What Is Pure Tone Audiometry? Learn Why This Hearing Test is So Important

nurse conducting a hearing test to a patient

Hearing loss cases are on the rise globally. The World Health Organization (WHO) predicts that more than 5 percent of the world’s population will require hearing rehabilitation and by 2050, nearly 2.5 billion people will have some degree of hearing loss.

Early detection is the key to prevention.

Pure tone audiometry testing is one of the many tools hearing professionals use to assess hearing loss. This article will tell you everything you need to know about pure tone testing and the role this vital hearing test plays in clinical audiology.

What Is Pure Tone Audiometry Testing?

Pure tone audiometry is a hearing test that uses pure tones to measure an individual’s hearing sensitivity. Pure tones are simple sine waves played at a given frequency, with no complex characteristics that one hears in naturally occurring sounds.

Pure tone testing attempts to establish a “hearing threshold.” This refers to the softest sound a person can hear. Audiologists will apply the test using different pathways—air and bone conduction—to determine the type of hearing loss.  

Why Is Pure Tone Audiometry Performed?

When a person shows signs of hearing impairment, a doctor will usually order a hearing test to determine the extent of the hearing loss and figure out the cause.

Pure tone audiometry testing aims to precisely quantify your ears’ ability to hear.

An audiologist will perform the test and study the resulting graph or audiogram to see if your hearing falls within the normal limits.

While a battery of tests is required for a comprehensive hearing evaluation, pure tone audiometry is the starting point. It identifies the type of hearing loss and gauges the severity.

The audiometry results are relatively accurate and more reliable than other hearing tests. This is why pure tone audiometry is considered the gold standard of hearing tests.

Pure tone audiometry is considered the gold standard of hearing tests because the audiometry results are more reliable than other hearing tests.

Types of Pure-Tone Tests

As we’ve already mentioned, pure tone audiometry involves both air conduction and bone conduction testing. The former follows the normal sound pathway from the outer to the middle ear, while the latter sends tones directly to the middle ear.  

The difference between air and bone conduction thresholds helps determine the type of hearing loss by pinpointing the exact location where the breakdown in the hearing mechanism occurs.  

Air Conduction

In an air conduction test, the audiologist transmits sounds into the outer ear through the ear canal into the eardrum.

Air conduction testing is performed using over-ear headphones or insert earphones, and it measures well you can perceive sounds transmitted through the air.

Bone Conduction

Bone conduction tests measure how well you can perceive sounds transmitted through the bone. It is a direct test of middle ear function. In bone conduction tests, the audiologist stimulates fluids in the middle ear with vibrations in the skull, which the auditory nerve detects.

Bone conduction testing involves placing a vibrating instrument called a bone oscillator where the jaw connects to the test ear.

How Is Pure Tone Audiometry Done?

Pure tone audiometry is a subjective hearing test, meaning it relies on self-reporting rather than a direct measurement. It’s a risk-free non-invasive test where the audiologist plays tones and then asks the patient if they can hear them.

Before the test begins, the professional may ask questions about your family history, medical history and hearing health status.

Equipment

Pure tone audiometry is performed using measurement and sound-generating equipment that meet the applicable American National Standards Institute (ANSI) specifications.

The two main types of equipment are:

AudiometerAn audiometer is an electric instrument with a pure tone generator, an attenuator for varying intensity, and a microphone. Several types of audiometers are available, ranging from handheld screening audiometers to full-fledged diagnostic audiometers.
TransducerA transducer is used to send pure tones to the test ear. For air conduction testing, audiologists use over-ear headphones and insert earphones. Bone conduction tests use a bone oscillator placed behind the jaw just below the test ear.

Environment

A quiet, distraction-free testing environment is necessary for accurate and reliable results. Any outside noise can affect the patient’s ability to hear the test tones, so pure tone audiometry is performed in soundproof rooms.

All audiometric must have walls coated with sound-absorbing materials and meet the ambient noise levels specified by ANSI.

Procedure

The audiologist will play pure tones of varying loudness at frequencies ranging from 250 Hz to 8 kHz to determine the softest sound level the patient can hear at least 50 percent of the time.

Before the test begins, the tester will instruct the patient to raise their hand or press the response button every time they hear a tone.

The audiologist will perform the test using headphones and a bone oscillator to test air and bone conduction, respectively. Afterward, they’ll compare the air and bone conduction thresholds to determine the type of hearing loss.

Speech audiometry is usually done along with pure tone testing. It uses sounds of people talking instead of pure tones to assess hearing thresholds for being able to detect and comprehend speech. The speech recognition threshold is the lowest level at which a person can repeat back at least half of what is said.

Testing Young Children

Young children may find it difficult to follow the instructions, so audiologists have developed variations of pure tone audiometry that involve games and conditioning to elicit a response from younger patients.

Using Pure Tone Audiometry To Diagnose Hearing Loss

During pure tone audiometry testing, the audiologist records the patient’s responses to tones played in the test ear using different symbols in a graph called an audiogram.

Audiogram Shape

The shape of the audiogram provides information on the type and possible causes of hearing loss. For instance, a flat increase in thresholds from low to high frequencies is a sign of conductive hearing loss or middle ear disorders, whereas a notch at 4,000 Hz indicates noise-induced hearing loss.

Pure Tone Average

The tester also calculates the pure tone average to determine the severity of hearing loss. This is quantified in a unit called hearing loss in decibels, or “dB HL” for short.

