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Sound attenuators with baffles that break the line of sight or elbow attenuators with a bend provide better high frequency attenuation than conventional lined ductwork. [19] Generally, longer attenuators with thicker baffles will have a greater insertion loss over a wider frequency range. [4]
These options include counseling, amplification, and other assisted listening devices, such as frequency modulation (FM) systems. [134] FM systems can enhance the use of hearing aids and overcome the effects of poor listening conditions because the signal is sent from the microphone worn by the speaker directly to the listener. [ 135 ]
[22] [23] Nevertheless, pharmacological treatment options are very limited and clinically unproven. [24] Such pharmaceutical treatments as are employed are palliative rather than curative, and addressed to the underlying cause if one can be identified, in order to avert progressive damage.
The attenuation in the signal of ground motion intensity plays an important role in the assessment of possible strong groundshaking. A seismic wave loses energy as it propagates through the earth (seismic attenuation). This phenomenon is tied into the dispersion of the seismic energy with the distance. There are two types of dissipated energy:
Real-ear attentuation at threshold (REAT) measurements test how narrowband noises of varying frequency are attenuated with and without the custom mold in place. Testing for low-frequency attenuation can help to verify the earmold fit while testing high-frequency attenuation can verify the properties of the filter used. [6] [21]
Acoustic attenuation in water is frequency-squared dependent, namely =. Acoustic attenuation in many metals and crystalline materials is frequency-independent, namely =. [10] In contrast, it is widely noted that the of viscoelastic materials is between 0 and 2.
In 1957 Willard Meeker developed a working model of active noise control applied to a circumaural earmuff. This headset had an active attenuation bandwidth of approximately 50–500 Hz, with a maximum attenuation of approximately 20 dB. [3] By the late 1980s the first commercially available active noise reduction headsets became available.
Conventional audiometry tests frequencies between 250 hertz (Hz) and 8 kHz, whereas high frequency audiometry tests in the region of 8 kHz-16 kHz. Some environmental factors, such as ototoxic medication and noise exposure, appear to be more detrimental to high frequency sensitivity than to that of mid or low frequencies. Therefore, high ...