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Biomedical subjects

T Frank

Publications and source records attributed to T Frank.

104 records · Page 6Linked to original sources
PubMedDate not supplied

Acoustic radiation from bone vibrators.

Our purpose was to investigate the influence of acoustic radiation produced by bone vibrators at 4000 Hz on bone conduction (BC) testing. In one study, BC thresholds were obtained with a Radioear B-70A, B-71, and B-72 vibrator when the subject's ear canal was unoccluded and occluded. In another study, probe-tube microphone measurements were made just inside the entrance to the ear canal for each vibrator and for an air conduction source at comparable sensation levels. Results of both studies were interpreted to indicate that the B-70A and B-71 produced minimal acoustic radiation. However, the B-72 was found to have excessive acoustic radiation which would be sufficient to influence BC thresholds and produce an invalid high-frequency air-bone gap.

Acoustics↗
PubMedDate not supplied

Frequency response and output variations of Radioear B-71 and B-72 bone vibrators.

Frequency response curves were obtained for a Radioear B-71 and a B-72 bone vibrator with a revised Bruel and Kjaer model 4930 artificial mastoid. The curves for each vibrator were characterized by three resonant peaks which decreased in amplitude as frequency increased. The maximal output voltage variations of the artificial mastoid were less than or equal to 2 dB for each vibrator at all audiometric frequencies (+/- 3%), except for the B-72 at 4000 Hz where the variation was 6.9 dB. Overall, the findings were interpreted to question the use of a +/- 3% frequency tolerance for the generation and calibration of reference bone conduction thresholds.

Acoustics↗
PubMedDate not supplied

Influence of contralateral masking on bone-conduction thresholds.

Two studies were conducted using normal-hearing listeners. In study 1, bone-conduction (BC) thresholds were obtained with contralateral masking at an effective level (EL) of 30 and 35 dB. In study 2, the EL of the contralateral masking equaled the magnitude of the occlusion effect (OE) plus a safety factor of 10 and 20 dB. Within each study, BC threshold shifts were evident at the higher compared with the lower ELs. Between studies, the highest BC thresholds were always obtained in the presence of the highest SPL of the masker which occurred in the 35 dB EL condition, whereas the lowest BC thresholds were always obtained in the presence of the lowest SPL of the masker which occurred in the OE + 10 dB condition. Even though the BC thresholds were influenced by the amount of contralateral masking, the BC thresholds obtained in each study were in good agreement with the new ANSI S3.26-1981 BC reference thresholds.

Adult↗
PubMedDate not supplied

Telephone listening ability in a noisy background.

Telephone handsets have a built-in side-tone feedback because the transmitter feeds back sound through the receiver, allowing users to monitor their voice levels. However, the side-tone feedback system also picks up background noise which interferes with the incoming speech signal. This study investigated the influence of side-tone feedback on the telephone listening ability of 30 normal-hearing subjects in a background of multitalker (MT) and white noise (WN) presented at 65, 75, and 85 dB SPL in two conditions where the side-tone feedback was present and in three conditions where the side-tone was eliminated. Telephone listening ability significantly decreased as the level of the noise increased for both MT and WN and for all listening conditions. Telephone listening ability was significantly poorer in the background of MT than WN for each noise level and listening condition. The primary finding was that telephone listening ability in a background of MT or WN at the higher levels was significantly improved when the side-tone feedback was eliminated by electronically disengaging or more simply by occluding the transmitter with the palm of the hand.

Adult↗
PubMedDate not supplied

Telephone listening ability for hearing-impaired individuals.

Forty-five subjects with bilateral sensorineural hearing losses were divided into three groups (N = 15/group) based on the audiometric configuration of their test ear. The subjects were evaluated in three listening conditions by assessing their word discrimination ability by presenting stimuli at 86 dB SPL (simulating the output of a standard telephone handset ) and most comfortable loudness (MCL) (simulating the output of a telephone amplifier handset ). The three listening conditions were TDH-39 earphone, unaided telephone, and aided telephone with their personal hearing aid acoustically coupled to a telephone handset . Results indicated that subjects with precipitous hearing losses had similar word discrimination scores for all three listening conditions at 86 dB SPL and MCL. Subjects with gradual slope or flat hearing losses had similar word discrimination scores with a TDH-39 earphone, unaided telephone, and their hearing aids acoustically coupled to a telephone handset at 86 dB SPL. The subjects with gradual slope or flat losses also had similar word discrimination scores across the listening modes at MCL, but they had better word discrimination scores in all listening modes when the word lists were presented at MCL compared with 86 dB SPL.

