Basic studies on the objective evaluation method of noise using the anchor effect.
Current objective methods that estimate noise have a defect in that the measurement values are not stable and the noise can be measured only at pre- and post-exposure times. Some previous studies on the "anchor effect" suggested that noise can be objectively evaluated by evoked potentials (N1 and P2 components), when the noise exposure and the test stimuli to elicit the evoked potentials are given alternately. However, several basic experiments are required to establish this method for noise estimation. The differences in the time durations of stimuli be interchanged with the load of noise were studied in Experiment 1. As a result only N1 latency showed significant differences. This suggested that a continuous tone is suitable for intervening stimuli. In Experiment 2, the relation between evoked potentials and differences in the frequencies of intervening and test stimuli were studied in the wide frequency ranges of 250, 500, 1k, 2k, 4k, and 8k Hz. The results showed a tendency for the frequencies of intervening stimuli to become farther and farther removed from those of the test stimuli as the N1-P2 amplitudes of the latter become larger. This result revealed that pure tones are not suitable for test stimuli; therefore, white noise and pink noise were used as test stimuli in Experiment 3. The amplitude of response induced by white noise was not changed by the frequencies of the intervening stimulus. These results suggested that using evoked potential can be an objective method for noise estimation, when white noise is loaded as a test stimulus after the intervening stimulus.
Hosokawa
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Department of Hygiene and Preventive Medicine, Hokkaido University School of Medicine, Sapporo, Japan.
D000161:Acoustic Stimulation / Q000379:methods*; D000328:Adult; D001921:Brain / Q000502:physiology; D004781:Environmental Exposure; D004784:Environmental Monitoring; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D009622:Noise