Sandblasting in New Zealand: Noise Exposure and Attenuation Provided by Safety Equipment
Degree GrantorUniversity of Canterbury
Degree NameMaster of Audiology
Noise Induced Hearing Loss (NIHL) is a sensorineural hearing loss resulting from excessive noise exposure (von Geirke, 1975). In New Zealand the Department of Labour stipulates that employees must not be exposed to more than an eight-hour equivalent continuous A-weighted sound pressure level (LAeq,8h) of 85 dB(A) or a peak sound pressure level (Lpeak) of 140 dB(A). Sandblasting is a process, whereby an abrasive is mixed with air at high pressures and exposes the operators to excessive noise (Blair, 1975). The protective equipment currently worn is a closed respirator system consisting of a helmet and cape, overseas research indicates noise levels inside the helmet are above the allowable levels (Blair, 1975; Environmental Medicine Unit, 1998; Irving, 1995; Patel and Irvings, 1999; Price and Whitaker, 1986 and Sussel 1992). There is disagreement in the literature as to the contribution of the noise created by the respirator system to the total noise exposure (Blair, 1975; Environmental Medicine Unit report, 1998; Irving, 1995 and Price and Whitaker, 1986). In some blasting sites additional hearing protection such as foam insert earplugs and/or earmuffs are worn in conjunction with the helmet. No research could be found investigating the resulting attenuation these combinations provide. It is well reported in the literature that the combined attenuation is more complex than the simple sum of the two components attenuation (Abel & Armstrong, 1991; Abel & Odell, 2006; Behar, 1990; Berger, 1983; Damongeot, Lataye & Kusy, 1989). The aims of the current study were to investigate noise levels during blasting inside booths and the operators’ helmets at two sites in New Zealand. The attenuation provided by the helmet alone and in combination with earmuffs was investigated in the laboratory. The contribution of the respirator airflow to the total noise exposure was also investigated. Finally the measured combined attenuation was compared to that calculated using three methods from the literature. Findings indicate that noise levels in blasting booths and inside operators’ helmets are above allowable levels. Laboratory findings indicate that the use of earmuffs in conjunction with the helmet increases the attenuation provided, therefore decreasing the risk of NIHL and that noise from the respirator airflow does not contribute to the total noise inside the helmet. The combined attenuation calculated from two methods in the literature was inaccurate while one was close. The findings, recommendations, limitations of the study and areas for further research are discussed.