Mark R. Stephenson

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.

Hearing loss prevention for carpenters: part 2 - demonstration projects using individualized and group training.

Two demonstration projects were conducted to evaluate the effectiveness of a comprehensive training program for carpenters. This training was paired with audiometry and counseling and a survey of attitudes and beliefs in hearing loss prevention. All participants received hearing tests, multimedia instruction on occupational noise exposure/hearing loss, and instruction and practice in using a diverse selection of hearing protection devices (HPDs). A total of 103 apprentice carpenters participated in the Year 1 training, were given a large supply of these HPDs, and instructions on how to get additional free supplies if they ran out during the 1-year interval between initial and follow-up training. Forty-two participants responded to the survey a second time a year later and completed the Year 2 training. Significant test-retest differences were found between the pre-training and the post-training survey scores. Both forms of instruction (individual versus group) produced equivalent outcomes. The results indicated that training was able to bring all apprentice participants up to the same desired level with regard to attitudes, beliefs, and behavioral intentions to use hearing protection properly. It was concluded that the health communication models used to develop the educational and training materials for this effort were extremely effective.

Effects of training on hearing protector attenuation

The effect of training instruction, whether presented as the manufacturers printed instructions, a short video training session specific to the product, or as a one-on-one training session was evaluated using four hearing protection devices with eight groups of subjects. Naïve subjects were recruited and tested using three different forms of training: written, video, and individual training. The group averages for A-weighted attenuation were not statistically significant when compared between the video or the written instruction conditions, regardless of presentation order. The experimenter-trained A-weighted attenuations were significantly greater than the written and video instruction for most of the protectors and groups. For each earplug, the noise reduction statistic for A-weighting (NRS A ) and the associated confidence intervals were calculated for the 80 th and 20 th percentiles of protection. Across subject groups for each protector, the differences between NRS A ratings were found to be not statistically significant. Several comparisons evaluating the order of testing, the type of testing, and statistical tests of the performance across the groups are presented.

Hearing loss prevention for carpenters: Part 1 - Using health communication and health promotion models to develop training that works

In phase 1 of a large multiyear effort, health communication and health promotion models were used to develop a comprehensive hearing loss prevention training program for carpenters. Additionally, a survey was designed to be used as an evaluation instrument. The models informed an iterative research process in which the authors used key informant interviews, focus groups, and early versions of the survey tool to identify critical issues expected to be relevant to the success of the hearing loss prevention training. Commonly held attitudes and beliefs associated with occupational noise exposure and hearing losses, as well as issues associated with the use or non-use of hearing protectors, were identified. The training program was then specifically constructed to positively shape attitudes, beliefs, and behavioral intentions associated with healthy hearing behaviors - especially those associated with appropriate hearing protector use. The goal was to directly address the key issues and overcome the barriers identified during the formative research phase. The survey was finalized using factor analysis methods and repeated pilot testing. It was designed to be used with the training as an evaluation tool and thus could indicate changes over time in attitudes, beliefs, and behavioral intentions regarding hearing loss prevention. Finally, the training program was fine tuned with industry participation so that its delivery would integrate seamlessly into the existing health and safety training provided to apprentice carpenters. In phase 2, reported elsewhere in this volume, the training program and the survey were tested through a demonstration project at two sites.

The effects of training format on earplug performance

This experiment investigated the effect of small-group versus individual hearing loss prevention (HLP) training on the attenuation performance of passive insert-type hearing protection devices (HPDs). A subject-fit (SF) methodology, which gave naive listeners access only to the instructions printed on the HPD product label, was used to determine real-ear attenuation at threshold (REAT) at third-octave noise bands between 125–8000 Hz. REAT measurements were augmented by use of the Hearing Loss Prevention Attitude-Belief (HLPAB) survey, a field-tested self-assessment tool developed by the National Institute for Occupational Safety and Health (NIOSH). Participants were randomly assigned to one of four experimental groups, consisting of 25 listeners each, in a controlled behavioral-intervention trial. There were two types of HPDs (formable and premolded) and two training formats (individual and small group). A short multimedia program, including a practice session, was presented to all 100 listeners. Results showed training to have a significant effect, for both HPDs on real-ear attenuation and attitude, but, importantly, there was no difference between small-group and individual training.

