Kristy K. Deiters

Typical noise exposure in daily life

Abstract Objective: Identify the distribution of typical noise levels present in daily life and identify factors associated with average sound levels. Design: This was an observational study. Study sample: Participants (N = 286) were 20 to 68 year old men and women, drawn from the general population of Kalamazoo County, Michigan. A total of 73 000 person-hours of noise monitoring were conducted. Results: Median overall daily average levels were 79 and 77 dBLeqA,8,equiv , with average levels exceeding EPA recommended levels for 70% of participants. Median levels were similar between the hours of 9 a.m. and 9 p.m., and varied little across days of the week. Gender, occupational classification, and history of occupational noise exposure were related to average noise levels, but age, educational attainment, and non-occupational noise exposures were not. Conclusions: A large portion of the general population is exposed to noise levels that could result in long-term adverse effects on hearing. Gender and occupation were most strongly related to exposure, though most participants in this study had occupations that are not conventionally considered noisy.

Short-term variability of pure-tone thresholds obtained with TDH-39P earphones.

Abstract Objective: To estimate the short-term variability and correlates of variability in pure-tone thresholds obtained using audiometric equipment designed for occupational use, and to examine the justification for excluding 8 kHz as a mandatory threshold in occupational hearing conservation programs. Method: Pure-tone thresholds and other hearing-related tests (e.g. noise dosimetry, otoscopy, middle-ear assessment) were conducted with a group of 527 adults between 20 and 69 years of age. Five measurement visits were completed by participants within 14 days. Results: The 50% critical difference boundaries were − 5 and 0 dB at 4 kHz and below and − 5 and 5 dB at 6 and 8 kHz. The likelihood of spurious notches due to test-retest variability was substantially lower than the likelihood of failing to detect a notched configuration when present. Correlates of variability included stimulus frequency, baseline threshold, acoustic reflectance of the ear, average noise exposure during the previous eight hours, age, and the testers level of education in audiology. Conclusion: The short-term variability in 8-kHz pure-tone thresholds obtained with the TDH-39P earphone was slightly greater than at other frequencies, but this difference was not large enough to justify the disadvantages stemming from the inability to detect a 6-kHz notch.

Acoustic reflexes are common but not pervasive: evidence from the National Health and Nutrition Examination Survey, 1999–2012

Abstract Objective: To determine whether acoustic reflexes are pervasive (i.e. sufficiently prevalent to provide 95% confidence of at least 95% prevalence) and might be invoked in damage-risk criteria (DRC) and health hazard assessments (HHA) for impulsive noise. Design: Cross-sectional analyses of a nationally-representative study. Study sample: National Health and Nutrition Examination Survey (NHANES) data collected between 1999 and 2012 were used. Over 60 thousand reflex traces obtained from 15,106 NHANES participants were used in the study, along with demographic, audiometric, health and exposure variables obtained in that study. Results: Acoustic reflexes were not sufficiently prevalent to be deemed pervasive by any detection method or in any subgroup defined by age or audiometric characteristics. The odds of observing acoustic reflexes were greater for women, young adults, and people with better hearing sensitivity. Abnormally high tympanometric admittance and “Other” race/ethnicity (i.e. people who do not self-identify as exclusively Non-Hispanic White, Non-Hispanic Black, Mexican–American, or Hispanic) were associated with lower odds. Conclusions: Acoustic reflexes are not sufficiently prevalent to be included in DRC and HHA for impulsive noise.

Stimulus and transducer effects on threshold

Abstract Objective: This study examined differences in thresholds obtained under Sennheiser HDA200 circumaural earphones using pure tone, equivalent rectangular noise bands, and 1/3 octave noise bands relative to thresholds obtained using Telephonics TDH-39P supra-aural earphones. Design: Thresholds were obtained via each transducer and stimulus condition six times within a 10-day period. Study sample: Forty-nine adults were selected from a prior study to represent low, moderate, and high threshold reliability. Results: The results suggested that (1) only small adjustments were needed to reach equivalent TDH-39P thresholds, (2) pure-tone thresholds obtained with HDA200 circumaural earphones had reliability equal to or better than those obtained using TDH-39P earphones, (3) the reliability of noise-band thresholds improved with broader stimulus bandwidth and was either equal to or better than pure-tone thresholds, and (4) frequency-specificity declined with stimulus bandwidths greater than one equivalent rectangular band, which could complicate early detection of hearing changes that occur within a narrow frequency range. Conclusions: These data suggest that circumaural earphones such as the HDA200 headphones provide better reliability for audiometric testing as compared to the TDH-39P earphones. These data support the use of noise bands, preferably ERB noises, as stimuli for audiometric monitoring.

Prevalence of acoustic reflexes in the United States

The acoustic reflex is a contraction of the middle ear muscles in response to high-level sounds. Acoustic reflexes are invoked as a protective mechanism in some damage-risk criteria (DRC). However, acoustic reflexes are not always observed among people without auditory dysfunction, and should not be included in DRC unless there is 95% certainty that 95% of the population have acoustic reflexes. In the current study, we present the prevalence of acoustic reflexes among people 12 years and older (N > 11,400), using data from the National Health and Nutrition Examination Survey (NHANES). The NHANES can be used to produce prevalence estimates generalizable to the non-institutionalized U.S. population. Ipsilateral reflexes were screened at two elicitor frequencies and detected using Frequentist methods and via Kalman filtering of the reflex trace. Reflexes are pervasive only among those with hearing thresholds better than 15 dB HL at all frequencies, and fall below the criterion certainty with poorer sensitivity even at lower frequencies. Age and tympanometric variables are also related to reflex detection. Reflex prevalence is generally high among young people with adequate hearing sensitivity for unrestricted military duty, but the prevalence is not uniform among audiometric configurations within this hearing profile.

