Effect of Frequency and Duration on Threshold
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Date
2011-06
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The Ohio State University
Abstract
Noise Induced Hearing Loss (NIHL) is caused by repeated exposure to intense sounds or a short-term exposure to an extremely intense sound, and cannot be reversed or treated. The purpose of this experiment was to develop a test to reliably detect an early onset of NIHL. This specific research covered only the baseline, or the normal hearing results that are going to be used in future experiments involving subjects with mild and moderate NIHL. Past research has shown that individuals with NIHL have a much flatter temporal integration curve (the decrease of threshold with the increase of sound duration) than their normal hearing counterparts. If the most affected frequency is not known, the test can be modified to use brief tones that change in frequency and duration. This is called spectrotemporal integration. Normal hearing subjects do well with longer duration sounds that change in frequency over time, while subjects with NIHL do much better with short bursts perhaps because their brain will interpret each burst as a new sound. Five normal hearing young adult listeners were asked to sit in a sound booth and press “yes” or “no” button when they decided whether they heard a sound or not. Three experimental conditions were used: Temporal Integration (the same frequency at different durations), and two Spectrotemporal Integration conditions: Step (the frequency jumps rapidly in a stair-like pattern with duration), and Linear (the frequency changes gradually with time). The results showed that there is a definite threshold improvement with duration, but it is not clear whether one task is better at improving threshold than and the other two tasks.
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Keywords
brief tone audiometry, Noise-Induced Hearing Loss, audiology, NIHL, Hearing Loss