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.

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.

Early prognosis of noise-induced hearing loss: prioritising prevention over prediction

Moshammer et al 1 have recommended routine implementation of a temporary threshold shift (TTS) screening test to identify workers particularly at risk of developing noise-induced hearing loss (NIHL) from occupational exposure to hazardous noise. Their work addresses an important occupational health problem. NIHL ranks among the most common work-related injuries in many countries, with an estimated global annual incidence of 1.6 million cases, and accounts for approximately 16% of disabling adult hearing losses worldwide.2 ,3 Individuals vary in their susceptibility to the damaging effects of noise and no suitable method currently exists to predict the susceptibility of a particular worker. In their study, Moshammer et al measured TTS in newly hired employees following exposure to a 20 min, high-intensity, low-frequency experimental noise. They then followed the workers over time to see who ultimately developed a permanent threshold shift (PTS). The authors report that a TTS of 14 dB or more measured 2.5 min after the experimental exposure identifies workers at greater risk for PTS. They recommend routinely using this procedure to screen for susceptibility to noise in workplace hearing loss prevention programmes. However, this recommendation is premature in view of the study results. The TTS measure had a sensitivity of 82%, meaning that 18% of those who developed PTS were not identified by the TTS screening—a …

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.

Occupational Hearing Loss from Non-Gaussian Noise

For millennia, we have known that loud noise can harm hearing. However, defining the specific hearing risk posed by a specific noise for a specific individual is still elusive. Many factors influence whether or not a given noise is harmful. Attempts to quantify this potential harm began in earnest after World War II, when many veterans returned to their civilian lives with service-connected hearing loss. Database analyses, laboratory studies of permanent and temporary threshold shifts in animals, and laboratory studies of temporary threshold shifts in humans led to the first recommended hearing damage-risk criteria and corresponding hearing conservation programs in the 1950s. Not unexpectedly, as our ability to measure and monitor both noise exposures and their effects on humans and animals has evolved, recommended hearing damage-risk criteria and hearing loss prevention practices also have evolved. Between the early 1970s and late 1990s, several regulations and national standards were promulgated, which have profoundly influenced policies and practices regarding noise exposure. These include the U.S. Environmental Protection Agency 1974 recommendations for community and environmental noise exposures (EPA/ONAC 550/9-74-004), the U.S. Occupational Safety and Health Administration 1983 occupational noise exposure standard (29 CFR 1910.95), the International Organization for Standardization standard for estimation of noise-induced hearing loss (ISO 1999), and the U.S. National Institute for Occupational Safety andHealth (NIOSH) 1972 and 1998 criteria documents on occupational noise exposure (NIOSH 73-11001 and 98-126). Because of the widespread use and acceptance of these guidelines, it has become “business as usual” for noise-exposed workers to be enrolled in occupational hearing conservation programs. Likewise, many community leaders and individuals engaged in noisy recreational activities have a heightened awareness of the harmful effects of loud noise, which has led to the establishment of community noise standards and use of personal hearing protection, respectively. However, it would be a very serious mistake to conclude that the hearing loss prevention profession now has all the technical tools and professional guidelines necessary to effectively prevent noise-induced hearing loss. In particular, existing noise exposure guidelines have addressed mainly continuous and steady state (Gaussian) noise. Intermittent exposures, impulsive noise, and combinations of noise exposures (termed “complex” or “non-Gaussian” noise) have received much less attention. However, recent advances in noise measurement instrumentation and methods, as well as the introduction of newmetrics to characterize complex, non-Gaussian noise, now enable study of the relationship between these noises andhearing damage risk. As a result, hearing conservationists can begin to work toward establishing guidelines for preventing hearing loss from time-varying, impulsive, or combined noise exposures. At the same time, new research has found that the physiological effects of noise may extend beyond the outer hair cells of the cochlea to the synapse between the hair cells and auditory neurons. This damage—known as synaptopathy—can create a “hidden” hearing loss not evident on the pure tone audiogram.