What is a Pure Tone Audiometry Test?
Pure tone audiometry is a fundamental hearing test to identify hearing loss type, degree, and pattern. It’s considered the gold standard because it’s widely available, reliable, and relatively easy for a trained healthcare practitioner to perform.
Pure-tone hearing tests are usually conducted in a quiet, specially designed booth to minimise outside noise.
The pure tone test uses simple sounds with only one frequency at a time, similar to striking a single key on a piano. The test plays sounds at different pitches (frequencies) and loudness levels (intensities) to determine the quietest sounds a person can hear. The main goal of this test is to measure the smallest volume of sound, or threshold, that an individual can detect at each frequency, helping to assess their hearing ability.
Different devices can be used to check how well sound travels through your ears. The type of device depends on the part of the ear being tested and any unique features of your ears. The standard tools used include over-the-ear headphones, earplugs inside the ear, larger headphones that fully cover the ears, and a small vibrating device placed behind the ear for bone conduction testing.
An audiometer, an electronic device, is used to conduct the test. It can produce pure tones (sounds at single frequencies) to assess the ears’ air and bone conduction pathways.
Air conduction testing involves transmitting tones through earphones to determine the softest sound level a person can hear, known as the hearing threshold. This process is conducted across frequencies for each ear, typically ranging from 250 to 8000 Hz.
A device placed behind the ear carries out bone conduction testing, directly testing the inner ear’s response to help distinguish between different types of hearing loss.
An audiogram, a chart visually representing a person’s hearing ability across different frequencies, plots the hearing thresholds, effectively mapping out their hearing profile.
Putre tone test results help diagnose hearing issues, provide reassurance, monitor ear health over time, and decide if further investigation is needed.
At Ear Health clinics in Auckland and Christchurch, a free hearing screening includes a pure tone test with air and bone conduction tests. However, if air conduction is normal, bone conduction is not done. A full diagnostic hearing test adds speech and tympanometry tests, and a report.
What is the Purpose of the Pure Tone Test?
The pure tone test is like a detective tool for our ears, helping to figure out the health of our auditory system, which includes everything from the outer ear to the brain’s hearing centres. This test uses two main pathways to uncover the story of our hearing: air conduction (AC) and bone conduction (BC).
Air Conduction Testing
Imagine sound waves travelling on a journey into your ear. In air conduction testing, these waves enter through the outer ear canal, vibrate the eardrum, and pass through tiny bones in the middle ear. Their final destination is the cochlea, a snail-shaped organ in the inner ear, where they get transformed into nerve signals. These signals then zip along the cochlear nerve (part of the eighth cranial nerve), whiz through the brainstem, and finally reach the auditory cortex, where we “hear” the sounds.
Bone Conduction Testing
In bone conduction testing, the skull bonve, typically the mastoid process behind the ear, vibrates to introduce sound waves directly to the cochlea. This method bypasses the outer and middle ear structures, directly stimulating the inner ear and auditory pathways.
Deciphering the Clues
By using both air and bone conduction testing, the pure tone test can tell us if hearing loss is:
Conductive: This means the problem is somewhere from the outer ear, through the eardrum, to the tiny bones in the middle ear.
Sensorineural: In this case, the issue lies in the inner ear (cochlea) or the nerve pathways leading from the cochlea to the brain.
Mixed: Sometimes, it’s a combination of both conductive and sensorineural issues.
There’s also something called the “third-window” phenomenon, which can make conductive hearing loss seem worse. It’s like having an extra path in the inner ear that shouldn’t be there (like semicircular canal dehiscence), changing how sound moves through the ear.
The pure tone test provides a clear map of hearing health, identifying where the problems are and what kind of hearing loss is present. It is a critical step in maintaining our auditory well-being.
Why Would You Need a Pure-Tone Evaluation?
A pure-tone evaluation is like a comprehensive check-up for your ears. It’s crucial for anyone who has worries about their hearing or has experienced any issues related to their ears. Let’s dive into why someone might need this test.
Hearing Concerns and Ear Troubles
Hearing Changes: If you’ve noticed a drop in your ability to hear or if sounds seem muffled or distant, a pure-tone evaluation can help pinpoint the problem.
Tinnitus: Do you experience ringing, buzzing, or whilst sounds sound in your ears? This test helps understand if it’s linked to hearing loss or other ear issues.
Hyperacusis: This test can assess your hearing sensitivity if everyday sounds suddenly seem too loud or unbearable.
Ear Drama: Are you experiencing ear pain, fluid discharge, or any trauma to the ear? Get it checked out.
