Wei Qiu

Publications (22) View all

• Article: The value of a kurtosis metric in estimating the hazard to hearing of complex industrial noise exposures.

  Wei Qiu, Roger P Hamernik, Robert I Davis
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  ABSTRACT: A series of Gaussian and non-Gaussian equal energy noise exposures were designed with the objective of establishing the extent to which the kurtosis statistic could be used to grade the severity of noise trauma produced by the exposures. Here, 225 chinchillas distributed in 29 groups, with 6 to 8 animals per group, were exposed at 97 dB SPL. The equal energy exposures were presented either continuously for 5 d or on an interrupted schedule for 19 d. The non-Gaussian noises all differed in the level of the kurtosis statistic or in the temporal structure of the noise, where the latter was defined by different peak, interval, and duration histograms of the impact noise transients embedded in the noise signal. Noise-induced trauma was estimated from auditory evoked potential hearing thresholds and surface preparation histology that quantified sensory cell loss. Results indicated that the equal energy hypothesis is a valid unifying principle for estimating the consequences of an exposure if and only if the equivalent energy exposures had the same kurtosis. Furthermore, for the same level of kurtosis the detailed temporal structure of an exposure does not have a strong effect on trauma.
  The Journal of the Acoustical Society of America 05/2013; 133(5):2856-66. · 1.55 Impact Factor
• Article: The use of the kurtosis metric in the evaluation of industrial noise exposures.

  Roger Hamernik, Wei Qiu, Robert Davis
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  ABSTRACT: Data from a chinchilla model of noise-induced hearing loss will demonstrate the value of using the statistical metric, kurtosis, along with an energy metric to evaluate complex industrial noise environments for hearing conservation purposes. Complex noises are non-Gaussian noises consisting of a combination of Gaussian continuous noise and noise transients, either impacts or noise bursts. Chinchillas were exposed to an interrupted and intermittent 97-dB sound pressure level broadband, non-Gaussian noise for 8 h∕day for 3 weeks. The experimental noises were designed to model an industrial exposure. Groups of animals with 8∕group were exposed to 1 of 12 different complex noise environments having a fixed spectrum and energy but with different temporal structures achieved by varying the transient peak, interval, and duration histograms. Preliminary results show that (1) hearing and sensory cell loss increase with increasing kurtosis despite a fixed energy; (2) at a given value of kurtosis, hearing trauma is invariant with respect to changes in the temporal structure of the noise exposure. A metric such as the kurtosis may be a necessary adjunct to spectral energy in the evaluation of industrial noise exposures for the purposes of hearing conservation. [Research supported by NIOSH Grant R01 OH 002317.].
  The Journal of the Acoustical Society of America 10/2010; 128(4):2456. · 1.55 Impact Factor
• Article: Application of the kurtosis statistic to the evaluation of the risk of hearing loss in workers exposed to high-level complex noise.

  Yi-Ming Zhao, Wei Qiu, Lin Zeng, Shan-Song Chen, Xiao-Ru Cheng, Robert I Davis, Roger P Hamernik
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  ABSTRACT: Develop dose-response relations for two groups of industrial workers exposed to Gaussian or non-Gaussian (complex) types of continuous noises and to investigate what role, if any, the kurtosis statistic can play in the evaluation of industrial noise-induced hearing loss (NIHL). Audiometric and noise exposure data were acquired on a population (N = 195) of screened workers from a textile manufacturing plant and a metal fabrication facility located in Henan province of China. Thirty-two of the subjects were exposed to non-Gaussian (non-G) noise and 163 were exposed to a Gaussian (G) continuous noise. Each subject was given a general physical and an otologic examination. Hearing threshold levels (0.5-8.0 kHz) were age adjusted (ISI-1999) and the prevalence of NIHL at 3, 4, or 6 kHz was determined. The kurtosis metric, which is sensitive to the peak and temporal characteristics of a noise, was introduced into the calculation of the cumulative noise exposure metric. Using the prevalence of hearing loss and the cumulative noise exposure metric, a dose-response relation for the G and non-G noise-exposed groups was constructed. An analysis of the noise environments in the two plants showed that the noise exposures in the textile plant were of a Gaussian type with an Leq(A)8hr that varied from 96 to 105 dB whereas the exposures in the metal fabrication facility with an Leq(A)8hr = 95 dB were of a non-G type containing high levels (up to 125 dB peak SPL) of impact noise. The kurtosis statistic was used to quantify the deviation of the non-G noise environment from the Gaussian. The dose-response relation for the non-G noise-exposed subjects showed a higher prevalence of hearing loss for a comparable cumulative noise exposure than did the G noise-exposed subjects. By introducing the kurtosis variable into the temporal component of the cumulative noise exposure calculation, the two dose-response curves could be made to overlap, essentially yielding an equivalent noise-induced effect for the two study groups. For the same exposure level, the prevalence of NIHL is greater in workers exposed to non-G noise environments than for workers exposed to G noise. The kurtosis metric may be a reasonable candidate for use in modifying exposure level calculations that are used to estimate the risk of NIHL from any type of noise exposure environment. However, studies involving a large number of workers with well-documented exposures are needed before a relation between a metric such as the kurtosis and the risk of hearing loss can be refined.
  Ear and hearing 08/2010; 31(4):527-32. · 2.06 Impact Factor
• Article: Role of the kurtosis statistic in evaluating complex noise exposures for the protection of hearing.

