The effect of hearing protection on narrowband signal detection in industrial noise.
A method for evaluating the effectiveness of insert protectors at suprathreshold intensities was developed. Normal listeners and workers with clinically diagnosed, bilateral, noise-induced hearing loss attempted to detect a 1 or 3 kHz narrowband signal, 500 msec in duration. The signal was presented binaurally over headphones, either in quiet or against a background of industrial noise taped on site. The level of the noise was fixed at 84 dBA. The level of the signal was varied across blocks of 50 trials from near threshold to clearly audible. Comparisons were made between the detectability of the signal when insert protectors were worn, and listening without protection. The results indicated that in both normal and hearing impaired listeners the slopes of the psychometric functions were fairly steep, covering a range of only about 5 dB. The value of attenuation of the insert protector derived from the displacement of the function for listening in quiet with the protector, relative to listening with the open ear was constant throughout the range of suprathreshold signal intensities used. In 84 dBA of background noise normal subjects showed an improvement of about 3 dB when they wore protectors. By contrast the wearing of protectors in noise by hearing impaired listeners resulted in substantial decrements in signal detection.
D001299:Audiometry; D001309:Auditory Threshold; D004430:Ear Protective Devices; D006317:Hearing Loss, Noise-Induced / Q000175:diagnosis; D006801:Humans; D009622:Noise; D009623:Noise, Occupational; D011482:Protective Devices