Dizziness or Vertigo: Since balance and hearing are closely related, a pure-tone evaluation can help determine if your ears are causing you to feel unsteady or dizzy.
Monitoring and Investigation
Ototoxic Monitoring: Some medications can harm your hearing. Regular testing ensures your ears aren’t being affected.
Middle Ear Check-Up: Infections or fluid build-up can affect hearing and require monitoring.
After an Injury: Testing can assess any hearing damage if you’ve had a severe head injury or a fracture around your ear.
Exposure to Loud Sounds
Noise-Induced Hearing Loss: Have you been around loud machinery, music, or explosions? Even if you don’t think your hearing is affected, it’s good to get tested.
Blast Injury: This test is crucial for those exposed to explosive sounds to detect hearing damage early.
Speech Delays in Kids: A hearing test can rule out or confirm if hearing loss is a factor if a child isn’t talking as expected.
At-Risk Situations
Risk Factors: Some health conditions, family history, or genetic factors can increase the risk of hearing loss, making regular testing a wise choice.
In short, a pure-tone test is essential for anyone facing hearing-related issues, exposed to ear-damaging conditions, or simply wanting to ensure their auditory health is on track. It’s crucial to catch potential problems early and keep your hearing sharp.
When Is a Pure-Tone Test Unsuitable?
Sometimes, there are better options than a pure-tone evaluation. Think of the test as requiring active participation from the person being tested, like hitting the right notes in a musical performance. Getting the reliable responses we need for infants younger than six months or individuals with developmental delays or neurological impairments can be tricky.
And then some might not give us the straight story, like patients who are malingering (pretending to have a hearing problem) or have factitious disorders (where they create symptoms for various reasons). In these cases, relying on their responses might lead us down the wrong path.
That’s when we switch gears and look towards objective tests, such as electrophysiologic assessments or otoacoustic emission testing. These don’t rely on the patient’s active participation and can give us a clearer picture of their hearing health, ensuring we still get the full story of what’s happening with their ears.
How is Pure Tone Audiometry Performed?
Setting the Stage
Imagine stepping into a sound-proof booth, a quiet cocoon designed to shut out the world’s noise. The booth and its high-tech equipment are fine-tuned to specific standards, ensuring that the sounds you’ll hear are suitable for testing your hearing. The audiometer is at the heart of this process, a machine that can play sounds at different pitches and volumes precisely controlled for each ear.
The Team
Who performs these tests? An audiologist leads detailed diagnostic testing. However, other healthcare professionals using automated devices can conduct the initial assessments. For example, ear nurses can perform hearing screenings at Ear Health clinics in Auckland and Christchurch.
Prepping for the Journey
Before the test, clients are guided on what to expect, focusing on making them comfortable and informed. The audiologist prepares everything before leaving the booth. From there, they control the test and observe through a window, ready to attend to every nuance of the client’s testing experience.
The Tools of the Trade
In this quiet sanctuary, various “headphones”, known as transducers, come into play, each chosen based on what part of your hearing journey needs exploration. The lineup includes:
Supra-aural headphones: Sit snugly on the ears, funnelling sounds directly into the auditory canal.
Insert earphones: These are tiny and discrete, fitting right into the ear canal for a direct and isolated listening experience.
Circumaural headphones: Envelop the ears entirely, creating a seal to keep any external noise at bay.
Bone conduction oscillators: Bypass the outer and middle ear, sending vibrations straight to the cochlea.
Interactive and Adaptive Testing
Responding to the sounds in the test can vary from simple actions like pressing a button, raising a hand, or verbally acknowledging the sound. The test can include visual reinforcement and conditioned play audiometry techniques to make the process more engaging and ensure accurate responses. These approaches add a game-like element to the procedure, utilising interactive tasks and stimuli to provoke responses. This method not only makes the testing experience more enjoyable but also enhances the effectiveness of the evaluation for participants of all ages.
Screening Outside of the Clinic
Portable audiometers are helpful outside the clinic, such as in schools or remote communities. Though compact, they are powerful enough to conduct screenings, checking for basic hearing capabilities at key frequencies to decide if a more in-depth examination is needed.
Pure Tone Test Results
The Audiogram Unveiled
Think of an audiogram as a map that traces your hearing capabilities. This graph charts sound frequencies, measured in Hertz (Hz), against their loudness in decibels of hearing level (dB HL), creating a landscape of your auditory range. Due to the unique way we hear, this map is adjusted to highlight how humans perceive mid-range frequencies better than very high or low ones. It’s like changing the brightness on your screen to see a picture more clearly.
