Foam Earplugs Research Articles

A custom-built single-channel in-ear electroencephalography sensor for sleep phase detection: an interdependent solution for at-home sleep studies.

Sleep is vital for health. It has regenerative and protective functions. Its disruption reduces the quality of life and increases susceptibility to disease. During sleep, there is a cyclicity of distinct phases that are studied for clinical purposes using polysomnography (PSG), a costly and technically demanding method that compromises the quality of natural sleep. The search for simpler devices for recording biological signals at home addresses some of these issues. We have reworked a single-channel in-ear electroencephalography (EEG) sensor grounded to a commercially available memory foam earplug with conductive tape. A total of 14 healthy volunteers underwent a full night of simultaneous PSG, in-ear EEG and actigraphy recordings. We analysed the performance of the methods in terms of sleep metrics and staging. In another group of 14 patients evaluated for sleep-related pathologies, PSG and in-ear EEG were recorded simultaneously, the latter in two different configurations (with and without a contralateral reference on the scalp). In both groups, the in-ear EEG sensor showed a strong correlation, agreement and reliability with the 'gold standard' of PSG and thus supported accurate sleep classification, which is not feasible with actigraphy. Single-channel in-ear EEG offers compelling prospects for simplifying sleep parameterisation in both healthy individuals and clinical patients and paves the way for reliable assessments in a broader range of clinical situations, namely by integrating Level 3 polysomnography devices. In addition, addressing the recognised overestimation of the apnea-hypopnea index, due to the lack of an EEG signal, and the sparse information on sleep metrics could prove fundamental for optimised clinical decision making.

Association between personal attenuation rating with types of earplugs and noise exposure levels in a textile factory in China

Objective To investigate the effects of earplug type and noise exposure level on textile workers' personal attenuation rating (PAR). Design Initial and follow-up visits were conducted at a 17-month interval. At each visit, a baseline HPD fit test was performed using either a 3M foam or pre-molded earplug, as chosen by the workers. Workers who failed to meet targeted levels were trained and retested. Once they failed again, the other earplug was selected, and training was provided until they achieved the PAR target. Study sample 192 textile workers into three noise exposure level groups (low, medium, high). Results The median baseline PAR was 10 dB at the initial visits and 13 dB at the follow-up visits, and obtained by foam earplug users was 20 dB, which was higher than that obtained by pre-molded earplug users [12 dB (95% CI, 10–15 dB)]. The highest median baseline PAR was obtained by the high noise level group, followed by the median and low noise level groups. Training significantly increased the PAR. Conclusions Multiple types of earplugs need to be offered to workers to deal with individual differences in attenuation, preferences, and exposure levels. Training and stricter compliance policies can improve HPD use and fitting, contributing to better hearing health.

Measurement and evaluation of personal attenuation rating before and after the training of the noise-exposed workers wearing foam earplugs

Objective: To measure and compare the difference of personal attenuation rating (PAR) of the workers wearing foam earplugs before and after the training, and to evaluate the effect of ear protector wearing training on the noise protection. Methods: In February 2023, 94 workers exposed to noise in a machinery manufacturing factory were selected as subjects. The production noise in the workplace was measured and subjects were trained to wear earplugs. The PAR values of wearing 3M 1110 foam test earplugs were measured and recorded before and after the training by using the fit testing of hearing protection device. The differences between the actual PAR values with nominal values and the noise attenuation values in related standards were compared, and the protective effect of hearing protection device before and after training was evaluated. Results: The average age of the subjects was (36.76±11.48) years old, the average length of service was (16.34±11.64) years, and the average exposure time to noise was (15.67±11.64) years. The noise detection results of the subjects' posts were ranged from 80.1 to 94.3 dB (A). The results of subjects wore 3M 1110 foam test earplugs for fit testing showed that the binaural PAR value after training was (19.3±6.4) dB (A), which was significantly higher than that before training (11.1±7.4) dB (A) (t=13.31, P<0.001). After training, 11 people (11.70%) could reach the corrected noise reduction value (NRR value), 26 people (27.66%) could reach the standard of single noise reduction value (SNR value) ×0.6, and 84 people (89.36%) could reach the standard of (NRR-7) /2. The under protection rate of hearing protectors after training (7.45%) was significantly lower than that before training (45.74%), and the difference of different protection levels before and after training was statistically significant (χ(2)=40.83, P<0.001) . Conclusion: It is suggested that enterprises should use the fit testing instead of nominal value estimation to evaluate the noise reduction effect of hearing protection device. Special training on the selection and use of hearing protection device should be strengthened, so as to ensure that workers wear them correctly and improve the protective effect of hearing protection device.