Have the NIOSH age correction tables gone stale

Occupational Hearing Conservation programs permit subtracting cross-sectional trends in hearing sensitivity from the changes observed with an exposed worker. Regulatory agencies in the U.S. define the expected cross-sectional trend using the NIOSH age correction tables, which summarized mean differences in comparatively small groups of men and women 50 years ago. At all ages, hearing sensitivity is better now than it was 50 years ago, and important demographic characteristics (e.g., race/ethnicity) that predict cross-sectional trends were not included in the NIOSH tables. Quantile regression results from the National Health and Nutrition Examination Survey (NHANES) were used to derive revised age correction tables that can be applied to men or women across a wider range of ages and race/ethnicity categories. These age correction tables and comparisons with the prior NIOSH tables will be presented.Occupational Hearing Conservation programs permit subtracting cross-sectional trends in hearing sensitivity from the changes observed with an exposed worker. Regulatory agencies in the U.S. define the expected cross-sectional trend using the NIOSH age correction tables, which summarized mean differences in comparatively small groups of men and women 50 years ago. At all ages, hearing sensitivity is better now than it was 50 years ago, and important demographic characteristics (e.g., race/ethnicity) that predict cross-sectional trends were not included in the NIOSH tables. Quantile regression results from the National Health and Nutrition Examination Survey (NHANES) were used to derive revised age correction tables that can be applied to men or women across a wider range of ages and race/ethnicity categories. These age correction tables and comparisons with the prior NIOSH tables will be presented.

Anticipatory middle ear muscle contractions in damage-risk criteria

Anticipatory middle ear muscle contractions (MEMC) have been implemented as protective components of Damage-Risk Criteria (DRC) for impulsive noises. However, no studies have shown that anticipatory MEMC are pervasive among humans. This presentation describes a series of studies of the viability of assumed anticipatory MEMC obtained either through classical conditioning or while operating a model gun. Participants were adults with normal hearing, and the conditioning tasks varied on sensory modality and attention. Both between- and within-subjects designs were used. A conditioned response was defined as an MEMC occurring prior to the unconditioned stimulus and when only the conditioning stimulus was presented. These studies do not suggest that anticipatory MEMC should be included in DRC for impulsive noises.

Acoustic reflexes are common but not pervasive: evidence using a diagnostic middle ear analyser

Abstract Objective: The objective of this study is to determine whether acoustic reflexes are pervasive (i.e. known with 95% confidence to be observed in at least 95% of people) by examining the frequency of occurrence using a friction-fit diagnostic middle ear analyser. Design: Adult participants with very good hearing sensitivity underwent audiometric and middle ear testing. Acoustic reflexes were tested ipsilaterally and contralaterally in both ears across a range of elicitor frequencies. Reflex elicitors were 700 ms tones presented at maximum level of 100 dB HL. Two automated methods were used to detect the presence of an acoustic reflex. Study sample: A group of 285 adult volunteers with normal hearing. Results: There were no conditions in which the proportion of participants exhibiting acoustic reflexes was high enough to be deemed pervasive. Ipsilateral reflexes were more likely to be observed than contralateral reflexes and reflexes were more common at 0.5 and 1 kHz elicitor frequencies as compared with 2 and 4 kHz elicitor frequencies. Conclusions: Acoustic reflexes are common among individuals with good hearing. However, acoustic reflexes are not pervasive and should not be included in damage risk criteria and health hazard assessments for impulsive noise.

Middle ear muscle contractions from non-acoustic elicitors

High-level sounds can elicit middle ear muscle contractions (MEMC), which are commonly known as acoustic reflexes. Tactile stimulation to the face can also elicit MEMC, and it is plausible that MEMC could co-occur with voluntary eye closure gestures. In this paper, we shall present preliminary MEMC results from human volunteers receiving controlled tactile stimulation (nitrogen gas, 10 kPa, 200 ms duration) to four locations on the face and who close the eye ipsilateral to the MEMC detection probe. The MEMC were detected via changes in total energy reflected in the ear using a filtered (0.2 to 8 kHz) click train. Concomitant muscle activity was measured using electromyography. The morphology and magnitude of the MEMC from these non-acoustic stimuli will be described. If non-acoustic MEMC behaviors do not extinguish and are not highly susceptible to fatigue, they could represent an opportunity to mediate exposure to short-duration noises or help explain between-person differences in noise exposure outcomes.

Assessing acoustic reflexes for impulsive sound

The acoustic reflex is an involuntary contraction of the middle ear muscles in response to a variety of sensory and behavioral conditions. Middle ear muscle contractions (MEMC) have been invoked in some damage-risk criteria for impulsive noises for over 40 years and one damage-risk criteria proposes that MEMC precede the impulse for a warned listener via response conditioning. However, empirical data describing the prevalence, magnitude, and time-course of reflexive MEMC elicited by impulsive stimuli as well as non-acoustic stimuli and behaviors are scant. Likewise, empirical support for anticipatory MEMC is limited and studies often fail to control for attention or concomitant muscle activity. The current study is a large-scale, multi-experiment project designed to address these limitations in a laboratory and field environment. MEMC are detected using click train stimuli as probes. Reflexive MEMC are elicited using tones, recorded gunshots, and non-acoustic stimuli (e.g., controlled release of compresse...