Overview of Audiology Pure Tone Evaluation
Hearing loss is a very common long-term condition. It affects more than 25 million people in the United States who are aged 12 and older. Additionally, nearly one in five children may experience hearing loss, either temporarily or permanently, by the time they turn 18. Despite the significant number of people affected by hearing loss, many adults aren’t getting the right care or help for their hearing problems at the right time.
Treatment for hearing loss is highly dependent on the exact cause and extent of the hearing problem. A thorough hearing assessment is the first step. It gives the healthcare team the crucial information they need to decide on the best course of treatment. There are a few tests out there that help determine the type of hearing loss someone has. Two of these are the Weber and Rinne tuning fork tests. While they are helpful for a basic check and for identifying the kind of hearing loss, they can miss smaller details. For example, these tests might not pick up on mild hearing loss, or if someone is losing hearing in both ears, or a combination of conductive and sensorineural hearing loss.
For a more detailed examination, there’s a different kind of test known as a ‘pure-tone audiometry evaluation’. This test checks a patient’s hearing across the range of frequencies (or pitches) that we use in everyday listening. It can determine the level, pattern and type of hearing loss and give the healthcare team a lot more detailed information. This can help them figure out what is causing the hearing loss, whether it is likely to get worse or better, and what the best treatment strategy would be.
Anatomy and Physiology of Audiology Pure Tone Evaluation
Pure-tone testing is a type of hearing test that measures how well your ear and brain respond to different sounds or tones. This test uses two different methods to check your hearing.
In the air conduction test, sound travels into your ear, vibrates your eardrum, passes through a series of tiny bones in your ear, and then reaches a part of your ear called the cochlea. From there, the sound is transformed into a signal that your brain can understand.
In the bone conduction test, a device on the bone behind your ear sends sounds directly to your cochlea by making the bone vibrate.
By using both of these tests, doctors can figure out what kind of hearing loss you have. If the problem lies in the parts of the ear before the cochlea (like the eardrum or the tiny bones), it’s called conductive hearing loss. If the problem lies in the cochlea or afterwards (in the nerves leading up to the brain), it’s called sensorineural hearing loss. Some people may have both types, which is known as mixed hearing loss. In a few special cases, a condition might falsely appear as conductive hearing loss due to certain structural changes in the ear.
The term “third window” diseases refer to a situation where there’s an extra connection between the inner and middle parts of your ear. Just like windows, these connections let sound travel through them.
Why do People Need Audiology Pure Tone Evaluation
If you are worried about changes in your ability to hear, have had an injury to the ear, or suspect that you may have a disease of the ear, a pure-tone hearing test might be suggested by your doctor. This type of test can be helpful for a range of issues not limited to the perception of hearing loss, persistent ringing or buzzing sounds in your ears (known as tinnitus), increased sensitivity to normal levels of sound (known as hyperacusis), and tracking of potential hearing loss due to medications (ototoxic monitoring protocols).
It can also be useful for diagnosing issues such as balance problems or dizziness, problems with the middle ear, trauma to the brain or specific injuries to the temporal bone in the skull, exposure to loud noises or sudden loud sounds, failing a routine hearing screening, or delayed speech development in children. Furthermore, it can assist in identifying conditions that have a high risk for causing hearing loss.
When a Person Should Avoid Audiology Pure Tone Evaluation
It may not be possible to perform an accurate hearing test (pure-tone evaluation) if a patient is unable to respond reliably. This situation is often seen with children under 6 months old as well as patients who have developmental or neurological issues. Pure-tone tests may also not be suitable for people who simulate or fake symptoms for various reasons.
In cases where a patient can’t respond reliably, doctors use other methods to get a full understanding of their hearing health. These methods may include electric signal testing (electrophysiologic testing) or a test that measures the sounds produced in the inner ear (otoacoustic emission testing).
Equipment used for Audiology Pure Tone Evaluation
A pure-tone evaluation, more commonly known as a hearing test, usually takes place in a specially designed quiet room to limit interruptions from outside noises. The room and all the equipment used for the test follow guidelines set by the American National Standards Institute to ensure that every test is as consistent as possible.
An ‘audiometer’ is a device that generates the sounds used for testing. It can control various aspects of the sound such as its pitch, volume, and the way it’s delivered to your ears. Different equipment might be used based on what part of your hearing needs to be tested and any limitations of your ears. For example, the most commonly used types of equipment are different types of headphones and a device, known as ‘bone conduction oscillator’, that delivers sounds through vibrations.
