Biomedical subjects

J J Dempsey

Publications and source records attributed to J J Dempsey.

16 recordsLinked to original sources

PubMed1992

Computer-assisted tracking simulation (CATS).

The tracking technique involves a sender reading consecutive segments from a story and a receiver attempting to repeat each segment verbatim. The reliability and validity of the tracking procedure have been criticized based upon uncontrolled variables such as sender, receiver, and text characteristics. To address these problems, a computer-assisted interactive tracking simulation (CATS) system has been developed in which story segments are presented to the receiver via a video laser disc system and repair strategies are implemented through a computer program.

Communication Devices for People with Disabilities↗

PubMed1991

An evaluation of two signal-processing hearing aids.

Various forms of signal processing are used in modern ASP hearing aids. The present study investigated the relationship between sentence recognition ability and two types of signal processing used in commercially available hearing aids. Results indicated a significant improvement in sentence recognition ability employing an instrument with adaptive compression (variable release time) versus an instrument with an adaptive high-pass filter with short attack and release times. Data were obtained for a single-talker competing message at several message-to-competition ratios. The adaptive compression system may prove to be beneficial to hearing-impaired listeners in certain background noise environments.

Aged↗

PubMed1990

Bone vibrator placement and the cancellation technique.

An issue in the measurement of bone conduction sensitivity is the placement of the bone vibrator. The effect of bone vibrator position on the amplitude and phase of the received signal was investigated using a cancellation technique. This technique involves cancelling the signal delivered by the bone vibrator with a signal delivered acoustically via an earphone. At cancellation, the acoustic signal is equal in amplitude but opposite in phase to the bone-conducted signal. Results showed that the amplitude of the received signal did not vary significantly with bone vibrator position close to the center of the forehead whereas the phase of the received signal was critically dependent on bone vibrator position. Substantial intersubject differences were observed in the variation of phase with bone vibrator position. The precision of measurement using the cancellation technique was found to be high.

Acoustics↗

PubMed1990

The occlusion effect created by custom canal hearing aids.

There has recently been a dramatic increase in the demand for custom canal hearing aids. One of the significant limitations sometimes created by these instruments is the increased sensitivity to bone-conducted stimuli known as the occlusion effect. A large occlusion effect is often cited as the reason for rejection of these devices. This investigation tested a method of measuring the occlusion effect through bone-conducted speech reception thresholds (SRTs). The results indicated that the bone conducted SRT procedure is sensitive enough to differentiate between the occlusion effect created by shell earmolds versus canal hearing aids.

Bone Conduction↗

PubMed1986

Relationship between head size and latency of the auditory brainstem response.

This investigation examines the relationship between the head size of 22 normally hearing individuals and the latency of their respective auditory brainstem responses (ABR). The absolute latency of wave V and the I-V interpeak interval were examined in 12 female and 10 male subjects with varying head sizes. Strong positive correlations were obtained between head size and the latency of both wave V and the I-V interpeak interval. The evidence suggests that this relationship is based upon subject differences in brain size which is reflected in head size. Head size appears to be an important source of intersubject variability which should be considered in order to increase the clinical usefulness of the ABR.

Adult↗

PubMed1985

A functional measure of front-to-back ratio.

Monaural hearing aid users (aged 26-75 yrs; mn: 52 yrs) with moderate to severe bilateral sensorineural losses tracked free field sweep-frequency Bekesy thresholds from .25-4 kc/s in a typical audiological test booth. Each S was fitted, on the ear on which S usually wore an aid, with successively 3 directional microphone hearing aids (DMHAs) now commonly issued, with similar frequency response and gain characteristics but with a range, as shown by the manikin KEMAR in an anechoic chamber, of 8 db in FBR. Warbled tones were presented from a loudspeaker either 1 m directly ahead of or 1 m directly behind S's head. The difference in thresholds (180 degrees data subtracted from 0 degree data) in db was taken as functional front-to-back ratio (FBR) at selected frequencies. These were compared with FDRs from KEMAR. The functional FBR was shown to be sensitive enough (p less than .001) to differentiate among DMHAs, and the aids were on the average ordered similarly from highest to lowest by both KEMAR and functional FBRs. It was found that the data at 1 kc/s were predominately useful to test. However, individual differences were such that it was concluded that more reliance should be placed on a functional test of FBR. In addition, a significant Pearson r of 0.42 (p less than .01) was obtained between functional FBR and monosyllabic DS (S/N: 0 db). These results suggest that the functional FBR may play an important role in measuring hearing aid selection.

Adult↗

PubMed1974