Hearing Aids↗
PubMedDate not supplied

Influence of temperature on the output of a mechanical coupler.

This research determined the influence of temperature on the output of two Bruel and Kjaer 4930 mechanical couplers using a Radioear B-71, B-72, and a Pracitronic KH 70 bone vibrator. When the temperature of the mechanical couplers was varied from 17 degrees C (62.6 degrees F) to 29 degrees C (84.2 degrees F) in steps of 3 degrees C (5.4 degrees F) and the bone vibrators had a constant temperature, the output of each mechanical coupler systematically decreased as its temperature increased for each bone vibrator type. The largest output differences for both couplers and each vibrator occurred at 4000 Hz. The average of these differences across the couplers and vibrators was 6.6 dB higher at 17 degrees C than at 29 degrees C which dB/3.6 degrees F). When the temperature of the bone vibrators was 17 and 29 degrees C and the mechanical couplers were maintained at a constant temperature, there were little or no differences in the output of the mechanical couplers. The temperature of a mechanical coupler rather than that of the bone vibrator is a critical variable in bone conduction calibration. Mechanical coupler temperature-dependent output coefficients were determined for use in bone conduction calibration from 250 to 4000 Hz for all three bone vibrator types and at 6000 and 8000 Hz for the KH 70.

Audiometry↗
PubMedDate not supplied

Combined MR imaging and spectroscopy of bone and soft tissue tumors.

Twenty-three patients with bone and soft tissue tumors were studied with combined magnetic resonance (MR) imaging and spectroscopy. The MR examinations were utilized to determine the size, internal characteristics, and relationships of the tumor to the surrounding tissues. They also determined the optimal placement of the surface coil. The surface coil profile was the localization technique utilized. Four patients were also studied with one-dimensional chemical shift localization. Tumors were grouped according to histologic type, degree of muscle contamination, size, and extent of necrosis. Quantitative comparison among the groups was carried out by comparing the mean ratios of the low-energy phosphate portion of the spectra [phosphomonoester (PME), Pi, phosphodiester (PDE)] to beta-nucleotide triphosphate (NTP). Tumor spectra typically showed a relative elevation in PME, Pi, and PDE and a relative decrease in phosphocreatinine. No characteristic spectra were observed for individual tumor types. Contamination of the tumor spectra from surrounding muscle impaired interpretation of the spectral data. Tumor size and extent of necrosis were important determinants of the relative degree of abnormally elevated metabolite peaks (PME, Pi, PDE). A trend toward a higher mean PME/beta-NTP ratio was observed among high-grade lesions. Combined MR imaging and spectroscopy is a useful way to study tumor metabolism. Muscle contamination is a significant problem in analysis of the spectra. Better localization techniques are required.

Bone Neoplasms↗
PubMedDate not supplied

Effect of contralateral noise on speech detection and speech reception thresholds.

Speech detection thresholds (SDT) and speech reception thresholds (SRT) for spondee words were obtained on 20 normal hearing listeners while white or speech noise making was presented to the contralateral ear. Each masker was presented continously or pulsed simultaneously with the onset of each spondee word. Several masker sensation levels (SL) of 30, 40, 50, 60, 70, and 80 dB were employed, and the amount of masking (threshold shift) was determined for each condition. Small but consistent SDT and SRT shifts were apparent at low masker SLs (30 dB). FOR 60-80 DB masker SLs, the shifts were about 3.5 dB for each 10-dB increase in the masker. The greater threshold shifts at the higher masker SLs may have resulted from transcranial conduction and/or activation of the acoustic reflex. The pulsed masker condition had more of an effected on the SDT than on the SRT; SDT shifts were consistently larger for each masker SL when the masker was pulsed compared to continuous presentation. Overall, the average threshold shifts ranged from about 1 to 11 dB as the masker SL was increased from 30 to 80 dB. These data suggest that central masking is operating for masker SLs below 60 dB; for higher masker SLs, the increased threshold shifts probably result from a combination of central masking, transcranial conduction, and acoustic stapedius reflex action. The clinical implications of central masking are also discussed.

Adult↗