Masking Definition Audiology

16/11/2022por Mentores

A common problem with masking in audiometric testing is the location of the masking tray. This is called a masking dilemma and occurs when there is moderate to severe bilateral conductive hearing loss. In this case, the intensity of the masking noise in the untested ear switches to the test ear and increases the thresholds. This means that the clinician would continue to wear a mask without reaching the plateau. Sounds interact in different ways, depending on the difference in frequency between the two sounds. The two most important are cubic difference tones [definition needed] and square difference tones [definition needed]. [5] If a threshold is stored during masking, the final masking level is stored in the masking table under the ear being tested. The term “effective masking” in this situation refers to the fact that the narrowband noise level was loud enough to effectively mask pure sound of the indicated level heard by the masked ear. Here, the difference between air conduction and bone conduction is greater than 55 dB (interaural attenuation), which is why masking is necessary. Yellow indicates that masking is recommended stronger and that a wide range must be enabled in order to adjust channel 2 to the correct level. This is especially useful in teleaudiology cases, as it`s important to make sure you can trust your results when performing remote tests.

Interacoustic`s masking assist is available to help you decide on a safe and correct masking intensity. When masking assist is enabled, a status light on channel 2 indicates whether masking was applied correctly. First, we need to understand the science and reasoning behind OSH masking. We also need to cover some of the related concepts, such as interaural attenuation (AI) and occlusion effect (OE). You may already be familiar with these terms, but we`ll shed some light on how they all work together. If unmasked hearing thresholds are established and it has been determined that mask wearing should be applied, the effective masking threshold for the untested ear must be reached. [6] This is the strength of the masking sound to prevent hearing crossed by the ear untested. Several methods are used to determine the effective masking level for each frequency to be tested, often with an initial masking tone similar to the threshold of the unmasked airline used. This is played in the non-test ear via over-ear headphones or inserted headphones, while the exact new threshold of the test ear is determined using the same procedure described above for a pure sound audiogram. The masking noise in the untested ear is increased at regular intervals, with the pure sound thresholds in the test ear being tested at each new interval until a “plateau” threshold is found.

This is the level at which the masking sound is loud enough to avoid hearing pure sound through the untested ear, but not loud enough to hear the masking sound in the test ear, known as “overmasking.” [7] [8] There are different rules for masking around the world, but some general masking rules are as follows: In the example above, channel 2 must be set to right (non-test ear) using the preferred masking stimulus (usually NB). Make sure Rev is active to make sure the masking sound is continuous. Channel 1 should be set to links (test ear) with the preferred stimulus (usually sound). The masking frequency changes automatically with the sound frequency when masking is enabled. You can set masking and tone frequencies using the frequency reduction buttons. When trying to determine the true threshold of the left ear, the right ear is now distracted by noise. Masking is not possible if the required level of masking simultaneously results in overmasking: the masking pattern changes depending on the frequency of the masking and the intensity (Figure B). At low levels in the 1000 Hz diagram, such as in the 20 to 40 dB range, the curve is relatively parallel. As the intensity of the masquerade increases, the curves separate, especially for signals with a higher frequency than the masker. This shows that there is a dispersion of the masking effect upwards when the intensity of the masking is increased. The curve is much flatter in high frequencies than in low frequencies.

This flattening is called upward propagation of masking and is the reason why interfering sound masks high-frequency signals much better than low-frequency signals. [1] This audiogram shows hearing loss on the right side, but masking is necessary to determine true thresholds. Harvey Fletcher conducted an experiment to find out how much a sound group contributes to the masking of a sound. In the experiment, a fixed sound signal centered different bandwidths of noise. The hidden threshold was recorded for each bandwidth. His research has shown that there is a critical range of noise that causes the maximum masking effect, and that energy outside this band does not affect masking. This can be explained by the fact that the auditory system has a hearing filter focused on the frequency of the sound. The bandwidth of the masker inside this hearing filter effectively masks the sound, but the masker outside the filter has no effect (Figure G). The amount in which the masking increases the signal threshold is much lower with off-frequency masking, but has some masking effect because part of the mask overlaps the auditory filter of the signal (Figure E)[5] Auditory masking is used in tinnitus maskers to cause annoying ringing, whistling or buzzing, or tinnitus, often associated with hearing loss, to be removed.

It is also used in various types of audiometry, including pure sound audiometry and standard hearing testing to test each ear unilaterally and test speech recognition in case of partially masking noise. The Kuduwave masking strategy saves the doctor valuable time in determining masked thresholds more accurately. It can be masked manually or automatically for bone conduction, automatically taking into account the occlusion effect. The effectiveness with which the mask increases the signal threshold depends on the signal frequency and the frequency of the masker. The diagrams in Figure B are a series of masking patterns, also known as masking audiograms. Each graph shows the amount of masking produced at each masking frequency displayed in the top corner, 250, 500, 1000 and 2000 Hz. For example, in the first graph, the mask with a frequency of 250 Hz is displayed simultaneously with the signal. The amount by which the mask increases the signal threshold is plotted and this is repeated for different signal frequencies displayed on the X axis. The frequency of the mask is kept constant. The masking effect is represented in each diagram at different masking sound levels. Narrowband noise is reproduced via upper or inserted headphones. The noise level indicated by the headphones is calculated by the hearing care professional according to BS EN ISO 389-4 or by using masking sounds (M) + 10.

M is the lowest masking level the customer can detect and is measured in dB. Since multiple masking intensities are usually correct, experienced audiologists are advised to use the masking aid without indicating the recommended level of masking. Although clinicians often do not use masking for bone conduction if the air-to-bone distance in the best ear is less than 15 dB, it may be recommended to apply masking to make the measurement specific to the ear. Although an experienced clinician disagrees, wearing a mask in these cases will recommend that masking be necessary. This figure illustrates such a situation. Gray indicates that Masking Assist is not active. Green indicates that the masking was applied correctly. Interacoustic auto-masking is available to reduce the effort required to mask with the correct masking levels.

When auto-masking is enabled, channel 2 is controlled by the system and set to the appropriate intensity level. Auditory masking in the frequency domain is called simultaneous masking, frequency masking, or spectral masking. Auditory masking in the time domain is called time masking or non-simultaneous masking. Auditory masking occurs when the perception of one sound is affected by the presence of another sound. [1] Clinical masking in audiology refers to the introduction of noise into the ear not tested during a tonal audiogram. This is to ensure that the test ear hears the sound presented and is not “heard” by the untested ear. Cross-hearing occurs when a sound presented to the test ear overcomes interaural attenuation, which refers to the loss of acoustic energy as sound waves travel transcranial to the contralateral ear. The sound presented can then be perceived by the untested ear cochlea and lead to false positive results.

This is less likely to occur when testing the airline via plug-in headphones than with supraaural headphones, as plug-in headphones result in increased interaural attenuation. [3] Auditory masking is used to perform data compression for sound signals (MP3). Auto-masking is enabled by selecting the icon that displays the mask with the letter A. For applications, the results of Killion et al. (1985), König (1962) and Sklare & Denenberg (1987) found mean interaural attenuation values of about 80 dB with minimum levels of 70 dB. Therefore, a doctor can use 70 dB during masking. However, most clinicians use a much more conservative 60 dB for deployments. The interaural attenuations used by the masking aid are frequency specific and can be adjusted during setup. The following table lists the standard interaural attenuation (IaA) values.