3D finite element modeling of earplug-induced occlusion effect in the human ear

Poor utilization of earplugs among military personnel may be due to discomfort caused by the occlusion effect (OE). The OE occurs when an earplug occludes the ear canal, thereby changing bone conduction (BC) hearing and amplifying physiological noises from the wearer. There is a need to understand and reduce the OE in the human ear. A 3D finite element model of the human ear including a 3-chambered spiral cochlea was employed to simulate the OE caused by foam and aerogel earplugs. 90 dB sound pressure was applied at the ear canal entrance and BC sound was applied as vibration of the canal bony wall. The model reported the ear canal pressure and the displacements of the stapes footplate and cochlear basilar membrane with and without earplugs. Without BC stimulation, the foam earplug showed a greater pressure attenuation than the aerogel earplug. However, the foam earplug results were more affected by BC stimulation, with a maximum sound pressure increase of 34 dB, compared to the 21.0 dB increase with the aerogel earplug. The aerogel earplug's lower OE demonstrates its promise as an earplug material. Future work with this model will examine BC sound transmission in the cochlea.

Measurement of the local static mechanical pressure of earplugs

Earplugs are used in various critical industrial sectors, such as construction, aviation, military and defense, transportation, and healthcare. However, they present inherent drawbacks, notably discomfort that can lead to inconsistent and incorrect use, thereby leaving a significant proportion of workers vulnerable to irreversible hearing damage, ranging from tinnitus to deafness. This discomfort is closely linked to a physical parameter known as static mechanical pressure (SMP), representing the pressure exerted by earplugs on the earcanal walls. Determining the SMP is crucial for developing earplugs that prioritize comfort. However, experimental studies in this area are scarce and there is no experimental set-up capable of measuring the SMP whether in vivo or ex vivo. The objective of this paper is to fill this gap by presenting a novel experimental system designed to mimic a real earcanal, equipped with an optical probe for precise pressure measurements at various points along the earcanal. This precision-targeted methodology holds the promise of yielding a comprehensive pressure map spanning the entirety of the contact area between the earplug and earcanal, thereby offering unprecedented insights into SMP distribution. To validate our test bench, we conducted experiments using cylindrical rolled-down PVC earplugs inserted into a rigid cylindrical earcanal replica of varying radii. We compared our results with data obtained from a commercially available radial force tester commonly used in investigating stent grafts. Once validation was achieved, we expanded our investigation to measure SMP across various types of earplugs. Additionally, we designed and measured the SMP using roll-down foam earplugs in an artificial earcanal shaped to resemble the human anatomy. Our experimental findings were corroborated with data from finite element method (FEM) numerical calculations. Apart from providing the first comprehensive characterization of the static mechanical pressure exerted by earplugs, our research reveals that with roll-down foam earplugs, increased compression prior to insertion leads to reduced SMP. The versatility of our specially designed test bench allows for mapping SMP caused by earplugs across diverse earcanal shapes. Integration of this instrument into design frameworks holds promise for enhancing the physical comfort of earplugs and, consequently, improving their overall efficacy in hearing protection.

