Influence of bone conduction transducer type and placement on ocular and cervical vestibular evoked myogenic potentials

Evaluating the effectiveness of different bone conduction (BC) transducers with controlled coupling force to elicit cervical and ocular vestibular evoked myogenic potentials (cVEMPs, oVEMPs) in healthy subjects by comparing response rates, amplitudes, latencies, thresholds and asymmetry ratios. Prospective experimental study including healthy participants. VEMPs were measured to different stimulation modes; the BC transducer coupling force was controlled to 5.4 (± 0.5) Newton. cVEMPs: to bone conducted vibration (BCV) with the B81 transducer on the mastoid; oVEMPs: to BCV with the B81 on the mastoid, BCV with the B81 on the forehead, and BCV with the Mini-Shaker 4810 on the forehead. Air conducted sound (ACS) with insert earphones was used as reference. Data of 24 normal subjects (mean age 25.3 (± 3.0) years) were analyzed. ACS and BCV with the B81on the mastoid evoked cVEMPs in 100% of ears. The highest oVEMP response rates were obtained with the B81 on the mastoid (83–92%), the lowest with the B81 on the forehead (17–22%). The Mini-Shaker elicited lower response rates (65%) compared to results from the literature without coupling force control and compared to ACS (78–87%). Amplitudes were higher for BCV than ACS. ACS and BCV on the mastoid caused higher asymmetry compared to BCV forehead stimulation. The B81 was feasible to elicit VEMPs with mastoid placement and can be used as an approved medical device to measure BCV VEMPs in a clinical set-up. Normative asymmetry values have to be established due to higher variability for mastoid stimulation.

Influence of bone conduction transducer type and placement on ocular and cervical vestibular evoked myogenic potentials

Purpose: Evaluating the effectiveness of different bone conduction (BC) transducers with controlled coupling force to elicit cervical and ocular vestibular evoked myogenic potentials (cVEMPs, oVEMPs) in healthy subjects by comparing response rates, amplitudes, latencies, thresholds and asymmetry ratios.Methods: Prospective experimental study including healthy participants. VEMPs were measured to different stimulation modes; the BC transducer coupling force was controlled to 5.4 (±0.5) Newton. cVEMPs: to bone conducted vibration (BCV) with the B81 transducer on the mastoid; oVEMPs: to BCV with the B81 on the mastoid, BCV with the B81 on the forehead, and BCV with the Mini-Shaker 4810 on the forehead. Air conducted sound (ACS) with insert earphones was used as reference.Results: Data of 24 normal subjects (mean age 25.3 (± 3.0) years) were analyzed. ACS and BCV with the B81on the mastoid evoked cVEMPs in 100% of ears. The highest oVEMP response rates were obtained with the B81 on the mastoid (83 – 92%), the lowest with the B81 on the forehead (17 – 22%). The Mini-Shaker elicited lower response rates (65%) compared to results from the literature without coupling force control and compared to ACS (78 – 87%). Amplitudes were higher for BCV than ACS. ACS and BCV on the mastoid caused higher asymmetry compared to BCV forehead stimulation.Conclusion: The B81 was feasible to elicit VEMPs with mastoid placement and can be used as an approved medical device to measure BCV VEMPs in a clinical set-up. Normative asymmetry values have to be established due to higher variability for mastoid stimulation.

Cross-site investigation on head-related and headphone transfer functions: variabilities in relation to loudness balancing

Headphone transfer function (HpTF) and head-related transfer function (HRTF) measurements are crucial in acoustic science and in binaural virtual acoustic applications. Yet, their measurement set-up, procedure or post-processing is different for nearly every lab, especially for the HRTF measurements. To compare findings between different labs, these measurement deviations have to be quantified alongside with their influence on perceptual aspects. In the scope of a cross-site investigation on loudness balancing between headphone and loudspeaker listening, a set of HpTFs with three different headphones (open, closed, insert earphones) and HRTF close to the eardrum were measured in 14 participants travelling to two different measurement sites at Aachen and Oldenburg. Though set-ups for measuring the HRTF are very different between sites, the gathered HRTFs are quite consistent across them. For the measured HpTFs, across sites the open headphones consistently yield a slightly lower variability in the range from 70 to 5000 Hz than the closed one while the insert earphones exhibit much higher variabilities and a limited range of reproducible results. The difference in loudness balancing across labs could well be predicted by site-specific systematic differences in HpTFs with the exception of 1 kHz narrowband stimulus. This clearly indicates the limits in comparability of HpTFs and loudness balancing across labs and the importance of using headphones with high repeatability like the open ones used in this investigation.