Normal hearing is defined as -10 to 15 dB HL. Someone who scores higher than 90 dB HL is considered profoundly impaired.

The table below shows standard classifications of hearing loss.

Hearing loss range (dB HL)

Degree of hearing loss

-10 to 15

Normal Hearing

16 to 25

Slight

26 to 40

Mild

41 to 55

Moderate

56 to 70

Moderately severe

71 to 90

Severe

91+

Profound

Source: American Speech-Language-Hearing Association

Bilateral and Unilateral

The audiologist tests the right and left ear separately to get ear-specific information and determine if the hearing loss is occurring in one or both ears. If you have normal hearing in one ear and impairment in the other, that’s considered unilateral hearing loss.

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This provides a vital clue about the underlying condition. For example, when hearing loss is caused by a medication that is toxic to the ear, it will be bilateral, affecting both the right and left ear.

However, eardrum ruptures and blockages most often occur in only one ear at a time, resulting in asymmetrical hearing loss.  

Types of Hearing Loss

Hearing impairment is classified based on the point in your auditory system where the disorder occurs. Hearing loss is broken down into three categories.

Conductive hearing loss

This form of hearing loss occurs due to an obstruction or defect in the outer or middle ear that interferes with the sound waves on their way to the inner ear. This type of hearing loss is often reversible through treatment or surgery.

Common causes of conductive hearing loss include:

  • Ear infections
  • Earwax buildup
  • Punctured eardrum

A person diagnosed with conductive hearing loss will be referred to an ear, nose and throat specialist for wax removal, medications or other medical treatments.

Sensorineural hearing loss

This type of hearing loss is caused by damage or degradation to the hair cells of the inner ear or the auditory nerve. Common causes of sensorineural hearing loss are:

  • Constant exposure to loud noise
  • Aging
  • Neurological conditions

Sensorineural hearing loss is usually irreversible. It cannot be fixed through medication or surgery.

The most common treatment options are hearing aids and cochlear implants.

Mixed hearing loss

Mixed hearing loss is a combination of conductive and sensorineural hearing loss. This means you simultaneously have a problem in your inner, outer and middle ear.

An example is a person who suffered severe trauma from an explosion that physically damaged the outer ear and delicate mechanisms inside. It could also be a person with age-related hearing loss who develops an earwax blockage due to hearing aids.

The treatment options for mixed hearing loss depend on the location and extent of the damage.

After Audiometry Testing

After estimating the type and degree of your hearing loss, the audiologist will recommend different treatment options such as hearing aids, cochlear implants, and other medical treatments.

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If you are exposed to high levels of noise daily, the professional will suggest various preventive measures, such as hearing protection and changing occupations. If they believe your hearing loss is due to underlying medical conditions, the audiologist will refer you to appropriate medical specialists.

Accuracy of Pure Tone Audiometry

Pure tone audiometry is a reliable diagnostic test that can measure an individual’s hearing sensitivity.

According to AAFP, handheld audiometers have a 94 percent success rate for detecting sensorineural hearing loss or inner ear disorders.

Moreover, the audiometry testing procedure typically involves retesting the person’s threshold for accurate results. The tester will make sure the patient hears the tone in at least two out of three trials before recording the response.

However, audiometry testing can be challenging in younger children who cannot follow the test instructions. Therefore, objective hearing tests are typically recommended for younger patients.

Another limitation of audiometry is that it cannot identify all types of hearing loss, such as Auditory Processing Disorders (APD), a neurodevelopmental disorder that affects how the brain processes auditory information.

In short, pure tone testing alone cannot provide a total picture of all the ear’s components or every underlying neurological mechanism that may contribute to hearing impairment.

A battery of hearing tests is necessary to fully evaluate a person’s hearing ability.

Cost of a Pure Tone Audiometry Test

A pure tone audiometry test typically costs around $250 without insurance. However, the price may widely vary with clinic location, practitioner, and insurance policy.

Before you book an appointment, ask your insurance provider if hearing services are covered under your plan. If your health plan covers hearing tests, make sure you visit a hearing clinic in your network. If not, you may not be eligible for reimbursement.

If the professional recommends hearing aids, try them first to see which one suits you the best.

The cost of hearing aids ranges from $1,000 to $6,000.

When to Get a Pure Tone Hearing Test

American Speech-Language Association (ASHA) recommends getting a hearing test at least once every 10 years before the age of 50 and every three years after that.

Consult a licensed audiologist for a comprehensive hearing examination if you suspect hearing loss.

If you’re over the age of 50, you should get your hearing tested every 3 years, according to the American Speech-Language Association.

Common signs of hearing impairment:

  • You often ask others to repeat what they said.
  • You cannot understand speech in noisy environments, such as parties and crowds.
  • People often ask you if you have trouble hearing.
  • You have difficulty talking on the phone.
  • You watch TV at a louder volume than your family members.

You can also take online hearing tests, such as ones offered by ReSound, Phonak, and Starkey. While useful for determining if you need help, online tests should not be considered a substitute for professional testing. Contact a licensed hearing professional if you experience hearing loss.

Conclusion

Pure tone audiometry is one of the most effective ways to detect age-related and noise-induced hearing loss. In this standard hearing test, an audiologist sends pure tones to the test ear via air and bone conduction to determine if your pure tone thresholds are in the normal hearing range.

This safe, non-invasive test is usually the first step to diagnosing and effectively treating hearing loss. If you’re having hearing problems or if it’s been a while since your last hearing exam, set up an appointment with a specialist today.