Protecting beyond the bone-conduction limit: Lessons learned developing and fielding a passive Hearing Protection Helmet

Traditional hearing protection devices focus on attenuating air-conducted sound and are limited by the bone conduction threshold (Berger, 1983). In extreme noise fields, such as aircraft maintainers operating near jet engines on aircraft carriers, the bone conducted pathway carries sufficient energy to damage the cochlea. Here, we describe the development, qualification, and field-testing of a passive Hearing Protection Helmet (HPH) designed to surpass the bone conduction limit. The HPH features a noise-isolating shell sealed to the head via a compliant edge seal. When worn with foam earplugs and tested to ANSI S12.6-2016 (Experimenter Fit), the Noise Reduction Rating (NRR) of the HPH is 38 dB and the Noise Reduction Statistic (NRSA) (ANSI S12.68) (80% to 20% of users) is 45 to 52 dB. We also describe challenges associated with user acceptance of the HPH. User feedback led to the integration of an electronic hear-through system to restore auditory situational awareness. Users also rejected wired communication-enabled ear plugs, resulting in the integration of ear cup speakers and adding challenges associated with setting the hear-through sound pressure level limits. We conclude with anecdotes from trial deployments aboard U.S. Navy Aircraft Carriers in 2020, 2022, and 2023.

The Use of Health and Safety Equipment in the Emerald Mines of Swat Valley, Pakistan A Cross-Tabular Descriptive Analysis of Miners’ Views

This study is about the non-use of health and safety equipment in the emerald mines of Swat, Khyber Pakhtunkhwa, Pakistan. The paper draws on the findings of a survey of 300 miners working in the active emerald mines of Swat Valley. The survey was conducted to develop descriptive statistical data about various aspects of miners’ work. However, this paper descriptively presents the findings about the non-use of health and safety equipment in the mines. We sampled 300 gemstone miners from Swat Valley through a convenient sampling technique. The study finds that miners only use protective shoes, hard hats, and, occasionally, hearing conservation. They never use reusable respirators, half-facepiece respirators, full-facepiece respirators, air respirators, push-to-fit earplugs, reusable earplugs, earmuffs, and protective eyewear, thus making them vulnerable to injuries and casualties. Similarly, miners rarely use filter facepiece respirators, disposable respirators, power air-purifying respirators, foam earplugs, and reflective materials as limited to one of a hundred individuals. The use of modern protective equipment could only be ensured if the government takes strict action for the implementation of state policies about mining and by extending financial support and provision of safety equipment at the doorstep of miners.

Contralateral Routing of Signal Disrupts Monaural Sound Localization.

In the absence of binaural hearing, individuals with single-sided deafness can adapt to use monaural level and spectral cues to improve their spatial hearing abilities. Contralateral routing of signal is the most common form of rehabilitation for individuals with single-sided deafness. However, little is known about how these devices affect monaural localization cues, which single-sided deafness listeners may become reliant on. This study aimed to investigate the effects of contralateral routing of signal hearing aids on localization performance in azimuth and elevation under monaural listening conditions. Localization was assessed in 10 normal hearing adults under three listening conditions: (1) normal hearing (NH), (2) unilateral plug (NH-plug), and (3) unilateral plug and CROS aided (NH-plug + CROS). Monaural hearing simulation was achieved by plugging the ear with E-A-Rsoft™ FX™ foam earplugs. Stimuli consisted of 150 ms high-pass noise bursts (3-20 kHz), presented in a random order from fifty locations spanning ±70° in the horizontal and ±30° in the vertical plane at 45, 55, and 65 dBA. In the unilateral plugged listening condition, participants demonstrated good localization in elevation and a response bias in azimuth for signals directed at the open ear. A significant decrease in performance in elevation occurs with the contralateral routing of signal hearing device on, evidenced by significant reductions in response gain and low r2 value. Additionally, performance in azimuth is further reduced for contralateral routing of signal aided localization compared to the simulated unilateral hearing loss condition. Use of the contralateral routing of signal device also results in a reduction in promptness of the listener response and an increase in response variability. Results suggest contralateral routing of signal hearing aids disrupt monaural spectral and level cues, which leads to detriments in localization performance in both the horizontal and vertical dimensions. Increased reaction time and increasing variability in responses suggests localization is more effortful when wearing the contralateral rerouting of signal device.

