Severity
When performing Pure-Tone Audiometry, the severity of the hearing loss is often the first information obtained by the audiologist. As mentioned above, pure tones are presented through air conduction at different frequencies when using headphones or insert earphones. Audiologists often start at a softer volume and work their way up in amplitude until a patient responds. These responses are then plotted on a graph in decibels by frequency. The decibel level that a patient responded to >50% of the time at each frequency represents the severity of loss. For example, if an individual responds to sound presented at 55 dB HL for 500 Hz tones, that would mean they have a moderate hearing loss at that frequency.

Nature
Air conduction testing, however, does not provide complete information on the nature or etiology of hearing loss. To obtain these results, audiologists must take advantage of another method of hearing – bone conduction. When testing bone conduction, a bone oscillator is placed on the mastoid process. The bone oscillator then vibrates to send stimuli, pure tones, to the inner ear. When stimulating the inner ear directly, the outer and middle ear are bypassed. This allows audiologists to discern if hearing in the inner ear differs from hearing through the outer and middle ears. If there is a discrepancy between bone and air conduction thresholds, a provider can determine that there is some pathology involving the outer and/or middle ear contributing to the hearing loss.

There are 3 classifications of hearing loss; conductive, sensorineural, and mixed. When bone conduction thresholds are normal and there is a discrepancy between air and bone conduction thresholds by more than 10 dB, this is classified as a conductive hearing loss. With this type of loss, the inner ear is healthy and hearing normally, but there is some pathology in the outer and/or middle ear affecting the transmission of sound. When there is diminished hearing through both bone and air conduction, and there is no difference between the thresholds, this is classified as a sensorineural hearing loss. With this type of loss, there is diminished hearing ability in the inner ear alone. With a mixed hearing loss, all parts of the ear contribute to the overall loss. Results of a mixed loss would present as diminished bone conduction thresholds, representing a loss in the inner ear, as well as diminished air conduction thresholds. There would also be a difference in air and bone scores. In other words, an individual with a mixed hearing loss has an underlying inner ear issue causing diminished hearing acuity as well as an outer and/or middle ear pathology causing a further decline in hearing thresholds.

Ear Specific Information
At times, hearing loss will differ between ears. Headphones and insert earphones are used to provide audiologists with ear specific results. When testing bone conduction, however, no matter which mastoid the oscillator is placed, the entire skull is vibrating. When there is a difference between each ear’s hearing acuity, this phenomenon makes it difficult to tell which ear is responding. Amplitude can also make it difficult to separate each ears results even when testing through headphones or insert earphones. If a sound is loud enough, it can stimulate the non-test ear despite it being presented to the other side. In these two scenarios, masking is used to isolate each ear and obtain results for each. In short, masking is a method of ensuring the ear you are not presently testing, the non-test ear, is not responding to the presented stimuli. You can then determine the severity of loss in each ear individually.

Most Comfortable Loudness Levels (MCL) and Uncomfortable Loudness Levels (UCL)
Beyond hearing acuity, pure tones can be used to determine at what decibel level a patient is most comfortable listening to and understanding sound. Audiologists can present tones at different levels and frequencies and use patient report to determine at what level each pitch is most comfortable. Similarly, uncomfortable loudness levels can be determined by presenting pure tones at each pitch at increasing amplitude levels.

The audiogram is the graph in which the clinical plots hearing levels. Hearing levels describe the deviation from what is considered normal hearing. The audiogram contains frequency information on the x-axis, listed from low to high pitch, and amplitude or volume on the y-axis, measured in decibels (dB HL). Responses to pure tones, usually ranging from 250 – 8000 Hz, are indicated on this graph. Data is recorded using a variety of standardized symbols that are delineated by ear, transducer, and masking status. Once testing is complete, the audiogram contains data regarding the severity, classification, and configuration, or shape, of the hearing loss.

The test typically takes about 20-30 minutes to complete but may vary depending on the individual's responsiveness.

The most important piece of equipment needed to perform pure tone audiometry is your audiometer. This device will allow you to present tones at the desired volume and frequency. Clinicians will also need transducers, primarily headphones, but possibly also a bone oscillator. In addition, some professionals prefer insert earphones. Ideally, pure-tone audiometry should be performed in a soundproof booth to ensure accurate results.

Most audiometers, like Measure's diagnostic audiometer and fitting unit, also allow for free-field testing using a speaker as transducer. This test is ideally done in a soundproof booth. It should be noted that when testing with free-field sound, no conclusions can be drawn regarding which ear that is responding, as ear-specific information cannot be obained through these means.

Clinicians can utilize the Measure software and audiometers to accurately perform pure tone audiometry testing. As the results of this type of testing guide a clinician’s treatment and management of an individual’s hearing loss, having high-quality and reliable equipment is paramount.