A tone audiogram, also known as a hearing curve, shows a person’s subjective hearing ability and is used by ear, nose and throat specialists as an examination option in audiometry. Values deviating from the norm obtained through the tone audiogram provide information about the possible causes of hearing disorders. Different sounds at different frequencies are perceived through headphones and must be identified as heard.
What is the tone audiogram?
A tone audiogram, also known as a hearing curve, shows a person’s subjective hearing and is used by ear, nose and throat specialists as an examination tool in audiometry. A tone audiogram includes an image-like representation of the sense of hearing and provides information about hearing ability. This is how hearing loss and the range of severity are determined. With the tone audiogram, the specialist explains the situation and takes action. The sound audiogram detects three different frequencies of the individual hearing threshold. This hearing threshold shows a sound so faint that it can barely be heard. A hearing threshold between 0 to 25 is normal. Sound strength or sound intensity is measured in decibels, abbreviated dB, and displayed on a vertical axis. If the axis is followed downward, the sound becomes louder. Zero decibels on the apex of the axis is the weakest tone that can be heard at all. Those who cannot hear this tone need not be generally incapable of perceiving tones. On the horizontal axis, the tone frequency, the pitch is measured in Hertz, abbreviated Hz. Logically, the tone frequency increases as you move to the right on the scale. A normal conversation reaches a frequency between 500 to 3,000 hertz. The right ear is marked with a red O, the left ear with a blue X. Deviating lines are easily identifiable by color and show the hearing threshold of each ear. If multiple markings show below 25 decibels, a hearing impairment may be present. However, background noise or the voices of multiple people are a challenge for human hearing, which filters all voices and sounds.
Function, effect and goals
A sound audiogram can provide valuable information about whether a hearing disorder is present. The result also provides further information in which frequency ranges sounds can no longer be fully perceived. In this way, the tone audiogram provides evidence of how far the loss of hearing has progressed and can serve as confirmation of the success of measures taken as part of a therapy. If the sound audiogram shows that sounds between 25 and 40 decibels cannot be heard, a mild hearing loss is present. For example, it is difficult for those affected to follow a conversation if it is loud in the background, external noise is added or several people are speaking at the same time. Between 40 and 70 decibels is a moderately severe hearing loss, which makes it difficult for patients to understand conversations in general. A specialist diagnoses severe hearing loss at decibels between 70 and 95, and patients are often advised to wear a hearing aid. For very severe hearing loss above 95 decibels, aids such as lip-reading, sign language or the assistance of a written interpreter are considered helpful. Performing a sound audiogram involves testing the transmission of sound to the inner ear. It involves measuring frequencies between ten kilohertz to 125 hertz at a variable volume between zero to 120 decibels. In high-tona audiometry, the range up to 20 kilohertz is measured. This test is performed in a soundproof chamber, a hearing test cabin, to ensure optimal results in the measurement and to avoid disturbing noises from the environment or from outside. These could inevitably falsify the test result. The air conduction curve is used to check conductive hearing loss, which usually originates in the middle ear. The hearing performance of the inner ear is tested by the bone conduction curve. The volume increases in increments of five decibels at a time. Usually, the patient indicates the perception of the sound by pressing a button or something similar. When measuring with the tone audiogram, conductive hearing loss can be diagnosed at the same time as hearing loss. This is a form of hearing loss, a so-called combined hearing loss. To achieve the best possible result with a tone audiogram, the cooperation of the person being examined is required.Only if the person actively cooperates and wants to do so, the information of the measured values is efficient and allows an optimal further treatment. The purpose of a sound audiogram is, of course, to determine or exclude an existing hearing disorder as well as to check the deterioration of an already known hearing disorder. In addition to the conductive hearing disorder, there is also a sensorineural hearing disorder, in which affected persons are particularly sensitive to loud noises and become excessively frightened. A trough-shaped depression in the bone conduction threshold curve at one to four kilohertz could indicate otosclerosis if there is an additional conductive disorder. If this dip is in the low and mid range, bass hearing loss, Meniére’s disease, which is associated with vertigo, may be the cause. A high frequency drop is typical for age-related hearing loss. That is why a timely clarification with the help of a tone audiogram is important. Noise-induced hearing loss is possible due to a C5 depression, a sensorineural hearing loss, and can also be clarified accordingly with the help of a tone audiogram.
Risks, side effects, and hazards
Since the tone audiogram is made with the support of the affected person, the result depends primarily on how the affected person reacts to the sounds played to him. If he misunderstands the instructions or is not really interested in treatment, this consequently also falsifies the results of the measurements. Also, taking medications, acute illnesses, and the like may, under certain circumstances, cause the perception of tones to change at the moment the tone audiogram is performed.
