Audiology clinicians diagnose and treat a patient’s hearing and balance problems using advanced audiology technologies and procedures. Audiologists must earn a doctoral degree to practice, and help patients. All audiologists must be licensed; filling different requirements that vary from state to state.

Audiology 101: Audiogram

Audiogram In the field of audiology, an audiogram is a graph that shows the softest sounds a person can hear at different frequencies. You can think of this graph as a piano keyboard, with low frequencies (notes) on the left and high frequencies (notes) on the right. The audiogram displays soft sounds near the top of the graph and loud sounds near the bottom. Recording responses on the audiogram is done using an IX/ to represent the left ear and an /0/ to represent the right ear. Color designations are often used to distinguish the left from the right ear. Left scores are typically recorded in blue ink, while right ear scores are typically recorded in red ink. The frequencies are measured in Hertz (Hz).

The goal of an audiogram is to obtain thresholds for each ear that are frequency and intensity specific. Thresholds are defined as the softest sounds that a patient believes he/she can hear. Therefore, when obtaining audiology thresholds, the patient should respond consistently to each presentation tone about three times at the softest level possible. Hearing is NOT measured in percentages. Rather, it is measured in an arbitrary unit of loudness called the Decibel (dB). The audiogram has been translated from a measure of simply “how much physical pressure is needed for sound to occur” – Sound Pressure Level (SPL) to “what should a normal hearing person hear?” – Hearing Level (HL). This means, that zero dB on the graph, does not signify the absence of sound, but rather a very soft sound that someone with perfect hearing should hear. This helps the clinician compare the patient’s hearing to normal hearing and answers the “real” question that brought the patient to the clinic: “Do I have a hearing problem?”

Normal hearing is defined as thresholds equal to or better than 20dB at each of the speech frequencies. The frequencies tested typically included 250 Hz through 8000 Hz. A person with normal inner ear or cochlea function can hear sound from approximately
20 Hz to 20,000 Hz. As we age, this range of frequencies diminishes.

The frequencies on the audiogram represent the frequencies we use for speech understanding. Even though we may be able to hear a sound at 14,000 Hz, this frequency does not contribute to our speech understanding ability.

Unfortunately, even with slight hearing loss in the high frequencies, patients will typically have difficulty discriminating high pitch speech sounds. Occasionally, a patient with this type of high frequency loss will state that people are ‘mumbling’ or ‘need to enunciate more clearly.’ This is because he/she may have a loss of speech understanding resulting from the high frequency hearing loss.

Audiology 101: Audiometric Evaluation

The full audiometric evaluation will typically begin with an in-take or case history questionnaire. Prior to running any audiometric tests an Otoscopic evaluation (visual inspection of the outer ear) is performed
to rule out excessive ear wax, fluid or other blockage of the ear canal, which could contribute to a hearing loss. Pure tones thresholds including both air and bone conduction, speech assessments including, but not limited to, SRT and WRS measures and middle ear assessments including Tympanometry and Acoustic Reflexes are all part of a standard comprehensive evaluation.

Pure-tone testing

The measurement of hearing sensitivity to pure-tone stimuli at discrete frequencies in sound field through speakers or through headphones. Loudness Discomfort Level (LDL): LDLs are measured in dB to indicate a patient’s loudest possible tolerance for a specific sound. This test can be frequency specific or measured using speech in the sound booth. It can be helpful in determining reduced dynamic range (distance
between threshold of audibility and level of discomfort for any particular sound), which is often present in patients suffering from sensorineural hearing loss or tinnitus.

Speech Testing

The measurement of hearing sensitivity to speech sounds through sound field speakers or through headphones. There are several ways in which speech understanding is evaluated.

Speech Awareness Threshold (SAT)

The lowest level at which the patient can hear and repeat words.

Word Recognition Score (WRS)

The percentage of words correctly repeated from a list of words. This test reflects the ability of a patient to hear AND understand speech in a quiet environment. The speech discrimination test can also be conducted in noise. Typical speech-innoise tests will have somewhere between a +15 to +5 signal-to-noise ratio (SNR) to simulate a typical noisy environment.

Standard Audiometry

The standard testing technique for measuring hearing acuity is to have the patient raise a hand, press a button or otherwise signal to the tester that he/she heard the sound stimuli presented. Standard audiometry can be conducted with headphones, speakers or insert earphones. In each case sounds are presented in pure-tones across the speech frequencies and will travel through the outer, middle and inner parts of the ear in order to be heard. The patient is asked to signal to the tester each time he/she perceives a pure-tone. This is referred to as “air-conduction” thresholds. This is when the IX/ or /0/ symbols are used to identify thresholds
of hearing for each ear on the audiogram or hearing graph. Following this same process, a bone oscillator is used next to obtain frequency specific thresholds, skipping the outer and middle ear and traveling directly to the “better” hearing ear’s cochlea (inner ear). In most circumstances it will be tested monaurally (only in one ear) if both ears’ air-conduction thresholds are symmetrical (similar or the same). A difference between air and bone conduction threshold measures is referred to as an air/bone gap. In this case the bone-conduction thresholds should be measured individually using “effective masking” in the non-test ear to ensure the responses obtained from the bone oscillator are valid for the test ear. The presence of an air/bone gap necessitates a medical referral since this indicates a potential middle ear abnormality.

Audiology 101: lmmittance Testing

lmmittance testing assesses middle-ear function using changes in air pressure and loud sounds. There are several types of lmmittance testing as outlined in this section.

Tympanometry

Measures the movement of the tympanic membrane (eardrum). If the eardrum does not move well, sound will not travel efficiently to the inner ear and the patient will typically have a mild to moderate hearing loss.

Acoustic Reflexes

Measures the contraction of the middle-ear muscles in response to a loud sound. Patients with moderate or worse hearing loss often do not have a measurable acoustic reflex response.

Eustachian Tube Function

Evaluation of the Eustachian tube’s ability to maintain equal pressure within the middle ear space or pressurize the outer and middle ear spaces.

Auditory Brainstem Response (ABR)

An ABR is a test used to predict hearing sensitivity and to assess the integrity of the auditory nerve and auditory brainstem structures. This test allows the clinician to measure how the auditory nerve responds to sound without the active participation of the patient. Several surface electrodes are placed in calibrated positions on the patient’s head in order to record brain wave activity. This type of testing can give a good indication of hearing sensitivity without requiring any response from the patient. It is reliable and often used with patients who cannot {or will not) give a standard response. The noise level of the environment
and/or the noise level of the patient will affect the reliability and validity of the test. If the patient is asleep, the testing may be more accurate. This test suggests normal cochlear function, but not
necessarily normal hearing or processing of sound.

Evoked Otoacoustic Emissions (EOAEs)

This is a test used to evaluate the integrity of the inner ear or cochlea. It is an actual measurement of an echo that is elicited in the hair cells of the cochlea as sounds travel through the inner ear. If the patient’s inner ear structures are intact and functioning, a normal OAE will be recorded. Patients without recordable OAEs, often have a mild hearing loss or worse. This test does not require the patient to respond or actively participate and thus it is frequently used to screen babies for hearing loss. These audiology measurements are less affected by environmental noises and patient noises. However, the testing will take longer if the patient or the environment is noisy. In some cases, noise can affect the accuracy of the test.