  Robert I Davis, Wei Qiu, Roger P Hamernik
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  ABSTRACT: To highlight a selection of data that illustrate the need for better descriptors of complex industrial noise environments for use in the protection of hearing. The data were derived using a chinchilla model. All noise exposures had the same total energy and the same spectrum; that is, they were equal energy exposures presented at an overall 100 dB(A) SPL that differed only in the scheduling of the exposure and the value of the kurtosis, beta(t), a statistical metric. Hearing thresholds were determined before and after noise exposure using the auditory-evoked potential measured from the inferior colliculus in the brain stem. Cochlear damage was estimated from sensory-cell counts (cochleograms). (1) For equivalent energy and spectra, exposure to a high-kurtosis, non-Gaussian noise produced substantially greater hearing and sensory-cell loss in the chinchilla model than a low-kurtosis, Gaussian noise. (2) beta(t) computed on the amplitude distribution of the noise could clearly differentiate between the effects of Gaussian and non-Gaussian noise environments. (3) beta(t) can order the extent of the trauma as determined by hearing thresholds and sensory-cell loss. The noise level in combination with the statistical properties of the noise quantified by beta(t) clearly differentiate the effects between both continuous and interrupted and intermittent Gaussian and non-Gaussian noise environments. For the same energy and spectrum, the non-Gaussian environments are clearly the more hazardous. The use of both an energy and kurtosis metric can better predict the hazard of a high-level complex noise than the use of an energy metric alone (as is the current practice). These results point out the need for a new approach to the analysis and quantification of industrial noise for the purpose of hearing conservation practice.
  Ear and hearing 09/2009; 30(5):628-34. · 2.06 Impact Factor
• Article: The effectiveness of N-acetyl-L-cysteine (L-NAC) in the prevention of severe noise-induced hearing loss.

  Roger P Hamernik, Wei Qiu, Bob Davis
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  ABSTRACT: Three groups of chinchillas were exposed to a nonGaussian continuous broadband noise at an Leq=10 5dB SPL, 8h/d for 5d. One group (N=6) received only the noise. A second group (N=6) received the noise and was additionally treated with L-NAC (325 mg/kg, i.p.). Treatment was administered twice daily for 2d prior to exposure and for 2d following the exposure. During exposure the animals received the L-NAC just prior to and immediately after each daily exposure. The third group (N=4) was exposed to the noise and received saline injections on the same schedule as the L-NAC treated animals. Auditory evoked potential recordings from the inferior colliculus were used to estimate pure tone thresholds and surface preparations of the organ of Corti quantified the sensory cell population. In all three groups PTS exceeded 50 dB at 2.0k Hz and above with severe sensory cell loss in the basal half of the cochlea. There was no statistically significant difference among the three groups in all measures of noise-induced trauma. Treatment with L-NAC did not reduce the trauma produced by a high-level, long duration, broadband noise exposure.
  Hearing Research 06/2008; 239(1-2):99-106. · 2.70 Impact Factor