Reflection Of Acoustic Reflexes

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Acoustic reflexes are contractions of the stapedius muscle in the middle ear. This reflex occurs when a loud sound is presented to the ear causing the tympanic membrane to stiffen and cause a change in immittance (Martin & Clark, 2012). When measuring the acoustic reflex threshold, we are measuring the softest sound that can cause a reflex of the stapedius muscle as well as the duration of time needed for the reflex to decay. The reflex is presented as a deflection, or a curve/dip, on the immitance monitor of the device used (Campbell, 2014).
Acoustic Reflex measurements are a part of the immittance battery tests and use the same device as that of tympanometry testing. The reflex occurs by stimulating the stapedius muscle with a loud sound composed of a tone or noise to the ear. Stimulus is usually presented through a 220-226 Hz probe; however, for newborns a higher frequency probe must be used. Acoustic Reflexes have been testes using wideband energy reflectance, but this is not yet used in general clinics (Katz, Medwetsky, Burkard, & Hood, 2002). Katz et al. have also stated that the measurements can be carried out in Sound Pressure Level
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First, introduce the stimulus at 70 dB HL, if there is no response increase intensity by 10 dB until a response is seen. When is response is seen, lower the intensity level by 10 dB and if there is no response increase by 5 dB until a threshold can be determined. The tonal duration should be one second and a response is recorded when a deflection is observed to be a minimum of 0.01 to 0.02 mmho.(Martin & Clark, 2012). It has been observed that when the stimulus is louder, the reflex deflection will be larger(Katz, Medwetsky, Burkard, & Hood, 2002). Normative data has shown that normal ART ranges from 85-100 dB SPL or 80-90 dB HL in pure tone stimuli and is usually approximately 20 dB less in BBN(Katz, Medwetsky, Burkard, & Hood,

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