Distortion product otoacoustic emissions in an industrial setting

Abstract

Distortion product otoacoustic emissions (DPOAEs) is an objective sensitive test of cochlear function. The aim of this study was the evaluation of noise-induced hearing loss in a group of industrial workers, using this method in conjunction with standard puretone audiometry (PTA). One hundred and five subjects (210 ears) were included in the study. PTA, tympanometry, and DPOAEs were performed. Results were analyzed using a mixed analysis of variance model, and compared with the data of 34 normal persons of similar age and sex. We found statistically significant lower DPOAE levels in the noise-exposed group than in the control group. Additionally, the effect of frequency was significant, indicating that amplitude varied across frequency, with lower responses observed at 4 and 6 kHz, and maximum response found at 2 kHz. PTA showed a statistically significant effect of Group, owed to elevated puretone thresholds in the noise-exposed subjects, but a Frequency main effect was not found, although the interaction between Frequency and Group was statistically significant, as well as the interaction between Frequency and Ear. A main effect for Ear was found only in puretone thresholds, due to better thresholds in the left ears of the subjects, and not in DPOAE measurements. DPOAE levels were selectively affected at the higher frequencies, whereas puretone thresholds were affected at all frequencies. Direct comparison of the number of significantly affected ears between the two methods at 1, 2, and 4 kHz showed statistically significant differences at all comparisons, with more ears affected in PTA in comparison with DPOAEs at 4 kHz, whereas more ears were affected in DPOAEs at the lower frequencies (1 and 2 kHz). Therefore, it may be concluded that DPOAEs and PTA are both sensitive methods in detecting noise-induced hearing loss, with DPOAEs tending to be more sensitive at lower frequencies.

Conventional Audiometry, Extended High-Frequency Audiometry, and DPOAE for Early Diagnosis of NIHL

“…In the current study, DPOAE at high frequencies (3000, 4000, and 6000 Hz) was more sensitive to noise than conventional audiometry which was consistent with the results of some studies (20, 26-29). In comparison of conventional audiometry and low-tone DPOAE (1000 and 2000 Hz), our study failed to show a significant difference between the two methods for detection of hearing loss, but Kores et al and Oeken et al found low-tone OAE to be more sensitive than high-tone DPOAE and conventional audiometry for detection of hearing loss (23, 25). Plinkert found TEOAE to be more sensitive than convention audiometry for detection of TTS (24).…”

“…Plinkert et al found that TEOAE is the most sensitive test for the diagnosis of TTS in comparison to DPOAE and PTA (24). Kores et al found that DPOAE is more sensitive than PTA at low frequencies (25). Other studies have also found DPOAE as a more sensitive test than conventional audiometry for the diagnosis of NIHL (20, 26-29).…”

Evoked otoacoustic emissions in workers exposed to noise: A review

“…The occupational categories included were: musicians15 16 17, fishermen18, farmers12, construction workers19 20, military personnel21, textile industry workers22, workers in various industrial activities23 24 25 26 27, university employees exposed to occupational noise4, carpenters4, aviation employees28, mariners29, aviators30, and workers exposed to noise31 (Table 1). …”

“…Of the 12 international papers in the Medline database, 6 used DPOAE24 25 19 20 27 30 and 6 used both tests18 28 21 12 29 17 13 26.…”

“…In the Medline database, although the values L1 = 65 dB SPL and L2 = 55 dB SPL were also used26, there is a wide variation of stimulus intensities21 23 25 26 27 29.…”