The Significance of Audiometric Notching in Individuals With a History of Noise Exposure: A Systematic Review
Ear and Hearing
Meghji, S., & Phillips, J. (2021).
Ear and Hearing, 42(5), 1109-1118.
This systematic review investigates audiometric notching at different frequencies to identify noise-induced hearing loss in a variety of populations exposed to noise.
This review found that the correlation between audiometric notch frequency and noise-induced hearing loss (NIHL) varied in different populations of individuals exposed to noise. <br /><br />
<ul>
<li><span style="color: #333333;">Two studies found an isolated 3-kHz notch in orchestra and rock and roll musicians. Other studies investigating notches of mixed frequencies, including the 3-kHz notch, involved children and young adults. The authors found that "there is not enough evidence to link a notch at 3 kHz with NIHL in this current systematic review" (p. 1114). </span></li>
<li><span style="color: #333333;">Individuals regularly exposed to hazardous noise in both intensity and duration (e.g., occupational exposure, industrial exposure, leisure exposure) demonstrated 4-kHz notching. The authors note that many of the studies investigating the 4-kHz notch failed to investigate the possible presence of notches at other frequencies.</span></li>
<li><span style="color: #333333;">Two studies found 6-kHz notches in the majority of electric transmission workers. Several other studies found the 6-kHz notch in other industrial employees (e.g., hydroelectric plant, drop forge hammering), individuals exposed to blasts, and orchestra musicians. The authors note that the 6-kHz frequency on a pure-tone audiogram demonstrates amplified variability compared to other frequencies, so they caution that the 6-kHz notch may be overestimated and produce a false notch.</span></li>
</ul>
While 3- and 6-kHz notches may correlate with noise exposure, some studies also found that notches can be present without noise exposure and may relate to other risk factors (e.g., gender, increasing age, smoking). "Notches observed at 6kHz, unilateral notches, and notches in the absence of continued high-intensity noise exposure must be scrutinized thoroughly" (p. 1116). The authors conclude that more research on the correlation between audiometric notches and NIHL is needed.