Self-reported hearing status and audiometric thresholds among college students using headphones

Purpose: The study aims to investigate headphone listening habits of college-going students and for those using headphones, correlate self-reported hearing status with average audiometric hearing thresholds. Method: Headphone listening habits and awareness of adverse effects of the same was profiled in college-going students using a questionnaire distributed through online platform. Hearing thresholds were then compared for those with and without self-report of hearing difficulty. 341 responses were obtained from students between 17 and 23 years of age. For the second part of the study, a convenience sample of 30 willing students from among these 341 was selected. Pure tone thresholds were obtained for various frequencies with a high frequency audiometer. PTA (average of 500, 1000, 2000 Hz) and HFPTA (average of 4000, 6000, 8000, 10000 Hz) were calculated for both the ears and compared for those with and without reported hearing difficulty. Results: 78% students reported headphone usage for less than 3 hours per day, while 22% reported usage for more than 3 hours per day. 77% respondents were aware that listening to loud sounds can alter hearing sensitivity, but many (54.83%) did not have awareness about the minimum safe hours of listening. There was a weak positive correlation between self-reported hearing difficulty and poor ear HFPTA (r = 0.2304). Conclusion: Majority of students used insert earphones even after knowing the adverse effect of the same. There was a weak correlation found between the self-reported hearing problems and audiometric hearing thresholds. Implication: More awareness is needed about the ill effects of headphone usage amongst the young teenage population. Proper counseling and management strategies are required for people who report difficulty in hearing.

Do Room Acoustics Affect the Amplitude of Sound-Field Auditory Steady-State Responses?

The sound-field auditory steady-state response (ASSR) is a promising measure for the objective validation of hearing-aid fitting in patients who are unable to respond to behavioral testing reliably. To record the sound-field ASSR, the stimulus is reproduced through a loudspeaker placed in front of the patient. However, the reverberation and background noise of the measurement room could reduce the stimulus modulation used for eliciting the ASSR. As the ASSR level is heavily dependent on the stimulus modulation, any reduction due to room acoustics could affect the clinical viability of sound-field ASSR testing. This study investigated the effect of room acoustics on the level and detection rate of sound-field ASSR. The study also analyzed whether early decay time and an auditory-inspired relative modulation power model could be used to predict the changes in the recorded ASSR in rooms. A monaural auralization approach was used to measure sound-field ASSR via insert earphones. ASSR was measured for 15 normal-hearing adult subjects using narrow-band CE-Chirps® centered at the octave bands of 500, 1000, 2000, and 4000 Hz. These stimuli were convolved with simulated impulse responses of three rooms inspired by audiological testing rooms. The results showed a significant reduction of the ASSR level for the room conditions compared with the reference anechoic condition. Despite this reduction, the detection rates for the first harmonics of the ASSR were unaffected when sufficiently long recordings (up to 6 min) were made. Furthermore, the early decay time and relative modulation power appear to be useful predictors of the ASSR level in the measurement rooms.

Effect of Sound Source Location and Spatial Hearing on the Vestibulo-Ocular Reflex (VOR)

Accurate measurement of the vestibulo-ocular reflex (VOR) is imperative in differential diagnosis of vestibular disorders and balance function. However, the assessment protocol faces a number of limitations, including the need to control for extra- vestibular sensory factors such as hearing. Previous research has shown that the use of an auditory stimulus can have a significant effect on functional measures of balance, and many have contributed effects to be the result of spatial hearing. However, no studies have directly assessed the effect of speaker location on the VOR nor investigated correlations of functional spatial hearing with the VOR. Therefore, the aims of this study were to 1) assess the effect of speaker location on the VOR and 2) investigate if spatial hearing abilities are correlated with the strength of the VOR. A between subjects repeated measures design was utilized with a child group (age 6-9 years) and an adult group (18-40 years). The rationale of the two groups was to compare differences in a group with underdeveloped localization abilities (child) and a group with matured localization abilities (adult). A total of 22 children and 23 adults participated in this study. Localization ability was measured using the root mean square (RMS) error method. VOR gain was measured using the rotational chair test at a rate of .08 Hz in the following auditory conditions: silent (insert earphones turned off), insert earphones turned on, external speaker at 0° azimuth rotating with participant, and external stationary speaker. Order of testing was randomized to control for any order effects. An independent samples t-test confirmed a significant difference in RMS error between groups with the child group performing worse than the adults. Subsequent multivariate analysis of variance indicated a significant effect for speaker location with the external moving speaker having significantly lower gain and the external stationary speaker having significantly increased gain for both child and adult groups. Correlations were run for both groups for both fixed and moving speaker conditions. No correlation was seen in either condition for the child group, however, a positive correlation was seen for both conditions for the adult group, meaning as RMS error increased so did VOR gain. These results indicate the possible need to control for environmental auditory stimulus location when undergoing vestibular assessment. However, further studies need to be performed to corroborate the evidence presented.

