. Though human hearing environments and contexts have changed quite a bit from the time of the 1933 World’s Fair, this designation of normal hearing continues to be used to measure the degree of hearing loss for a given person at a given age. Specifically, a person who can hear sounds between 0 and 20 dBHL (Decibel Hearing Level) is now said to have normal hearing. 

 

The Definition of Hearing Loss

 

What qualifies a person for having hearing loss? Deviation from this definition of normal hearing is the key to understanding hearing loss, as well. Hearing loss is defined by the necessary volume a person requires to be able to hear something. If a sound is too quiet, below audiometric zero, a person with normal hearing ability will not be able to hear it. Yet, a person with hearing loss will require a sound to be louder to be perceived. The volume of this sound is used to determine the degree of hearing loss, and it is established through a specific hearing test called “pure tone audiometry.” 

 

In this test, a series of sounds at different frequencies, or pitches, and amplitudes, or volumes, are played for the person in the exam. Either through headphones or in a soundproof chamber, a person is asked to signal when a sound can be heard. They might raise their hand or push a button when the sound is perceptible. In the process of this exam, the examiner plays a sequence of frequencies and amplitudes to discover the threshold where sound can or cannot be heard. If a sound of a slightly quieter sound is played, the person in the test would not signal, and if it was just slightly louder, that person would signal to hear the sound. 

 

Hearing Loss and Treatment

 

Hearing loss is categorized in degrees of severity extending beyond that 0 to 20 dBHL level ranging from mild and moderate to severe and profound. People of different age groups tend to fall into different groups of hearing loss. Those under 60 years of age are likely to have normal hearing or mild hearing loss, but most people in their 70s have moderate hearing loss, and most people in their 80s have moderate to severe hearing loss. 

 

Although the normal hearing is a brute measurement determined with a non-random sample in 1933, it continues to be used to prescribe the right kind of treatment. Hearing aids are designed to amplify sounds into a range that can be perceived, and they provide that additional volume in ways that are unique to each individual wearer. If you are in need of treatment for hearing loss, the first step is to get a thorough diagnostic exam from one of our hearing health professionals.