If headphones cannot be worn, say in the case of kids, speakers set at specific angles to the testing seat are used. The sounds played through them are varied to avoid any interference caused by one consistent sound. This method is called ‘sound field testing’ and it measures the hearing ability of the better of your two ears. So, if the hearing characterised by the test comes out as ‘normal’, it doesn’t mean both your ears hear perfectly. It only means at least one ear could hear normally at each frequency tested. For this reason, this method isn’t useful for diagnosing one-sided hearing loss.
Regardless of how the sounds are delivered, normally, you would indicate that you’ve heard a sound by pressing a button, raising your hand, or verbally acknowledging it. Different methods can be used for kids who may have trouble giving reliable responses. These methods use games with visual or play stimuli to gather more reliable information.
Hearing screenings in school or hospital settings are done with portable hearing test devices, known as ‘portable audiometers’, which are calibrated (or set up) to accurately test the sound reception through air or bone conduction, or just through air, based on their models. They are designed to quickly assess your response to sounds at various frequencies to determine if further, more detailed, hearing tests are needed. If the conditions for testing are quiet enough, portable tests can be as accurate as those done in a sound booth.
Who is needed to perform Audiology Pure Tone Evaluation?
When there’s a need to check your hearing because of some concerns, a hearing test called pure-tone testing is usually done by a professional known as an audiologist. This person specializes in checking and improving people’s hearing. But when mass hearing tests are to be conducted, like for school kids or military officers, a simpler version of this test can be done. This simpler test is often handled using machines that run the test automatically, and it is done by a technical person trained in hearing tests, known as an audiology technician.
Preparing for Audiology Pure Tone Evaluation
During a pure-tone hearing test, patients sit inside a special booth designed to block out any other noises. The doctors will explain to them what’s happening during the test so they understand what to expect. If the patient is a young child, parents are educated on how the child will be tested, typically while sitting on their parent’s lap. Little ones may receive simple instructions to help them understand and feel comfortable with the test.
Before the test begins, a hearing specialist called an audiologist will put specific pieces of equipment (transducers) on the patient’s head or ears. Then, they will close the door of the sound booth and move to a neighboring booth where they can control the hearing test machine (audiometer). This separate booth allows the audiologist to watch the patient through a special window and listen to any feedback via a microphone set up in the patient’s booth.
How is Audiology Pure Tone Evaluation performed
Audiograms are graphs that we use to understand how well someone can hear. These charts plot the range of sounds someone can hear in terms of frequency (pitch) and loudness.
The horizontal line (X-axis) shows the pitch of sounds, from low to high frequency, measured in cycles per second, known as Hertz (Hz). The vertical line (Y-axis) shows the loudness of sounds, from soft to loud, measured in decibels of hearing level (dB HL).
In an audiogram, we adjust the scale slightly because normal human ears hear better in the middle-frequency ranges than at very high or low frequencies.
An audiogram tests hearing ability across a range of frequencies, from very low (125 Hz) to ultra-high (up to 20,000 Hz). One way we summarize the results is using something called the Pure-tone Average (PTA). It’s an average of how well someone hears at 500, 1000, and 2000 Hz. But, it’s important to remember that the PTA doesn’t give us information about how well someone hears at the very highest and lowest frequencies.
During the hearing test, different sounds of varying pitch and loudness are presented to the ear, and the individual’s responses are recorded. The level of hearing loss is categorized from normal to profound, based on how loud sounds need to be for the person to hear them. It’s noted that children should ideally hear sounds at 15 dB HL or less, for their developmental needs.
The type of hearing loss can be determined from an audiogram as well. If there’s not a big difference between hearing levels when tested through air (normal hearing process) and through bone (vibration), the hearing loss is classed as ‘sensorineural.’ If hearing levels differ significantly between the two tests, the hearing loss is termed ‘conductive.’ Mandatorily, a certain difference between bone conduction and air conduction is required to classify a hearing loss as ‘conductive.’ If there’s a mixture of these two kinds, it’s called ‘mixed’ hearing loss.
The shape of the plotted audiogram helps us understand the possible cause of hearing loss. For instance, a loss in high-frequency hearing could be due to aging (presbycusis), or a loss in middle-frequency could indicate genetic causes.
