According to the National Institute of Health (NIH), approximately 15% of American adults (37.5 million) aged 18 and over report some trouble hearing, about one in three people in the U.S. between the ages of 65 and 74 has hearing loss, and nearly half of Americans aged 75 and older have difficulty hearing. Audiometry tests therefore show that it is extremely common to lose our hearing as we get older. ASA/ANSI S3.6-2018 (R2023): Specification For Audiometers provides specifications and tolerances for pure tone, speech, and masking signals for audiometers, ensuring these hearing tests results are accurate and consistent.
What Is An Audiometer?
An audiometer is an electrical medical device used to test hearing acuity in humans. It measures a person’s ability to hear different sounds, pitches, or frequencies. Audiometers can be used for several different types of hearing tests. They are classified as a medical diagnostic device under the ear, nose, and throat category. Its parts include a sound generator, oscillator, attenuator, microphone, and earphone.
In the American National Standard, ASA/ANSI S3.6-2018 (R2023), various types of audiometers are defined:
- Extended high frequency audiometer: A pure-tone audiometer providing test frequencies in the 8000 to 16000 Hz range
- Békésy or automatic recording audiometer: A pure-tone audiometer in which the frequency, repetition rate, and rate of change in amplitude of the signal are automatically controlled, but in which the direction of change in signal level, whether increasing or decreasing, is under control of the subject whose responses are recorded automatically
- Manual audiometer: A pure-tone audiometer in which the signal presentations, frequency, hearing level selection, and recording the results are performed manually
- Computer-controlled audiometer: An audiometer which the test procedure is controlled by means of a computer
- Speech audiometer: An audiometer which facilitates the use of either live or recorded speech or speech-like signals for measurement of hearing
The ASA/ANSI S3.6-2018 (R2023) Standard for Audiometers
The audiometers covered in ASA/ANSI S3.6-2018 (R2023) determine the hearing threshold level of an individual in comparison with a chosen standard reference threshold level. This standard provides specifications and tolerances for pure tone, speech, and masking signals, as well as reference threshold levels for audiometric transducers like supra-aural, circumaural, insert earphones, bone vibrators, and loudspeakers. The standard also describes the minimum test capabilities of different types of audiometers.
ASA/ANSI S3.6-2018 (R2023) ensures that tests of hearing, and particularly tests of hearing threshold, performed on the same individual with different audiometers give equivalent results when used under comparable test conditions. Further, the test results should accurately and validly represent the level difference, if any, that may exist between the threshold of the individual tested and the reference threshold of hearing. This standard covers the general specifications for audiometers that require behavioral responses from a listener, as well as specific requirements governing the functional units of audiometric equipment such as type or types of signal, signal level control mechanisms, and types of transducers.
Instruments that are not audiometers but are used primarily for audiometric testing purposes that incorporate calibrated sound sources (e.g., acoustic immittance systems, otoacoustic emission systems, or narrowband noise generators), should whenever possible, conform to clauses 4 through 10 of this standard.
What Are the Types of Audiometry?
There are many types of audiometry tests. Here are some of the more common tests:
Pure Tone Audiometry
This test involves wearing a set of headphones connected to an audiometer. As you wear the headphones, pure tones are sent to your ears and each ear gets tested individually. The tones vary in frequency/pitch and are measured in hertz (Hz), and intensity/loudness are measured in decibels (dB). During the test, the patient is instructed to raise their hand, press a button, or signal when they hear a tone. The results of the test are placed on a graph—an audiogram—along with the minimum thresholds for normal hearing levels. This is known as an audiogram and is used to graphically represent hearing loss on a defined scale.
Bone Conduction Audiometry
An audiometer can determine how well the cochlea (i.e., the spiral activity of the inner ear) functions. A device called a bone oscillator is placed on the forehead or behind the ear, usually as a headband and sounds are sent through the oscillator, causing the bones in the skull to vibrate. This bypasses the middle and outer ear to directly stimulate the cochlea. Both air and bone conduction testing are done to determine if someone has conductive hearing loss or sensorineural hearing loss.
Speech audiometry tests how well you can hear, understand, and repeat speech. You will wear a headset through which words are spoken at different volumes. This is measured as the speech reception threshold (SRT), which is the lowest level in dB that you can repeat half of the words correctly. In addition, you are assigned a word recognition score (WRS), the number of correctly repeated words out of the number of presented words.
How Can You Tell If You Have Hearing Loss From an Audiogram?
An audiogram is used to graphically represent hearing loss on a defined scale and it measures hearing ability and the degree of hearing loss. Simply put, it is a graph that shows the softest sounds you can hear at different frequencies and pitches. For reference, a face-to-face conversation is about 65 decibels (dB); sounds louder than 85 dB that you may hear at a live concert can cause hearing loss after only a few hours. The results of an audiometry test are an indication for the degrees of hearing loss:
- Normal hearing: -10 to 20 dB
- Mild hearing loss: 20 to 40 dB higher than normal
- Moderate hearing loss: 40 to 70 dB higher than normal
- Severe hearing loss: 70 to 90 dB higher than normal
- Profound loss: 90 dB or more
ASA/ANSI S3.6-2018 (R2023): Specification For Audiometers is available on the ANSI Webstore.