OBJECTIVETo compare the dose-response relationship differences between impulse noise exposure workers and continuous noise exposure workers in prevalence of noise inducing hearing loss using dosimeter measurement.

METHODSThirty-two mechanical workers in a workshop were selected as impulse noise group and 163 textile workers in a textile factory as continuous noise group. SH-126 dosimeter was used to measure A weighted equal sound level of eight hours (L(Aeq.8 h)) during full working duration with equal energy rule for the selected workers. The cumulative noise exposure (CNE) was calculated by L(Aeq.8 h) and noise working years with equal energy rule for each worker. Hearing thresholds were measured by audiometer by routine method and adjusted by age and gender with GBZ49 - 2002. Hearing loss was diagnosed by GBZ49 - 2002 for each worker.

RESULTSCNE of impulse noise group [(103.2 +/- 4.2) dB (A) .year] was found lower than the continuous noise group [(110.6 +/- 6.0) dB (A) .year] by significance, P < 0.05. The hearing loss prevalence of impulse noise group (68.8%) was similar as continuous noise group (65%) without significance, P > 0.05. Strata analysis showed the hearing loss prevalence in 100 - 104 dB (A) .year and 105 - 109 dB (A) .year of impulse noise group was double than that of continuous noise group (76.9%, 90.9% vs 30.4%, 50.0%), P < 0.05. The chi-square test showed a relationship between CNE and hearing loss prevalence that was in high significance (P < 0.01) in both impulse noise group and continuous noise group. Logistic regression model showed the dose-response relationship curve of impulse noise group was left shift and sharp slope.

CONCLUSIONThe damage of impulse noise on hearing loss was much more than that of continuous noise according to equal energy rule of dosimeter data.