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The value of a kurtosis metric in estimating the hazard to hearing of complex industrial noise exposures
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10.1121/1.4799813
/content/asa/journal/jasa/133/5/10.1121/1.4799813
http://aip.metastore.ingenta.com/content/asa/journal/jasa/133/5/10.1121/1.4799813

Figures

Image of FIG. 1.
FIG. 1.

The impact interval histograms (I and I), peak amplitude histograms (P and P) and duration histograms (D and D) computed over a 5.5 min digitized segment of the non-Gaussian noise.

Image of FIG. 2.
FIG. 2.

Mean preexposure evoked potential thresholds for all (n = 225) chinchillas compared to laboratory norms (shaded area) based on a sample of 1572 chinchillas.

Image of FIG. 3.
FIG. 3.

(a) The relative spectral level of the 97 dB SPL Gaussian noise. (b) The relative spectral level of the 97 dB SPL nonG, β(t) = 50, noise. The insert shows a representative 40 s sample of the nonG waveform. Both spectra were computed over a 5.5 min sample of the digitized waveform. (c) The relative spectral level of a representative impact noise transient along with the temporal waveform. All the synthesized impacts had similar spectra. The impacts were designed using an exponential decay function. The duration of the impact was taken as the time from the initial peak to the 20 dB down point.

Image of FIG. 4.
FIG. 4.

(a) The octave band Leq of the four β(t) classes of noise used in the exposures. The dotted line represents the A weighted Leq. The data points were computed over a 5.5 min sample of the digitized waveform. (b) The frequency specific kurtosis, β(f), computed on consecutive octave bands of the filtered noise signal for each of the four classes of noise. Each data point represents a value of β(f) computed on consecutive 40 s bins of the filtered 5.5 min waveform and then averaged.

Image of FIG. 5.
FIG. 5.

Group mean (a) permanent threshold shift (PTS), (b) percent inner hair cell loss (%IHC), and (c) percent outer hair cell loss (%OHC) for the eight groups of animals exposed to the interrupted β(t) = 25 nonG noise at 97 dB SPL for 19 d. Symbols refer to the different combinations of the impact noise interval (I), peak (P), and duration (D) histograms used to create the nonG noise (Table I ). The exposure for each group differed only in the I, P, and D histograms used to create the nonG noise.

Image of FIG. 6.
FIG. 6.

Group mean (a) permanent threshold shift (PTS), (b) percent inner hair cell loss (%IHC) and (c) percent outer hair cell loss (%OHC) for the eight groups of animals exposed to the interrupted β(t) = 50 nonG noise at 97 dB SPL for 19 d. Symbols refer to the different combinations of the impact noise interval (I), peak (P) and duration (D) histograms used to create the nonG noise (Table I ). The exposure for each group differed only in the I, P, and D histograms used to create the nonG noise.

Image of FIG. 7.
FIG. 7.

Group mean (a) permanent threshold shift (PTS), (b) percent inner hair cell loss (%IHC), and (c) percent outer hair cell loss (%OHC) for the eight groups of animals exposed to the interrupted β(t) = 100 nonG noise at 97 dB SPL for 19 d. Symbols refer to the different combinations of the impact noise interval (I), peak (P), and duration (D) histograms used to create the nonG noise (Table I ). The exposure for each group differed only in the I, P, and D histograms used to create the nonG noise.

Image of FIG. 8.
FIG. 8.

The averaged (a) permanent threshold shift (PTS), (b) percent inner hair cell loss (%IHC), and (c) percent outer hair cell loss (%OHC) of all groups exposed to the β(t) = 25 (n = 62), 50 (n = 63), or 100 (n = 63) nonG noise at 97 dB SPL for 19 d regardless of the temporal structure of the noise exposure. The mean data (n = 6) from the group exposed to the equivalent energy 19 d Gaussian [β(t) = 3] noise is shown in each panel for comparison.

Image of FIG. 9.
FIG. 9.

The group mean (a) permanent threshold shift (PTS), (b) percent inner hair cell loss (%IHC), and (c) percent outer hair cell loss (%OHC) for groups exposed to the β(t) = 25 (n = 8), 50 (n = 8), or 100 (n = 8) nonG noise at 97 dB SPL for 19 d. All three groups were exposed to the nonG noise having the same IPD temporal structure. The mean data (n = 6) from the group exposed to the equivalent energy 19 d Gaussian [β(t) = 3] noise is shown in each panel for comparison.

Image of FIG. 10.
FIG. 10.

The mean percent (a) outer hair cells (OHC) and (b) inner hair cells (IHC) lost within the 1.0, 2.0, 4.0, and 8.0 kHz octave band region of the basilar membrane for all animals exposed at a fixed β(t) to the 97 dB SPL noise for 19 interrupted days as a function of the frequency specific kurtosis β(f) computed on that octave band [see Fig. 4(b) ].

Image of FIG. 11.
FIG. 11.

The group mean (a) permanent threshold shift (PTS), (b) percent inner hair cell loss (%IHC), and (c) percent outer hair cell loss (%OHC) for the groups exposed to the β(t) = 3, 25, 50, and 100 noise at 97 dB SPL for 5 continuous days. All three nonG groups were exposed to the noise having the same IPD temporal structure.

Image of FIG. 12.
FIG. 12.

The group mean asymptotic threshold shift (ATS) for the groups exposed to the β(t) = 3, 25, 50, or 100 nonG noise at 97 dB SPL for 5 continuous days. All three nonG groups were exposed to the noise having the same IPD temporal structure.

Image of FIG. 13.
FIG. 13.

The mean total number of (a) outer hair cells (OHC) and (b) inner hair cells (IHC) lost for all animals exposed to the 97 dB SPL noise for 19 interrupted days and for 5 continuous days is shown as a function of the kurtosis β(t).

Image of FIG. 14.
FIG. 14.

The mean threshold recovery (Tr) for the groups exposed to the β(t) = 25, 50, or 100 the interrupted nonG noise at 97 dB SPL for 19 days regardless of the temporal structure of the noise exposure. The mean Tr data (n = 6) from the group exposed to the equivalent energy Gaussian [β(t) = 3] noise is also shown for comparison. Note: Tr is the difference between the threshold measured following the first day (T) and the mean of the thresholds measured following the last three days (T) of the interrupted exposure [Tr = (T) – (T)].

Image of FIG. 15.
FIG. 15.

Scatter plots of the individual animal (n = 194) PTS and OHC loss from all the 19 day exposures.

Tables

Generic image for table
TABLE I.

Outline of the 29 groups of animals exposed to the various broadband, 97 dB SPL noise exposures (Σn = 225).

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/content/asa/journal/jasa/133/5/10.1121/1.4799813
2013-05-06
2014-04-17
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: The value of a kurtosis metric in estimating the hazard to hearing of complex industrial noise exposures
http://aip.metastore.ingenta.com/content/asa/journal/jasa/133/5/10.1121/1.4799813
10.1121/1.4799813
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