## 1 Introduction  
Occupational noise is considered the major cause of noise-induced hearing loss (NIHL), which is sensorineural, usually bilateral, and irreversible with an early sign of \"notching\" at the high frequencies of 3, 4, or 6 kHz of the spectrum [1, 2]. It was estimated that 16% of hearing loss in adults worldwide (over 4 million disability-adjusted life years) was attributed to occupational noise in 2000, with larger proportions in developing countries or regions [3]. To protect workers from hearing impairment or loss, the International Labor Organization (ILO) recommended a warning and a dangerous limits of noise levels of 85 and 90 decibels measured on the A scale (dBA) for time-weighted average (TWA) over an 8 h work shift, respectively [4], and the limits were adopted to be permissible exposure levels (PELs) in the regulations by many countries. Although efforts to minimize the incidence of NIHL have been made in countries around the world, the global burden of NIHL is a significant health issue. According to a recent document of the World Health Organization (WHO), the global improvements on NIHL after the year 2000 were limited as a whole; there were even 27% of countries in the Americas that lacked legislation regarding PELs for occupational noise [5].  
NIHL continues to be a prevalent health issue across a variety of industries, among which woodwork is of concern because of exposure to occupational noise at high levels [6, 7, 8, 9, 10, 11]. An Indian survey showed that 28% of sawmill workers suffered NIHL [7]; a Nepalese cross-sectional study indicated that 31% of carpenters and 44% of sawyers met criteria for NIHL, and the noise levels ranged from 71.2 to 93.9 dBA [11]. A study conducted in small-scale industries of Iran also demonstrated carpentry as one of working environments where the average noise levels were around 85 dBA [8]. Woodwork usually requires use of a number of power tools for sawing, sanding, drilling, and other tasks, which could generate noises at different levels that induced NIHL. Besides personal protective equipment, monitoring of working environments is an effective but not practical approach for assessing noise exposure, because of the inconvenience of wearing personal sampling gear during the 8 h work. If there was an alternative that is easier and more practical than personal noise measurement, performing an assessment of noise exposure could be implemented more smoothly.  
This pilot study attempted to validate an alternative to personal measurement of occupational noise by finding out frequently used woodwork tools, assessing doses and frequency spectra of individual power tools, and integrating noise data generated by individual tools with time periods of tool use. The simulated 8 h TWA noise exposures and frequency spectra by the alternative method matching on-site measurements suggests that noise exposure could be calculated with multiple times of tool use and known noise characteristics of the individual tools. Thus, recording use and operating time of each power tool during the 8 h work could estimate the TWA noise exposure for woodworkers. We expect this alternative method to bring convenience to noise exposure assessment and to facilitate prevention control of occupational noise for woodworkers.