Fatigue Modeling via Mammalian Auditory System for Prediction of Noise Induced Hearing Loss

Abstract

Noise induced hearing loss (NIHL) remains as a severe health problem worldwide. Existing noise metrics and modeling for evaluation of NIHL are limited on prediction of gradually developing NIHL (GDHL) caused by high-level occupational noise. In this study, we proposed two auditory fatigue based models, including equal velocity level (EVL) and complex velocity level (CVL), which combine the high-cycle fatigue theory with the mammalian auditory model, to predict GDHL. The mammalian auditory model is introduced by combining the transfer function of the external-middle ear and the triple-path nonlinear (TRNL) filter to obtain velocities of basilar membrane (BM) in cochlea. The high-cycle fatigue theory is based on the assumption that GDHL can be considered as a process of long-cycle mechanical fatigue failure of organ of Corti. Furthermore, a series of chinchilla experimental data are used to validate the effectiveness of the proposed fatigue models. The regression analysis results show that both proposed fatigue models have high corrections with four hearing loss indices. It indicates that the proposed models can accurately predict hearing loss in chinchilla. Results suggest that the CVL model is more accurate compared to the EVL model on prediction of the auditory risk of exposure to hazardous occupational noise.

Figure 1

A schematic diagram of a model of auditory periphery, consisting of external ear, middle ear, and inner ear sections [15].

Figure 2

(a) The gain of the external ear and (b) the transfer function of the middle ear of chinchilla.

Figure 3

Schematic diagram of the TRNL filter, in which the velocities of stapes in middle ear are passed through three parallel branches to obtain the velocities of BM.

Figure 4

Rainflow matrix of BM velocities at the ith ERB in 1 second.

Figure 5

Time-frequency presentations of BM velocities as the output of the TRNL filter, responding to (a) impulsive noise, (b) sweeping chirp noise at low frequency (400–500 Hz), and (c) sweeping chirp noise at high frequency (8000–12000 Hz). The labels of frequency axis indicate the different locations along BM, which refer to the partitions in cochlea.

Figure 6

Time-frequency presentations of the BM velocities obtained by the developed chinchilla auditory model, responding to two experimental noise samples: (a) G63 and (b) G61. The partial waveforms of G63 and G61 in 0.5 sec are shown in the top insert figures. The front views of the distributions of the BM velocities are shown in the bottom insert figures.

Figure 7

Scattering plots and fitting lines of pairs of the developed fatigue metrics, L _EVL (black color) and L _CVL (blue color), and four hearing loss indications (i.e., OHC loss, IHC loss, TTS, and PTS) at six one-octave frequency bands, averaged by all 22 groups of animal experimental data. The p values have been summarized in Table 3.

Figure 8

Regression analysis of averaged OHC₁₂₄₈ and IHC₁₂₄₈ loss and mammal auditory system based fatigue metrics.

Figure 9

Regression analysis of averaged PTS₁₂₄₈ and TTS₁₂₄₈ and mammal auditory system based fatigue models.