The Testing Symphony
Starting at the comfortable pitch of 1000 Hz, the test plays a melody of pure tones across a spectrum, fine-tuning the volume to find the softest whisper you can hear. This journey through sound helps paint a precise picture of your hearing profile.
Categories of Hearing Loss
Hearing loss levels are quantified in decibels (dB), with your audiologist categorising them from mild to profound based on severity. Here’s how these categories break down:
- Mild (26 – 40 dB): Soft sounds, like a whisper or a child speaking, may be missed or hard to understand.
- Moderate (41 – 55 dB): Normal conversations, especially against background noise like in a crowded place or a busy café, become difficult and exhausting.
- Moderately severe (56 – 70 dB): Following conversations becomes challenging in most situations, especially without visual cues like lip-reading.
- Severe (71 – 90 dB): Normal speech becomes impossible to hear, turning conversations into silence.
- Profound (91+ dB): Almost all sounds are undetectable, leaving speech and most environmental noises unheard.
The Nature of Hearing Loss
Once established, the air (AC) and bone conduction (BC) thresholds help to reveal the type of hearing loss:
Sensorineural: Similar AC and BC levels point to issues beyond the middle ear, such as those in the inner ear or auditory nerve.
Conductive: Normal BC, but varying AC levels indicate a blockage or problem in the outer or middle ear.
Mixed: A combination of both, showing sensorineural and conductive loss traits.
Reading the Hearing Landscape
The audiogram’s shape offers clues to the underlying cause of hearing loss, whether it’s a gradual high-frequency decline indicating age-related changes or a specific dip pointing to genetic factors.
Navigating Sound Crossroads
When sounds are loud enough, they can reach the opposite ear, potentially muddling the results. This cross-ear journey, known as interaural attenuation (IA), varies by person and headphone type. The tester uses masking noise in the non-testing ear to ensure that only the ear undergoing the test hears the sound, helping to isolate the location of the hearing loss.
The Complete Hearing Assessment
A thorough, pure-tone evaluation involves testing both ears using air and bone conduction methods, with masking applied as needed to isolate each ear’s hearing capacity accurately. This comprehensive approach ensures a complete understanding of your hearing health, paving the way for further testing and tailored hearing solutions.
The Shape of Your Hearing
The audiogram’s shape offers clues to the cause of hearing loss. For instance, a high-frequency decline might point to age-related changes, while a mid-frequency dip could suggest genetic factors.
What Are Some Challenges of Pure Tone Audiometry?
The Tricky Terrain of Testing
Several factors make the journey to accurate results bumpy in pure-tone audiometry. The type and placement of transducers (like headphones or earphones) can slightly change the test’s outcomes, as can the patient’s level of alertness and attention. Ear pain or abnormal ear structure can make it challenging to place headphones correctly, affecting the test’s accuracy.
The Masking Dilemma
Imagine attempting to block out noise from one ear without affecting the other; this is known as the masking dilemma. It occurs when the noise used to block sound in the non-testing ear (NTE) is so loud that it travels back to the ear being tested, potentially misrepresenting the hearing threshold. This situation is prevalent in cases of severe hearing loss affecting both ears.
Behavioral Bends in the Road
Clients may produce false positive responses, indicating they hear a tone when they don’t. This may be due to conditions such as tinnitus, a rhythmic tone pattern, or eagerness to pass the test, especially when associated with job qualifications.
On the other hand, false negatives, where patients don’t respond to sounds they can hear, might be caused by misunderstandings of the test process, processing difficulties, or intentional attempts to manipulate the results.
The Stenger Test: Unmasking the Truth
When suspecting feigned hearing loss, audiologists use the Stenger test, which plays tones to both ears, intentionally making one sound softer in the ear under suspicion. If the patient claims not to hear the louder tone in the better ear, focusing instead on the softer tone in the other ear, this behaviour may indicate an exaggeration of their hearing loss.
The Stenger test is a clever method for verifying the authenticity of hearing loss claims, particularly when the loss is reported to be more severe in one ear.
Pure-Tone is Not A Panacea
Remember that pure-tone audiometry isn’t a one-stop shop for diagnosing all ear and hearing issues. Specifically, it doesn’t fully capture the nuances of auditory neuropathy or central auditory processing disorders, where challenges like understanding speech amidst background noise come into play.
Speech audiometry or other specialised tests are necessary to view these conditions comprehensively. Patients typically need to be school-aged or older to evaluate central auditory processing disorders and capable of focusing on the lengthier, more involved assessment process.
