Development of High-performance Hearing Test System / 中国医疗器械杂志

This paper analyzes the shortcomings of the existing pure tone audiometers, and proposes a system to realize pure tone audiometry and speech audiometry with a new DSP processor. The pure tone test signal produced by the system has accurate frequency, high signal-to-noise ratio, and small harmonic distortion. The noise generator that comes with DSP adds a band-pass filter to realize the generation of narrow-band noise. At the same time, due to the modular structure of software design, the system has good ease of use and scalability. The test results show that the hearing test system has excellent performance and can be better used in hearing medical diagnosis.

Acoustic Calibration of Clinical Audiometers Used for Special Periodic Health Examination / 대한산업의학회지

OBJECTIVES: Various problems are encountered during audiometric testing. Deviation from reference threshold levels for supra-aural earphones is often a serious problem when hearing levels are measured. This paper reports the acoustic calibration of clinical audiometers used for special periodic health examination. METHODS: ANSI S3.6-1996 Specification for Audiometers represents our most current and best resource for information regarding audiometers. The acoustic calibration was measured in 211 clinical audiometers and compared with the ANSI S3.6-1996 reference threshold levels for supra-aural earphones. RESULTS: Among 211 clinical audiometers, 56 (26.5%) exceeded the permitted deviation from reference threshold levels at any test frequency in ANSI S3.6-1996 for left supra-aural earphones, and 54 (25.6%) for right. An exhaustive calibration was required for 16 audiometers (7.6%) in both supra-aural earphones. The absolute difference in dB deviation from reference threshold levels by performed acoustic calibration at least annually were statistically significant at any test frequency (p<.05). CONCLUSIONS: The results of this study strongly indicate that clinical audiometry is being conducted with pure-tone audiometers having unallowable sound pressure levels deviations for supra-aural earphones. The validity of audiometric hearing thresholds are significantly affected by these deviations from the acoustic calibration levels of audiometers. Therefore audiometer calibration need to be checked functionally daily and acoustically at least annually.

Study on Short Term Test-Retest Reliability of High Frequency Audiometry / 대한이비인후과학회지

Although high frequency threshold has been regarded as a early detector of cochlear damage, there has been no standardized system for calibration or measurement of high frequency threshold. Compared measurement of the high frequency(10-20KHz) with measurement of the low frequency(250-8000Hz), it is difficult to establish high frequency normative values because thresholds vary widely with age, calibration system and kinds of audiometer, etc.... But short term test-retest may not be influenced by calibration variance. So we tried to obtain intrasubjective test-retest threshold difference of high frequency threshold difference within 4 weeks intervals. 47 ears of normal low frequency hearing(250-8000Hz) young adults were tested with commercial high frequency audiometer(Beltone 2000) and Sennheiser HD 250 linear headphone. The results were as follows: 1) Test-retest difference within 10dB SPL was more than 89% in every frequency. 2) Test-retest difference within 15dB SPL was more than 96% in every frequency. Results of this study suggest that acceptable range of intrasubjective difference of high frequency threshold within 4 weeks intervals is 15dB SPL.

Application of HHIE-S(Hearing Handicap Inventory for the Elderly-Screening version) to screening test of noise-induced hearing loss / 예방의학회지

The study conducted from May to September in 1994 to investigate applicability of the Hearing Handicap Inventory for the Elderly-Screening version(HHIE-S) in parallel with the puretone audiometer to the initial screening test of noise-induced hearing loss(NIHL) in some noise-exposed workers. Subjects were selected by systemic sampling that took every fifth person from 6,700 workers taking the annual occupational health examination by the department of Health Maintenance of Dongsan Hospital Keimyung University in Taegu. The authors administered the pure-tone audiometric test and self-reported questionnaire of HHIE-S including items of sociodemographic and job-related variables concurrently. The final subjects analysed were 1,019(488 males and 531 females) excluding fourteen persons who had many missing values in their questionnaires. The reliability coefficients of HHIE-S scale by Cronbach's alpha were 0.84. In the univariate analysis of hearing handicap measured by the HHIE-S, work duration, military service and the hearing threshold loss at 1kHz and 4kHz was the only selected variable explaining the hearing handicap in males and hearing threshold loss at 1kHz and 4kHz, age, and work duration were selected in females. In ROC curves for HHIE-S scores against NIHL as gold standard which was defined by the follow-up audiogram as more than 30dB of the average of 0.5/1/2kHz and 50dB at 4kHz, the optimal cutoff for the parallel HHIE-S appeared to be 8. The results suggest that HHIE-S appeared to have some reliability and validity in this data and might be used in screening NIHL in parallel with pure-tone audiometer in noise-exposed workers.

Selection of Testing Frequency in Bone Vibrator of Audiometer for Measurement of Vivration Perception Threshold / 대한산업의학회지

Both to determine testing frequency in bone vibrator of audiometer for measurement of vibration perception threshold(VPT) and to evaluate factors influencing VPT, ninty seven healthy adults were tested on their second metacarpal head of both hands, at 250Hz, 500Hz, 1,000Hz and so on. Measures of the VPTs at 1,000Hz were excluded in analysis because frequency 1,000Hz was not recognized as a vibration sense. Mean and standard deviation(S.D.) of the VPTs in the both hands measured at 250Hz were 19.9+/-6.7dB, 21.0+/-7.3dB, respectively and at 500Hz were 33.6+/-8.3dB, 34.9+/-8.1dB, respectively. Both mean and S.D. tended to be lower at 250Hz than 500Hz, and mean differences of VPTs between the left and the right hand at the both frequencies appeared statistically significant (p<0.01). VPTs were significantly correlated with each other (p<0.01). Age was positively correlated(p<0.001) with VPTs and education was negatively(p<0.01). Multiple regression analysis showed that age was the only factor influenced on VPT. These results suggest that, when using the bone vibrator of audiometer for measurement of VPT, the frequency 250Hz as a testing frequency may be more useful than frequency 500Hz, and VPT should be measured on both hands.