Biomedical subjects

Kevin J Munro

Publications and source records attributed to Kevin J Munro.

11 recordsLinked to original sources

PubMed2006

Preliminary evidence of asymmetry in uncomfortable loudness levels after unilateral hearing aid experience: evidence of functional plasticity in the adult auditory system.

The aim of the study was to compare uncomfortable loudness levels (ULLs) in a group of adults before and after unilateral hearing aid experience. Twelve participants presented with a symmetrical hearing loss consistent with natural ageing. Pure tones were presented to each ear separately, commencing at 60 dB HL and increased in 5-dB step sizes until ULL was reached. The post-fitting ULLs were typically measured three years after fitting. Hearing thresholds were symmetrical and remained unchanged after fitting. Mean ULL values were symmetrical before fitting. The mean ULL values increased (i.e. greater tolerance) in both ears after fitting; however, the increase was greatest in the fitted ear: 14.5 and 7 dB at 2000-4000 Hz in the fitted and not-fitted ear, respectively. A separate two-factor repeated ANOVA (ear and frequency) was performed on the pre and post-fitting ULL data. There was no statistically significant difference for ear (p > 0.05) when comparing the pre-fitting ULLs. However, there was a statistically significant difference for ear (p < 0.01) when comparing post-fitting ULLs. The underlying mechanism for the asymmetry is unknown but it is consistent with learning induced reorganization within the auditory system.

Acoustic Stimulation↗

PubMed2006

The influence of RECD transducer when deriving real-ear sound pressure level.

OBJECTIVE: The main aim of the present study was to compare the derived and directly measured real-ear hearing instrument performance for a range of commonly used hearing instruments. A secondary aim was to compare the real-ear to coupler difference (RECD) measured using the ER-3A insert earphone and a selection of hearing instruments. DESIGN: The real-ear SPL was measured for four models of hearing instrument in 20 adult participants using an Audioscan RM500 real-ear system. This was compared with the derived real-ear SPL obtained by adding the RECD (measured using the ER-3A insert earphone) to the 2-cc coupler response of each hearing instrument. Measurements were made at 1/12 octave intervals from 0.2 to 6 kHz, using both the HA1 and HA2 2-cc coupler. In addition, the RECD was measured using four models of hearing instrument for comparison with the ER-3A insert earphone values. RESULTS: The procedures were very reliable with mean differences on retest of less than 1 dB. Repeated-measures analysis of variance revealed statistically significant differences between the measured and derived real-ear SPL (p < 0.001) for several models of hearing instrument. The derived responses using the HA1 coupler yielded good accuracy, whereas the HA2 yielded less accuracy. For three models of hearing instrument, the maximum difference was between 5 and 10 dB when using the HA2 coupler. The mean RECD measured with the ER-3A insert earphone and HA2 coupler was not always equivalent to the RECD measured with the hearing instruments. CONCLUSIONS: The accuracy of the derived real-ear response obtained using an RECD, measured with an ER-3A insert earphone, is very good when an HA1 is used for the coupler component of the RECD. The accuracy diminishes somewhat with the HA2 coupler, especially for undamped hearing instruments. The accuracy of the derived real-ear response is very good when the RECD is measured using the hearing instrument and the HA1 or the HA2 coupler.

Adult↗

PubMed2005

Sound quality judgements of new hearing instrument users over a 24-week post-fitting period.

The time course of changes in perceived sound quality after hearing instrument fitting has not been studied systematically It is possible, for example, that patients may object to additional high frequency gain when fitted, but not after a period of auditory acclimatisation. The aim of this study was to utilise sound quality judgements to compare two frequency responses in new users at 4-week intervals over a 24-week post-fitting period. The null hypothesis was that there would be no change in sound quality judgements over time. A total of 16 elderly subjects were fitted monaurally with the same model of linear, programmable hearing instrument. This was set to a standard response that provided 26-29 dB of real-ear insertion gain at 2000 4000 Hz. This program was worn by the subjects for the duration of the study. All subjects reported greater than four hours of daily use. The alternative response which was used in a paired comparison paradigm, provided a mean gain reduction of 3, 8, 13, and 16 dB at 2000, 3000, 4000 and 6000 Hz, respectively. Subjects compared the standard and the alternative responses for sound quality along dimensions of comfort, clarity, and overall preference while listening to running speech presented in quiet, steady noise, and speech babble. At the time of fitting there was a small preference for the standard response when judging clarity, but the alternative response was preferred for comfort and preferred overall. Repeated-measures analysis of variance (ANOVA) for each quality dimension did not reveal any statistically significant change over time. It is concluded that this pattern of preference is unaffected by acclimatisation to amplification, at least over the initial 24 weeks of instrument use.

Acoustics↗

PubMed2005

Reassessment of cochlear dead regions in hearing-impaired teenagers with severe-to-profound hearing loss.

