Redefining standards for high-energy impulse noise in the workplace

Noise-induced hearing loss (NIHL) is among the most prevalent forms of occupational illness, with nearly one-third of industrial workers in China at risk. While most guidelines focus on total energy of occupational noise, assuming Gaussian distributions, modern industrial noise is often composed of high-energy impulses. Such noise occurs with very little crescendo and decrescendo, causing their volume distributions to be highly kurtotic, steeping more suddenly than a normal Gaussian curve.

Researchers have evaluated the excess risk posed by high-kurtosis noise among Chinese industrial workers. Using two evaluative metrics, Qiu et al. completed a cross-sectional analysis of 3421 workers’ low- and high-frequency hearing loss.

Their analysis used second-order derivatives of excess risk curves to derive occupational exposure limits (OELs) specifically for settings where high-kurtosis noise is expected to occur.

“Previous research introduced kurtosis-adjusted cumulative noise exposure and logistic regression modeling but stopped short of integrating these into quantitative standards,” said author Wei Qiu. “By converting model derivatives into practical exposure limits, the study bridges the gap between epidemiological modeling and regulatory guidance.”

They found that excess risk increased with increasing kurtosis, in addition to other factors including worker age, gender, and exposure duration. The group then derived OELs of 80 A-weighted decibels (dBA) for low-frequency and 77 dBA for high-frequency noise, with an additional 2 dB reduction recommended in workplaces where sudden noises with kurtosis values of 70 or more are likely to occur.

“The study provides compelling evidence that equal-energy-based OELs are insufficient for modern industrial noise,” said Qiu. “Because complex noise is common and high-kurtosis exposures aggravate early NIHL, regulators may adopt lower permissible limits or incorporate kurtosis penalties.”

Source: “Evaluation of the risk of noise-induced hearing loss and the significance of occupational noise exposure limit among Chinese industrial workers,” by Hengjiang Liu, Meibian Zhang, Xin Sun, Weijiang Hu, Shixing Bai, Zou Hua, Dandan Zhang, Beibei Lu, Yu Tian, Jingsong Li, and Wei Qiu, The Journal of the Acoustical Society of America (2025). The article can be accessed at https://doi.org/10.1121/10.0038801 .