We may also use a technique called ‘masking’ during testing when we suspect that sound from the tested ear is getting picked up by the other ear. We introduce a noise into the non-tested ear to make sure that only the ear being tested is responding to the sounds. We complete both bone and air conduction tests for each ear, using masking techniques as needed.
Possible Complications of Audiology Pure Tone Evaluation
There are many things that can affect the accuracy of a hearing test, which professionals call a “pure-tone evaluation.” These factors could include things like the type of headphones used during the test, exactly where they’re placed, or even how alert and attentive the patient is. It’s normal for the results to be a little different each time a person takes the test. This variability tends to be within ±5 decibels for adults and ±10 decibels for children.
Sometimes, a tricky situation can occur during the test. This can happen when the noise meant to distract the opposite ear—used to stop sound from reaching that ear—ens up being loud enough to affect the ear being tested. This is called a masking dilemma and generally happens when a person has serious hearing loss in both ears.
Ear pain, which doctors call otalgia, specifically in the external part of the ear or the ear canal, might cause issues during the test. The sore ear could stop headphones from being properly placed for the test. Some people might have ear conditions which mean that regular headphones can’t be used. In these cases, the pressure from “on-the-ear” headphones could obstruct the ear canal and affect the test results. Insert earphones, which are placed into the ear canal, may prevent these issues from occurring and can also help reduce the chances of a masking dilemma happening. However, the bigger space created by a medical procedure like drainage tubes in the ear can cause the lower frequency sound thresholds to seem higher when insert earphones are used.
A person’s behavior can also complicate the hearing test. Someone might mistakenly indicate they’ve heard a sound because they’re confused by ringing in their ears (tinnitus), they pick up on a rhythm of sounds being presented, or they’re overly eager to do well on the test. This is especially common if passing the test might affect something like getting a job. On the other hand, if a person doesn’t consistently indicate they’ve heard a sound, it could be a sign that they’re not hearing the sounds, they don’t understand how the test works, or they’re not being truthful about their hearing.
A special test called the Stenger test can help figure out if a patient is pretending to have worse hearing in one ear than they actually do. The Stenger test presents a quiet tone to the better-hearing ear and a louder tone to the poorer-hearing ear at the same time. If the patient says they heard the sound, it’s likely that the hearing test results are correct. However, if they don’t indicate hearing the sound, they might be pretending not to hear the louder sound in the tested ear—this indicates that their hearing may not be as bad as they’re letting on. The Stenger test is good at figuring out if someone is faking hearing loss in one ear.
What Else Should I Know About Audiology Pure Tone Evaluation?
Pure-tone audiometry is a common and reliable way to check for hearing loss. This test works by playing a range of specific sound frequencies, or “pure tones”, through headphones. The person being tested simply indicates when they can hear the sound. A graph called an audiogram is then produced which shows the softest sounds a person can hear at different pitches or frequencies.
This method is widely used because it helps not only catch the presence of hearing loss, but also understand its type, extent, and pattern. The information gathered from the test can be used to diagnose the specific ear issue, provide peace of mind, monitor the problem, or decide if more investigations are needed. For instance, if your hearing suddenly worsens, a quick pure-tone test can check if you have a severe condition called sudden sensorineural hearing loss (SSNHL). It’s crucial to diagnose and treat SSNHL promptly, as the treatments work best when started early.
Different organizations have various guidelines describing what constitutes significant hearing loss. Overall, a certain amount of change or difference in hearing ability, either between your two ears or different sound frequencies, is typically considered notable. This can provide indications of specific ear concerns, such as noise-related hearing loss or ototoxicity — a side effect of certain drugs that can harm your inner ear or auditory nerve. A significant difference between the ears’ hearing ability could mean a specific kind of tumor called a vestibular schwannoma.
Apart from identifying hearing problems, pure-tone tests are used to measure a person’s sensitivity to loud sounds, a condition known as hyperacusis. They can also illuminate the cause of tinnitus, otherwise known as ringing in the ears. The test helps match the pitch and volume of this sound, which aids in finding the right treatment. However, please remember that pure-tone audiometry isn’t enough to diagnose all hearing issues, such as difficulty understanding speech in noisy environments. Additional tests, such as those for “central auditory processing disorder”, might be required for a complete picture of your hearing health.