Effects of Self-Generated Noise on Quiet Threshold by Transducer Type in School-Age Children and Adults

Purpose Low-frequency detection thresholds in quiet vary across transducers. This experiment tested the hypothesis that transducer effects are larger in young children than adults, due to higher levels of self-generated noise in children. Method Listeners were normal-hearing 4.6- to 11.7-year-olds and adults. Warble-tone detection was measured at 125, 250, 500, and 1000 Hz with a sound-field speaker, insert earphones, and supra-aural headphones. Probe microphone recordings measured self-generated noise levels. Results Thresholds were similar across ages for speaker measurements. Transducer effects were larger for children than adults, with mean child–adult threshold differences at 125 Hz of 3.4 dB (insert earphones) and 6.6 dB (supra-aural headphones). Age effects on threshold were broadly consistent with noise levels measured in the ear canal. Conclusions Self-generated noise appears to elevate children's low-frequency thresholds measured with occluding transducers. These effects could be particularly relevant to the diagnosis of minimal and mild hearing loss in children.

Effect of Forward Masking on Frequency Following Response as a Function of Age

Background: Forward masking occurs when noise is presented before the target signal, making thelatter difficult to be perceived. It is related to temporal auditory processing and consequently to speechrecognition in noisy environments, which may decline with age. Interest in forward masking has grown inthe last years. Studies investigate psychoacoustic and electrophysiological recordings in different age groups.<br />Purpose: The purpose of the study was to investigate the effect of forward masking on frequency followingresponse (FFR) as a function of age.<br />Research Design: Cross-sectional analytical observational study.<br />Study Sample: We assessed 69 normal-hearing participants of both genders assigned to three groups: 40young individuals (aged 18–25 years,mean age = 22 years, 8 months), 21 middle-age individuals (aged 25–55years, mean age = 37 years, 2 months), and 8 seniors (aged < 55 years, mean age = 65 years, 3 months).<br />Intervention: FFRs were recorded using the /da/ syllable with and without noise.<br />Data Collection and Analysis: The /da/ syllable and speech-shaped noise were monaurally presentedto the participants’ right ears through ER-3a insert earphones. Electrodes were placed in M1 and M2 (-),Fz (+), and Fpz (ground). Acquisition occurred under two conditions: (1) the /da/ syllable presented withoutthe noise and (2) the /da/ syllable presented 4 msec after the noise.<br />Results: Data show that (1) considering the mean values of all participants, there was a significant latencydelay of all waves (PV, A, PW, PX, PY, PZ, and O) when the /da/ syllable was presented 4 msecafter the masking noise as compared with the condition without noise, that is, forward masking occurredin all components of the FFR responses, and (2) for the youngest group and the middle-age group, forwardmasking was seen for all waves, except PX in the latter one; for the senior group, an irregular patternwas observed (presence of forward masking in PA, PY, PZ, and O). This pattern may be due to an agingeffect on FFR responses even without noise presence, which makes it more difficult to identify forwardmasking effect in this population. Although it is well documented in the literature that forward maskingincreases with age, this is less evident on FFR recordings in the senior population.<br />Conclusions: An aging effect was identified in FFR responses. Forward masking was identified in FFRresponses of all groups but less evident in senior population.<br />

Accounting for the Occlusion Effect with Insert Earphones

There are clinical implications associated with knowing when the occlusion effect (OE) must be accounted for during bone conduction (BC) testing because spurious results can occur when errors are made in this regard. The amount of OE produced when insert earphones (IEs) are used varies in the literature; thus, further investigation is warranted.The purpose of this project was to determine the OE during BC threshold measurements under the following occluding conditions used clinically: when using partial insertion (PI) versus full insertion (FI) depth and when occluding one versus both ears.A descriptive within-subjects design was used in this study.Twenty-two adults with mean four-frequency pure tone averages of 24 dB HL, aged 40–83 yr, participated.BC thresholds were obtained at 250, 500, and 1000 Hz under seven conditions: (1) both ears unoccluded, (2) left ear occluded with PI, (3) right ear occluded with PI, (4) both ears occluded with PI, (5) left ear occluded with FI, (6) right ear occluded with FI, (7) both ears occluded with FI. For PI, one half of the length of the IE was beyond the opening of the ear canal. For FI, the lateral edge of the foam insert was flush with the entrance to the ear canal.Mean OEs were compared with previously published data. In addition, variability in the data was examined using frequency distribution plots as well as cumulative frequency and percentile values.Mean OEs of 5–13 dB were present in all but the FI condition at 1000 Hz where the OE was <3 dB. Differences between PI and FI conditions were present at each frequency measured, irrespective of whether one or both ears were occluded. The shifts in threshold were consistently more prevalent and greater for the PI than the FI conditions overall. Mean differences between the one-ear and both-ears conditions were not clinically significant. Clinically significant variability in the data was noted, except when comparing the one-ear versus both-ears conditions.Occluding the ear during initial BC measurements may artificially improve the thresholds and create or exaggerate an air-bone gap. Thus, initial BC testing should be performed unoccluded at 250, 500, and 1000 Hz. There is a need to account for the OE even when the IE is flush with the ear canal to avoid insufficient masking.