Biomedical subjects

J R Franks

Publications and source records attributed to J R Franks.

8 recordsLinked to original sources

PubMed1992

Real ear attenuation at threshold for three audiometric headphone devices: implications for maximum permissible ambient noise level standards.

Attenuation measurements were made using the ANSI S12.6-1984 protocol on a standard Telephonics headset with TDH-50P earphones and Model 51 cushions, Amplivox Audiocups headphone enclosures, and Peltor AudioMate headphone enclosures. Each of the enclosures housed Telephonics TDH-50P earphones with Model 51 cushions. The mean attenuation values obtained were compared with those previously reported, and reasons for discrepancies were analyzed. Pure-tone threshold shifts in background noise complying with ANSI S3.1-1977 and Occupational Safety and Health Administration (1983) maximum permissible ambient noise level standards were estimated on the basis of the attenuation values for each headphone device, and the adequacy of these current standards for accurate pure-tone threshold assessment was considered. The results indicated that Model 51 cushions alone are insufficient to attenuate the ambient noise levels permitted under ANSI S3.1-1977, and even the utilization of noise-excluding headphone enclosures does not reduce the background noise levels permitted under the Occupational Safety and Health Administration (1983) to a sufficient degree to permit testing down to 0 dB HL.

Adult↗

PubMed1992

The effect of fitting procedure on hearing protector attenuation.

Realistically evaluating the effectiveness of hearing protectors continues to be a major problem in hearing conservation. The purpose of this study was to examine a laboratory-based fitting procedure (User Fit) that was designed to yield hearing protector attenuation values similar to that derived from field studies. Ten subjects who were naive to hearing protectors were used in a repeated measures design that measured real ear attenuation at threshold for two types of plugs. Each subject was tested in two fitting conditions that varied based on the type and degree of assistance given to the subjects by the experimenter. The results showed significant differences in attenuation based on the fitting procedure used, with the User Fit best approximating field data. In addition, a generalized learning effect was noted. The results suggest that any experience with earplugs leads to subsequent improvement in attenuation despite the type of earplug used. Further testing is planned with greater numbers of subjects and additional types of hearing protectors.

Adult↗

PubMed1991

Hearing loss in the chinchilla from impact and continuous noise exposure.

The relative hazard posed to the peripheral auditory system by impact/impulse and continuous noise of the same power spectrum was determined. Impact noise was generated by striking a nail with a hammer and was digitally recorded. The acoustical power spectrum of the impact was determined and pink noise was filtered to produce a continuous noise stimulus with the same acoustic power spectrum. Pre-exposure auditory evoked response (AER) thresholds were obtained at 1, 2, 4, and 8 kHz on 16 adult chinchillas. The pool of animals was divided into two equal groups based upon pre-exposure AER thresholds. One group was exposed to impact noise and the other group to the filtered pink noise. Exposures were 4 h/day for 5 days. Thirty days following the exposure, auditory evoked response thresholds were remeasured. Changes in auditory sensitivity were determined by subtracting the pre-exposure thresholds from the post-exposure thresholds. Hearing threshold shifts of the impact noise group were significantly greater (p less than 0.0001) than the hearing threshold shifts of the continuous noise group. These data indicate a need to more closely examine the parameters and effects of impact noise. There may be a need to develop expanded damage-risk criteria for occupational exposure to impulse/impact noise.

Animals↗

PubMed1990

Real-ear attenuation of earmuffs in normal-hearing and hearing-impaired individuals.

Many of the 9 million workers exposed to average noise levels of 85 dB (A) and above are required to wear hearing protection devices, and many of these workers have already developed noise-induced hearing impairments. There is some evidence in the literature that hearing-impaired users may not receive as much attenuation from hearing protectors as normal-hearing users. This study assessed real-ear attenuation at threshold for ten normal-hearing and ten hearing-impaired subjects using a set of David Clark 10A earmuffs. Testing procedures followed the specifications of ANSI S12.6-1984. The results showed that the hearing-impaired subjects received slightly more attenuation than the normal-hearing subjects at all frequencies, but these differences were not statistically significant. These results provide additional support to the finding that hearing protection devices are capable of providing as much attenuation to hearing-impaired users as they do to normal-hearing individuals.

Audiometry, Pure-Tone↗

PubMed1989

Analysis of a hearing conservation program data base: factors other than workplace noise.

The hearing conservation records of a large, multiple-facility printing company were obtained. The records were analyzed for factors associated with Standard Threshold Shift. These factors included hearing levels, employee age and sex, occupational and nonoccupational noise exposure histories, and medical history. The analysis revealed that statistically significant factors associated with Standard Threshold Shift were from medical and nonoccupational noise exposure histories, and not occupational noise exposure.

Adult↗

PubMedDate not supplied

Variable venting valve for earmolds.

The frequency response and loudness reduction characteristics of earmolds with variable venting valves (VVV) were investigated. Both side-branch and laterally vented earmolds were employed. Sound pressures were measured at 44 frequencies from 100 to 4 000 HZ in a modified HA-2 coupler with the VVV in four stages of opening: closed; 1/3 open; 2/3 open and 3/3 open. The effect of venting is primarily in the low frequencies. Little or no reduction in intensity is observed in the 'speech frequency' range and a modest amount is noted in the higher frequencies. The side-branch vented earmolds were more effective than the laterally vented earmolds. Calculated loudness reductions in phons were small. The effectiveness of the VVV, whether assessed by the frequency response or loudness reduction characteristics, is achieved within the first 1/3 of opening: further opening has little effect. The utility of the VVV, especially to the geriatric hearing aid user, is questionable.

Hearing Aids↗

PubMedDate not supplied

The effect of spatial separation of speech and noise sources on the optimal setting of the master hearing aid.

The sound fields in which hearing aid evaluations are performed with tests of speech discrimination are far from standardized. This investigation was concerned with the nature of the sound field in terms of separation of speech and noise sources as related to the optimal setting of a master hearing aid as indicated by listener performance scores on tests of speech discrimination in noise. Two sound fields were used in this investigation, one with speech and noise from the same source and another with speech and noise sources separated by 90 degrees and 45 degrees off the axis of the midsagittal plane of the listener. The repeatability of the optimal setting of the master hearing aid from one configuration to the other and the resolution available in each sound field, were of prime interest. The data indicated that the sound field configuration has no bearing on the optimal setting of the master hearing aid. The data did indicate that maximum resolution was available in the case of speech and noise from the same source.

Acoustic Stimulation↗

PubMedDate not supplied

Filter effect of earmold venting: comparison of electroacoustic and psychoacoustic methods of evaluation.

The filter effect of venting an earmold was evaluated by measuring the coupler-acoustic and threshold responses to open versus closed earmolds. In the coupler-acoustic technique the effect of venting was determined by measuring the output of the experimental earmolds seated on a modified 2-cc coupler with a specified signal impressed upon the earphone. The real ear threshold technique called for the determination of threshold by five listeners for the same earphone-earmold system. The data indicated that the difference between the coupler and threshold measures were of the same order of magnitude as the difference seen by other investigators reporting coupler and real ear-probe tube microphone measures. It was concluded that the threshold technique provides the same general description of the effects of venting an earmold as does the probe tube technique and should thus provide a useful method for determination of the filter effects produced by the venting of an earmold.

Auditory Threshold↗