The aim of this study was to reassess cochlear dead regions after an interval of twelve months, using the Threshold Equalising Noise (TEN) test. Thirty-four ears of 24 teenagers (mean age of 14 years) with longstanding severe-to-profound sensorineural hearing impairment were tested. Testing was repeated after an interval of 12 months using the same experimental set-up. A total of eight (23.5%) out of 34 ears changed category on retest: this decreased to two (7.1%) out of 27 ears when the inconclusive category was removed from the analysis. In both of these ears (of the same participant) the criteria were met at a single frequency, and the masked threshold was only 10 dB above the TEN level per ERBN. When all of the data were examined on a frequency-by-frequency basis, the instances that changed category ranged from 15 to 51%. The range decreased to between 4 and 34% when the inconclusive category was removed from the analysis.

Adolescent↗

PubMed2005

The influence of visual feedback on closed-set word test performance over time.

Closed-set word tests can be implemented with or without trial-by-trial visual feedback. Feedback is considered to increase subject motivation yet its influence on performance is unknown. The aim of this study was to compare performance on the Four Alternative Auditory Feature (FAAF) test with and without visual feedback over a 24-week period following fitting of a hearing aid. A total of 32 elderly subjects were recruited as new users and fitted monaurally with the same model of linear, programmable hearing aid that provided in excess of 20 dB insertion gain at 2-4 kHz. Half of the subjects were provided with visual feedback. In these subjects, mean performance increased by 5% across the study period. The improvement in performance over time was statistically significant on analysis of variance (p < 0.05). Mean performance did not increase in the remaining subjects who were not provided with feedback. If closed-set word tests are to be used with visual feedback to measure changes over time, the potentially confounding effects of practice must be controlled carefully. Alternatively, omitting feedback leads to simpler experimental designs.

Aged↗

PubMed2005

Measuring the real-ear to coupler difference transfer function with an insert earphone and a hearing instrument: are they the same?

OBJECTIVE: The purpose of the study was to compare the real-ear to coupler difference (RECD) measured with an insert earphone and two models of hearing instrument. DESIGN: The RECD was obtained from one ear of 18 normal-hearing subjects by subtracting the 2-cc coupler (HA1 and HA2) response from a real-ear aided response, using a conventional probe-tube microphone system. The measurements were made with a conventional ER-3A earphone and two models of behind-the-ear hearing instrument (Unitron US80, Unitron, Kitchener, Canada; and Widex Diva, Widex, Vaerloese, Denmark). RESULTS: The procedures were very reliable, with mean differences on retest of less than 1 dB. There were statistically significant differences between the mean RECDs obtained using an insert earphone compared with those obtained with each hearing instrument (p < 0.05). The differences were greatest when using the HA2 2-cc coupler. For example, the maximum difference in mean RECD between the insert earphone and the Widex Diva was 6 dB and 11 dB when using the HA1 and the HA2 2-cc coupler, respectively. CONCLUSIONS: The RECD is dependent on the acoustic impedance of the sound source, the coupling system, and the coupler and ear. The acoustic impedance may be different for an insert earphone and a given hearing instrument. Therefore, the RECD measured with an insert earphone may not always accurately represent the difference in performance of a hearing instrument measured in the real ear and the 2-cc coupler.

Acoustic Impedance Tests↗

PubMed2005

Comparison of real-ear to coupler difference values in the right and left ear of adults using three earmold configurations.

OBJECTIVE: The purpose of the study was to compare real-ear to coupler difference (RECD) values in the right and left ear of adults using three earmold configurations. DESIGN: The RECD was obtained from both ears of 18 normal hearing adults by subtracting the HA2 2-cc coupler response from the real-ear response using an ER-3A insert earphone and a swept pure tone on the Audioscan RM500 probe-tube microphone system. The measurements were made with a personal earmold, foam eartip, and oto-admittance tip. RESULTS: The mean difference between the right and left RECD was close to 0 dB for all earmold configurations and was not statistically significant on a repeated-measures analysis of variance (p > 0.05). In 90% of participants, the difference between ears was generally less than 3 dB at 0.5 to 4 kHz. CONCLUSIONS: Cooperative participants with non-occluding wax and normal middle ear function (on tympanometry) show small differences in RECD between the right and left ear, irrespective of the earmold configuration. The study has yet to be extended to the clinical setting where subject cooperation and earmold fit may differ from the present study. In the meantime, the findings from the present study indicate that where an RECD can be obtained from only one ear of a participant, it is probably best to use this to derive real-ear SPL of both ears instead of relying on average age appropriate corrections.

Adult↗

PubMed2003

The effect of speech presentation level on measurement of auditory acclimatization to amplified speech.

A systematic improvement in auditory performance over time, following a change in the acoustic information available to the listener (that cannot be attributed to task, procedural or training effects) is known as auditory acclimatization. However, there is conflicting evidence concerning the existence of auditory acclimatization; some studies show an improvement in performance over time while other studies show no change. In an attempt to resolve this conflict, speech recognition abilities of 16 subjects with bilateral sensorineural hearing impairments were measured over a 12-week period following provision of a monaural hearing instrument for the first time. The not-fitted ear was used as the control. Three presentation levels were used representing quiet, normal, and raised speech. The results confirm the presence of acclimatization. In addition, the results show that acclimatization is evident at the higher presentation levels but not at the lowest.