Using of a Foam Earplug: A Nose Surgery Pearl.

Samaran, Quentin MD*,†; Stoebner, Pierre-Emmanuel MD, PhD†,‡; Ovtchinnikoff, Bernadette MD†,‡ Author Information

Pressure induced by roll-down foam-earplugs on earcanal

Physical discomfort of earplug is a common complaint, so much so it jeopardizes the health and safety of workers, resulting in frequent noncompliance to proper wearing of earplugs. A pressing need thus arises to understand the underlying mechanics for the interaction of earplugs with earcanal walls. An idealized cylindrical geometry of earcanal is first treated with computational and analytical modeling to predict the pressure induced by roll-down cylindrical PVC foam earplugs. In order to predict representative pressure values and distribution, we estimated the hyperelastic properties of foam-based earplugs and characterized their behavior using a stent testing machine (J-CrimpTM machine) that mimics the radial compression of earplugs inside earcanals. Similarly, we estimated the hyperelastic properties of skin based on a simplified model consisting of a single hyperelastic layer. As a crosscheck of those found properties and the calibrated models, we validated them with literature and against a set of three experiments: (i) earplug expansion in a cylindrical holder, (ii) quasi-static uniaxial and (iii) transverse compression. We finally used those validated properties of the foam and skin to compute the pressure magnitude and distribution in an axisymmetric representation of earcanal as well as in a 3D realistic earcanal reconstructed from MRI images of a human subject.

Effect of Hearing Protection Use on Pianists' Performance and Experience: Comparing Foam and Musician Earplugs.

Professional musicians are often exposed to high noise levels and thus face the risk of noise-induced hearing loss. Yet, adoption rates for hearing protection among musicians are low. Previous surveys indicate that the chief concern is the effect of hearing protection use on performance. However, few studies have investigated actual changes in performance when wearing hearing protection. We report an experiment investigating differences in pianists’ performance and experience with and without hearing protection. We compare the effect of foam earplugs and musician earplugs, designed to preserve sound quality with a flat frequency response. The analysis revealed that participants performed overall more loudly with the foam earplugs than with the musician earplugs, and in turn performances with the musician earplugs were louder than the open condition, indicating a compensatory effect. However, this effect was stronger for novel excerpts than for familiar excerpts. No effect was observed on dynamic range. Furthermore, we observed an acclimatization effect, whereby the effect of hearing protection use, observed on the first performance, decreased on the second performance. In terms of experience, participants reported changes in coloration, difficulties gauging dynamics and articulation, and increased effort required when performing with hearing protection. These effects were more pronounced when wearing the foam earplugs, and the participants reported finding the musician earplugs more comfortable to wear and play with. In conclusion, hearing protection use affects pianists’ performance particularly in terms of dynamics and their experience more so in terms of coloration. But the effects are less marked for familiar pieces and after repetition, suggesting that pianists can quickly adjust their playing when playing familiar pieces with hearing protection.

Comfort of earplugs: results of a field survey based on the COPROD questionnaire

Many workers are exposed to noise levels that can cause hearing problems. Earplugs remain a common form of protection for workers exposed to hazardous levels. Their comfort directly affects the effective protection by influencing their consistent and correct use. In order to assess comfort, the COPROD questionnaire was previously developed on the basis of four comfort dimensions: acoustic, physical, functional and psychological. During this field survey, nine earplug models were evaluated by 118 participants over a 6-week period. This paper presents analyses of the collected data and compares three families of earplugs: roll-down foam, premolded and custom moulded. Analyses have shown a better rating of custom moulded earplugs in terms of overall comfort and for all dimensions of comfort. Although premolded earplugs are generally preferred to roll-down foam earplugs, from a statistical point of view, the evaluations of these two families are not significantly different for numerous characteristics. Practitioner Summary: Earplugs comfort conditions the hearing protection of the users. The COPROD questionnaire was developed to jointly evaluate all dimensions of comfort. Nine earplugs models were evaluated by 118 participants during 6 weeks. This paper presents analyses of the collected data.

