Improvement of speech articulation in a noisy environment by wearing earplugs

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This research was undertaken because of the theory that speech articulation in a noisy environment might be improved by wearing earplugs because earplugs could decrease the level of a specific range of a frequency composition of the noise.First, monosyllable articulation tests were carried out in an environment which was dominated by high frequency components with the variable of whether subjects wore JIS Type 2 earplugs or not. In these tests, sound pressure levels of the noise were set to levels between 65 dB and 85 dB, and sound pressure levels of monosyllables were set to levels between 0 dB and -10dB which referred the sound pressure level of the noise, that is, signal to noise ratios were between 0 and -10 dB. The results showed that the monosyllable articulations did not relate to wearing earplugs.Next, on the assumption of hard environmental noise, monosyllable articulation test was carried out exposing white noise of 95 dB SPL. In this test, monosyllables were set to 90 dB SPL, that is, signal to noise ratio was -5dB. In the noise at this sound pressure level, the acoustic reflex must be caused. In this test, JIS Type 1 earplugs which can insulate broad band sound were used. The results showed that monosyllable articulation obviously improved when the subjects wore earplugs.The conclusions of this research are as follows.1.In the noise of sound pressure level in which the acoustic reflex is caused, our hearing system can be protected by wearing earplugs, moreover, our speech articulation can be improved.2.In the noise of sound pressure level that is lower than the situation above, the difference of the speech articulation by wearing earplugs is not observed. This means that the speech articulation doesn't decrease even if the subject wears earplugs.