Aged↗

PubMed2003

Application of the TEN test to hearing-impaired teenagers with severe-to-profound hearing loss.

Hearing impairment is often associated with damage to the hair cells of the cochlea. An area of the cochlea with complete loss of function of inner hair cells is known as a 'dead region'. Dead regions can be identified by measuring detection thresholds for pure tones in quiet and in threshold-equalizing noise (TEN). So far, the TEN test has only been used to identify dead regions in adults with moderate-to-severe hearing impairment. The aim of this study was to assess problems in applying the TEN test to teenagers with longstanding severe-to-profound sensorineural hearing impairment, and to assess the prevalence of dead regions in this population. The subjects had a mean age of 14 years, and there were 13 females and 20 males. The stimuli for the TEN test were derived from a CD, whose output was routed via a GSI-16 audiometer and an amplifier to Sennheiser HD580 earphones. For each ear of each subject, both absolute thresholds and masked thresholds in the TEN were measured. For the majority of ears, the results were in-conclusive at some frequencies, due to the maximum output of the audiometer being reached when measuring the absolute or masked threshold. In almost all cases, the diagnosis was uncertain at some frequencies because the TEN could not be made sufficiently intense to produce significant masking. However, for 23 (70%) subjects, the criteria for a dead region at medium or high frequencies were met in at least one ear. For eight (35%) of these subjects, the criteria were only just met. Sixteen of the 24 subjects with a congenital hearing impairment, and four of the five subjects with an acquired impairment, met the criteria for a dead region. The results suggest that dead regions are relatively common among teenagers with a longstanding hearing impairment.

Adolescent↗

PubMed2002

Is the real-ear to coupler difference independent of the measurement earphone?

Direct measurement of real-ear hearing aid performance can be obtained using a probe tube microphone system. Alternatively, it can be derived by adding the real-ear to coupler difference (RECD) to the electroacoustic performance of the hearing instrument measured in a 2-cc coupler. Inherent in this derivation is the assumption that the RECD measured with one transducer can be applied to a coupler measurement performed with a different transducer. For the RECD procedure to be valid, it should be independent of the measurement transducer. The Audioscan RM500 is an example of a commercially available real-ear measurement system that incorporates a clinical protocol for the measurement of the RECD. The RECD can be measured on the Audioscan RM500 using a standard EAR-Tone ER-3A insert earphone or the Audioscan's own RE770 insert earphone. The aim of this study was to compare the RECDs obtained with these two earphones. The Audioscan RM500 was used to measure the RECD from the right ears of 18 adult subjects ranging in age from 22 to 36 years (mean 25 years). Measurements were made with the EAR-Tone ER-3A and RE770 insert earphone and three earmould configurations: (1) the EARLINK foam ear-tip; (2) a hard acrylic shell earmould with the same length of acoustical tubing as the foam ear-tip (25 mm); and (3) the shell ear mould with the appropriate length of tubing for a behind-the-ear (BTE) hearing aid fitting (approximately 35-45 mm). The results show that the mean RECD was around 3 dB higher at 1.5 kHz with the foam ear-tip when measured with the RE770 earphone than when measured with the ER-3A earphone. The same magnitude of difference was obtained with the shell earmould and 25-mm tubing; however, this increased to 9 dB when the tubing was increased to around 40 mm for a BTE fitting. The difference in mean RECD with the two earphones was statistically significant on a repeated-measures ANOVA for every earmould configuration (p<0.001). The results of this study demonstrate that the RECD procedure that uses an HA2 coupler and earmould is not independent of the measurement earphone. This has important implications for clinical practice.

Adult↗

PubMedDate not supplied

Self-reported outcome in new hearing aid users over a 24-week post-fitting period.

Evidence for the existence of auditory acclimatization is mixed, and the implications for clinical practice are unclear. The aim of this study was to seek evidence of perceived changes in performance over a 24-week post-fitting period. Thirty-two new, elderly subjects were recruited and fitted monaurally with the same model of linear, programmable hearing aid that provided in excess of 20-dB insertion gain at 2000-4000 Hz. The Glasgow Hearing Aid Benefit Profile (GHABP) was used to measure self-reported changes over time. The questions concerning benefit and satisfaction were modified to produce two versions: half of the subjects reported changes relative to the time of fitting, while the remainder reported changes relative to the previous occasion on which they completed the GHABP (3 weeks earlier). Subjects reported using hearing aids in excess of 90% of the time when in listening situations that cause difficulty. The median residual disability measure from the GHABP remained low (10-20%) over the duration of the study. The median scores for additional benefit and satisfaction showed a small but statistically significant improvement over the first 3 months of hearing aid use but only for the subjects who referenced this to their perceived performance 3 weeks earlier. The limited evidence for self-reported improvements in benefit and satisfaction over time reported to date must be tempered by the possibility of response bias arising from the method used to measure changes over time.

Adaptation, Physiological↗