Temporary threshold shift is a fancy way of saying that someone experienced short-term hearing loss from exposure to loud noise. The noise source can be instantaneous or prolonged.
Here are five findings from original research by Hallowell Davis on temporary threshold shift:
- Higher frequencies (ex 2-4 kHz) cause a more significant threshold shift than low frequencies (ex 500 Hz).
- Half-octave rule: Audiometric frequency region that demonstrated hearing loss occured between half to one octave higher than the stimulus frequency.
- Significant intra- and inter-subject variability. Sheds some light about how we do not fully understand the functions of the sensorineural mechanism of tinnitus.
- Majority of noise notch hearing loss occurred in the 3-6 kHz region. This corroborates with humans who obtain noise notches in this region with exposure to BBN.
- The most fascinating section of this study for me was correlating the ear canal length (and associated resonance) with a noise notch center frequency. I always think of this in terms of music. Instruments with longer tubes have lower frequency resonance. Therefore, someone with a short ear canal length may have a noise notch and associated tinnitus in a relatively higher-pitch region.
DAVIS H, MORGAN CT. Temporary deafness following exposure to loud tones and noise. Laryngoscope. 1946;56:19-21.
Here is a link to updated research on temporary threshold shift: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4988324/