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Journal of the Acoustical Society of America

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Jun 2011

Volume 129, Issue 6, pp. EL217-4101

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Frequency shifts with age in click-evoked otoacoustic emissions of preterm infants

Sander W. J. Ubbink, Pim van Dijk, Emile de Kleine, Patrick Brienesse, Michelene N. Chenault, Frans E. S. Tan, and Lucien J. C. Anteunis

J. Acoust. Soc. Am. Volume 129, Issue 6, pp. 3788-3796 (2011); (9 pages)

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A previous study [Brienesse et al. (1997). Pediatr. Res. 42, 478–483] demonstrated a positive shift with increasing postmenstrual age (PMA) in the frequencies of synchronized spontaneous otoacoustic emissions (SSOAEs) in preterm infants. We used a mixed model approach to describe a shift with PMA in the spectra of click-evoked otoacoustic emissions (CEOAEs) measured in a group of 22 preterm infants. The rate in shift in CEOAE spectral components was found to be frequency dependent, with a mean estimate of 10 Hz/week for frequencies around 2 kHz and 30 Hz/week for frequencies around 4.25 kHz. This rate decreased with increasing PMA. Because SSOAEs are often part of the CEOAE response, a comparison was made between the shifts in SSOAEs and CEOAEs in a sub-group of 16 preterm infants. The results indicate that the shifts found for both types of OAE are similar, which supports a common mechanism for this change in OAE-characteristic. At present it is not clear to what extent developmental processes in the cochlea and the middle ear can account for these frequency shifts in the spectra of CEOAEs and SSOAEs during the preterm period.
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43.64.Jb Otoacoustic emissions

Human cochlear tuning estimates from stimulus-frequency otoacoustic emissions

Thomas Bentsen, James M. Harte, and Torsten Dau

J. Acoust. Soc. Am. Volume 129, Issue 6, pp. 3797-3807 (2011); (11 pages) | Cited 6 times

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Two objective measures of human cochlear tuning, using stimulus-frequency otoacoustic emissions (SFOAE), have been proposed. One measure used SFOAE phase-gradient delay and the other two-tone suppression (2TS) tuning curves. Here, it is hypothesized that the two measures lead to different frequency functions in the same listener. Two experiments were conducted in ten young adult normal-hearing listeners in three frequency bands (1-2 kHz, 3-4 kHz and 5-6 kHz). Experiment 1 recorded SFOAE latency as a function of stimulus frequency, and experiment 2 recorded 2TS iso-input tuning curves. In both cases, the output was converted into a sharpness-of-tuning factor based on the equivalent rectangular bandwidth. In both experiments, sharpness-of-tuning curves were shown to be frequency dependent, yielding sharper relative tuning with increasing frequency. Only a weak frequency dependence of the sharpness-of-tuning curves was observed for experiment 2, consistent with objective and behavioural estimates from the literature. Most importantly, the absolute difference between the two tuning estimates was very large and statistically significant. It is argued that the 2TS estimates of cochlear tuning likely represents the underlying properties of the suppression mechanism, and not necessarily cochlear tuning. Thus the phase-gradient delay estimate is the most likely one to reflect cochlear tuning.
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43.64.Jb Otoacoustic emissions
43.64.Kc Cochlear mechanics

Is it necessary to penalize impulsive noise +5 dB due to higher risk of hearing damage?

Miguel Angel Aranda de Toro, Rodrigo Ordoñez, Karen Reuter, and Dorte Hammershøi

J. Acoust. Soc. Am. Volume 129, Issue 6, pp. 3808-3817 (2011); (10 pages)

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It is studied whether the +5 dB penalty for impulsiveness established by ISO 1999:1990 accounts for a higher risk of noise-induced hearing loss. A total of 16 normal-hearing human subjects were exposed for 10 min to two types of binaural industrial-recordings: (1) a continuous broad-band noise normalized to LEX,8 h = 80 dBA and (2) the combination of the previous stimulus with an impulsive noise normalized to LEX,8 h = 75 + 5db penalty = 80 dBA (peak level 117 dBC and repetition rate of 0.5 impacts per second). Distortion product otoacoustic emissions (DPOAEs) were measured in a broad frequency range before and in the following 90 min after the exposure. The group results show that the continuous exposure had a bigger impact on DPOAE levels, with a maximum DPOAE shift of approximately 5 dB in the frequency range of 2–3.15 kHz during the first 10 min of the recovery. No evident DPOAE shift is seen for the impulsive + continuous stimulus. The results indicate that the penalty overestimated the effects on DPOAE levels and support the concept that the risk of hearing loss from low-level impulses may be predicted on an equal-energy basis.
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43.64.Jb Otoacoustic emissions
43.64.Wn Effects of noise and trauma on the auditory system
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