Noise exposure and risk of hearing loss for Air Force welders

Abstract

Recent United States Air Force (USAF) studies hypothesized current measurement techniques are not adequately measuring welder noise exposures, and that welders are losing their hearing at a higher rate than expected based on attributable risk. The objectives of this study were to assess Electromagnetic Field (EMF) interference on welding noise exposure measurements and to assess noise measurement sampling rates and averaging times to determine potential differences in the amount of total energy characterized during routine exposure assessments. Seven types of welding (shielded metal arc welding, gas metal arc welding, gas tungsten arc welding, flux core arc welding, oxy-fuel gas cutting, plasma arc cutting and air carbon arc gouging) were evaluated. Data were collected via a two-channel system using a microphone, pre-amplifier and front-end unit for each channel. The signals were saved to digital audiotape or a digital oscilloscope and then analyzed with a real time analyzer and the digital oscilloscope. One channel was used normally and the other was varied by three methods to evaluate the EMF interference effects. Sampling rates up to 25 MHz were used to collect exposure data. Two of the three methods for evaluating EMF interference were effective. An inactivated calibrator provided 10 to 15 dBA of attenuation and was effective at attenuating noise from 500 Hz to 16 kHz. For this objective, some EMF interference was present, but it did not have an appreciable effect on the measurements. For the second objective, increasing sampling rate did not increase the amount of energy measured and hence the dose did not increase. The results of this study point to investigating additional avenues to explain the hearing loss of the welders. Other possible explanations include: ototoxins, non-occupational exposure, other noise sources, inadequate use of hearing protection or data anomalies in the audiograms.