The Characteristics of Tinnitus and Hearing Threshold: In Workers with Noise Induced Hearing Loss from a Hospital Setting / 대한산업의학회지

OBJECTIVES: This study was carried out to define the relationship between the characteristics of tinnitus and hearing threshold (puretone and speech) in workers with noise induced hearing loss (NIHL). METHODS: A total of 189 cases(378 ears) from workers with compensation claims for NIHL during 2004-2009 were investigated. Various factors, including age, work carriers, body mass index (BMI), blood pressure, noise exposure level of worksite hearing threshold, speech discrimination score, pitch match, and loudness of tinnitus were analyzed. RESULTS: The average hearing threshold of all subject was 44.2 dBHL, puretone audiometry thresholds in subjects with tinnitus were lower than the non-tinnitus group (except at 8000 Hz). Using speech audiometry, the tinnitus group showed a lower speech recognition threshold and speech discrimination score. The tinnitus group also had an average tinnitus frequency of 4195.2 Hz, loudness of 73.6 dB, and tinnitus sensation average of 6.0 dBSL. These frequencies of tinnitus were in the lowest puretone audiometry frequencies. Tinnitus loudness had a strong relationship with puretone and speech audiometry thresholds. CONCLUSIONS: In cases beyond moderate hearing loss, the tinnitus group had a better puretone (except 8000 Hz) and speech hearing status, and most comfortable loudness (MCL) level. In addition, puretone and speech audiometry thresholds increase with tinnitus loudness.

Effects of Workplace Noise and Hearing Protective Devices on Worker's Speech Intelligibility / 대한산업의학회지

OBJECTIVE: The objective of this study was to evaluate the degree of intelligible speech in workers wearing hearing protective devices and the differences in background noise type. METHODS: A total 82 shipyard company employees and normal hearing volunteers were recruited as subjects from a company in Ulsan: subjects were classified to the hearing-impaired group or to the control group according to hearing status. They were tested pure tone and speech audiometry in varying test environments including signal-to-noise ratio and background noise type in a headphone and in a free field environment. RESULTS: For both groups, the attenuation of hearing protective devices was greater at high frequencies. For the hearing-impaired group, speech discrimination scores differences between the unprotected and the protected ear were not significant between background noise type, when speech was presented at 65 dBA. However speech intelligibility in white noise background was lower than in the other background noise types when speech was presented at 75 dBA. CONCLUSIONS: Workers' speech intelligibility increased with an increasing signal-to-noise ratio. Speech intelligibility was also dependent on background noise type. Workers and their colleagues were trained to pronounce words more loudly and more clearly when they wearing hearing protective devices or other communication methods that do not use sound signal should be considered.

The Impact of Noise Expose on the Hearing Threshold Extended High Frequency / 대한산업의학회지

OBJECTIVES: To determine how extended high frequency is affected by noise exposure and other factors that maybe have adverse effects. METHODS: Pure tone audiometry for usual frequencies (250-8000 Hz) and extended high frequencies (1000-16000 Hz) was conducted for 331 workers at a manufacturing company from 2004 to 2005. History of noise exposure, military service, tinnitus, alcohol drinking, smoking, ear diseases, and noisy hobbies were taken by interview. T-test, ANOVA, and multiple regression was conducted according to the frequency to evaluate the factors that could affect extended high frequency hearing. RESULTS: The noise-exposed group had significantly poorer hearing than the noise-unexposed in the frequency range 2000-16000 Hz. The hearing deteriorated with increasing age through all the frequencies. High frequency hearing of 14000 Hz was significantly worse in the noise-exposed group in their 30s. Noise exposure during military service had a bad effect on hearing, especially for the noise-unexposed group. Tinnitus was associated with poorer hearing in both noise-exposed and noise-unexposed groups. Workers with noisy hobbies exhibited better hearing in the noise-unexposed group, contrary to our expectation. Extended high-frequency hearing was affected by aging, ear protection, and noisy hobbies. In extended high frequency, 14000 Hz was especially related with noise exposure history. CONCLUSIONS: Extended high frequency, especially 14000 Hz, could be used as an indicator of noiseinduced hearing loss and should be considered as a screening test for workers in noisy environments.