• The Journal of the Acoustical Society of Korea
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• v.32 no.5
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• pp.423-429
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• 2013

The present study aimed to find the most sensitive placement of the skull to perceive speech through the bone vibrator in various protection methods while being exposed to noise. Twenty young normal-hearing adults (10 male and 10 female) participated in the study. As stimulus, Korean spondee words were presented via one of five skull locations (i.e., jaw angle, condyle, temple, mastoid, and vertex), while the participants wore one of four protection methods (i.e., ear form, ear plug, ear muff, and ear form and muff together) against white noise in one of four noise directions (i.e., 0, 90, 180, 270 degrees). The results showed: 1) there was a significant difference among the five skull locations with condyle being the most sensitive placement; 2) there was a significant difference among the four protection methods, with the ear form plus ear muff condition (or dual protection) providing the lowest threshold; 3) when exposed to noise from 90 degrees, the significantly lowest threshold was found; 4) there was no significant difference in results by gender. The pattern of results suggests that the communicative condition via the condyle bone conduction and the dual protection of the air conduction under any noise direction might be ideal for preventing noise-induced hearing loss, although further studies should be undertaken in this area.

• The Journal of the Acoustical Society of Korea
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• v.30 no.4
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• pp.207-214
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• 2011

Human auditory acuity decreases naturally due to aging. But recently cases of impaired hearing at a young age are increasing greatly. The biggest reason for such an increase of population with impaired hearing is popularization of various kinds of portable multimedia appliances. Many studies on impaired hearing due to noises caused by the earphone and headphone are being made, but there are few studies on noise-impaired hearing caused directly by mobile phone communication. Based on a precedent inquiry, this study proposes a technique for preventing noise-impaired hearing applying to an active noise reduction technique onto bone conduction speaker. This technique is a method for reducing noises by antiphase oscillation through bone conduction speaker with ambient noises. If the proposed system is applied, the noise level that is actually introduced to audition decreases by more than 12 dB, and such a decreased amount of sound volume fundamentally prevents the factors of noise-caused hearing difficulty due to mobile phone communication. Sensibility test results showed that adequate communication was possible even in such a situation where communication volume was decreased like this.

• Journal of Digital Convergence
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• v.14 no.4
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• pp.363-370
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• 2016

Noise is unwanted sound that is the reason of the stress and hearing loss. The current study attempted to estimate whether the noise of dental laboratory affected stress and pure tone audiometry (PTA) of dental laboratory technicians (DLTs) using heart rate variability, air and bone conduction audiometry. The age, heights, and weights of DLTs were resembled control. Standard deviation of normal to normal interval such as stress resistance and normalized HF of DLTs were significantly decreased, but heart rates, normalized LF, and LF/HF ratio of DLTs were significantly increased compared with control. In air conduction audiometry of DLTs, significant increments of thresholds encountered in 125, 250, 500, 1000, 2000, 3000, 4000, and 6000 Hz in the right ears and 125, 250, 500, 1000, and 2000 Hz in the left ears. Thresholds of bone conduction audiometry in both ears were significantly increased in 250, 500, 1000, 2000, and 4000 Hz. The findings in this study provide that stress and hearing loss observed in noise-exposed DLTs at dental laboratory. Therefore, proper safety precautions should be carried out at dental laboratory.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.3 no.1
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• pp.21-25
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• 2009

Generally, fully implantable middle ear hearing device (F-IMEHD) is implanted under the skin nearby human temporal bone with all components including implantable microphone and vibration transducer. The microphone and transducer have different characteristic before and after implant. Fitting process is performed for this characteristic change of them and proper performance of hearing aids for each patient. Conventional hearing aids and partially implantable hearing aids, they have wired connector for fitting process. However in case of F-IMEHD, it is difficult this wired connection, because all components of F-IMEHD is implanted. In this paper, fitting software that can be apply wireless fitting hardware for F-IMEHD has been designed and implemented. It can find out proper fitting parameter reflecting characteristics of the microphone and transducer for patients who has difficulty in hearing.

• Journal of Preventive Medicine and Public Health
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• v.28 no.4 s.51
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• pp.765-771
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• 1995

This study was performed to investigate the possibility of temporary threshold shift (TTS) of vibration sense could induced by exposure to high-frequency vibration or by work position taking by dentists in drilling or polishing. The vibratory perception thresholds (VPT) of 28 healthy men were measured on the index fingertip pulp of dominant hand at 250 Hz. The vibrating tool used in test was a low-speed handpiece of 34,000 rpm. For the TTS test, the dominant hand was exposed to high-frequency vibration and to work position for five minutes, respectively. The VPTs before and after vibratory exposure were $23.5{\pm}3.5dB,\;30.8{\pm}4.2dB$, respectively and VPT after work position was $23.7{\pm}4.6dB$. The difference between before and after vibartory exposure was statistically significant (p<0.001). The correlation of height, weight and BMI with baseline VPTs was not statistically significant. Also, there was no difference of VPTs by smoking. These results suggest that high-frequency vibration from dental handpieces might cause the impairment of vibration sensation.