Biomedical subjects

V D Larson

Publications and source records attributed to V D Larson.

6 recordsLinked to original sources

PubMed1992

Occluded-ear simulator with variable acoustic properties.

Ear simulators were designed to replicate acoustical characteristics of the average adult ear. Due to variability of ear-canal geometry and eardrum impedance among individuals, the possibility of any one person exhibiting such "average" characteristics--especially if that person is a child and/or has a conductive pathology--is remote. Thus, ear simulators have been of only peripheral value when prescribing a hearing aid (a high output impedance device) to fit the acoustical requirements of a particular patient. Reported herein is development of a programmable artificial ear (PAE) that can account for individual differences in ear-canal geometry and eardrum impedance. It consists of a 2.0-cc coupler, microphone, amplifier, computer, PAE code, and a computer card and/or software for digitization and Fourier transformation. Required input data includes ear-canal dimensions, eardrum impedance, and output impedance of the hearing aid being tested. Sound-pressure recordings produced in the 2.0-cc coupler by the hearing aid are adjusted by the computer to what they would have been had the recordings been made at the eardrum of a particular patient wearing the same hearing aid. Good agreement was observed between experiment and theory for one test case involving a totally occluding miniature earphone.

Acoustic Impedance Tests↗

PubMed1989

A comparison of three HA-1 couplers.

The use of 2-cm3 couplers for measuring the output of an ER-3A earphone has been recommended. The purpose of this study was to compare the acoustic output of three commonly available couplers and to study the intra- and inter-examiner reliability with which those measurements may be performed. While the repeatability of measurements, at least for clinical purposes, was good even for hand-held coupling of the earphone to the couplers, differences between couplers were observed. These differences were influenced by the positioning of the sound-outlet orifice relative to the interior, top wall of the couplers' cavities. A recommendation for 2-cm3 coupler calibration of the ER-3A earphone using a commonly available adapter was made.

Acoustics↗

PubMed1989

Simulated hearing loss and phrase dictation.

The effect of simulated high frequency hearing loss in young adult speakers was examined. Subjects were native English speakers with normal hearing sensitivity. There were three listening conditions, two filtered conditions simulating high frequency hearing losses similar to those often occurring in the geriatric population and one unfiltered, or normal condition. Subjects listened to the Phrase Repetition subtest of the Boston Diagnostic Aphasia Examination. There were significant differences in the number of errors across the three conditions, with the most errors occurring during the greater simulated hearing loss. Such errors may be attributed to expressive language impairments when errors may instead be the result of a high frequency hearing loss.

Adult↗

PubMed1977

A comparison of three hearing aid evaluation procedures for young children.

The evaluation of hearing aid performance with young, nonverbal children traditionally consists of a comparison between aided and unaided thresholds. Alternative evaluation procedures include those that provide an estimate of the speech spectrum area that is potentially audible to the child with amplification. This study compared the hearing aid performance results for ten hearing impaired children evaluated with a sound field procedure and two speech spectrum methods. Results obtained for three hearing aids demonstrated no differences in hearing aid recommendation between procedures for children with only mild-moderate hearing loss. For children with severe to profound losses, however, the sound-field audiogram was found to overestimate what is potentially audible to the child.

Child↗

PubMed1977

Split-half reliability of two word discrimination tests as a function of primary-to-secondary ratio.

Two clinical word discrimination tests, the Northwestern University Auditory Test No. 6 (NU-6) and the Modified Rhyme Test (MRT), were examined for internal consistency and for split-half reliability under varying primary-to-secondary ratios (P:S) in normal hearers. Although the statistical analysis indicated that half-lists could be used reliably for both discrimination tests at most P:S conditions, the wide variability found among individual listeners does not support the clinical practice of half-list testing in noise--at least not for normal-hearing listeners.

Adult↗

PubMedDate not supplied

Sound levels in a 2-cc cavity, a Zwislocki coupler, and occluded ear canals.

Probe-tube measurements of the differences in sound levels at three locations in ear canals were compared to the differences in levels measured at analogous positions in a Zwislocki coupler and a 2-cc cavity. The results support the recommendation of Sachs and Burkhard that probe tube measurements should not be made with the probe tube flush with the earmold tip and close to the sound inlet bore. In real ear canals the transfer functions to the eardrum presented by Bruel, Frederikson, and Rasmussen and by Studebaker agree well with each other but differ somewhat from the one used by Sachs and Burkhard. In agreement with Bruel et al., the data of this study reveal a plateau in the relationship between real ear and 2-cc cavity responses between about 1.6 and 4.0 kHz, the relative intensity level of which may depend upon residual ear canal volume.

Acoustics↗