Evaluation of hearing protection device effectiveness for musicians

Objective To evaluate musicians’ personal attenuation and perceptions of three types of hearing protection devices (HPDs): formable foam earplugs and both non-custom and custom versions of uniform attenuation earplugs (UAEs) marketed to musicians. Design A mixed-methods approach was used to evaluate the HPDs. Audiometric testing obtained hearing levels at baseline and with each HPD across frequencies (125–8000 Hz) to determine personal attenuation ratings and uniformity of attenuation. Participants completed surveys over six months regarding how often they used the HPDs and their perceptions about wearing them. Study sample Twenty-four musicians were recruited to participate. Results Substantial variability was observed in the attenuation achieved among participants for each HPD type, but custom UAEs provided the most consistent attenuation across frequencies. Participants’ HPD preferences were influenced by multiple factors including personal instrument and specific activity. Custom UAEs were most frequently used but usage rates continually decreased over the 6-month period. Conclusions Fit-testing is important to determine fit and sizing. Combining information on the effectiveness of HPDs with musicians’ opinions about wearing them can inform recommendations for which types may be the most effective and feasible options for reducing sound exposures.

A clinical trial of nicergoline to prevent temporary threshold shift

ObjectiveTo evaluate the effectiveness of nicergoline to prevent temporary threshold shift (TTS) in military personnel.Study DesignA randomized control trial.MethodsTwo hundred and twenty‐four participants were enrolled. Nicergoline 30 mg twice daily intake was prescribed to the study group (n = 119) for 3 weeks. The placebo was prescribed to the control group (n = 105) for 3 weeks, as well. Audiometric thresholds were measured at baseline and within 24 h after the participants attended a 1‐day weapons firing practice. During the firing practice, all participants had to wear foam earplugs. The TTS was assessed by using a variety of published significant threshold shift (STS) definitions. Additionally, the effects of the treatment group on the magnitude of pre‐ to postexposure threshold shifts were estimated. Tinnitus and other adverse effects of the medication were recorded.ResultsThe incidence of STS was 65.4% from the study group and 75% from the control group. The negative STS (thresholds improved) was 68.6% from the study group and 44.7% from the control group. The positive STS (thresholds worsened) from the study group and the control group was 31.4% and 55.3%, respectively. The effect of treatment in participants receiving nicergoline demonstrated significant coefficients (change in dB) in both ears (p = .001). The mean different threshold of participants receiving nicergoline showed negative STS in all tested frequencies without statistical significance. However, the mean different threshold of participants receiving a placebo showed positive STS with statistical significance. Additionally, there were 16 ears detecting a warning sign of permanent hearing loss. These participants from the control group presented a longer duration of tinnitus (p = .042). Moreover, the serious adverse effects of nicergoline were considerably low.ConclusionThe study results suggest that nicergoline may attenuate noise‐related TTS and tinnitus, and justify further investigation on the effectiveness of this drug as an otoprotectant.Level of Evidence2

The efficacy of earplugs at a major hazard facility.

At a major hazard facility, cases of occupational noise-induced hearing loss have occurred despite the use of hearing protection devices. Preliminary measurements of personal attenuation ratings (PAR) suggested that earplugs may not achieve the attenuation implied by their Australian SLC80 Class designation in field-use conditions. We examined the relationship between PAR and the SLC80 classification for earplugs, as a good understanding of the attenuation provided by earplugs under normal field-use conditions, rather than in laboratory settings, is vital to their effective use as a control measure for noise exposure. A cross-sectional study was performed with 65 volunteers. Participants were recruited from Operations and Maintenance Technicians at the major hazard facility. The participants had their PARs checked with different earplug types using the 3M™ E-A-Rfit™ system. We examined the PARs measured and also assigned a 'pass' or 'fail' rating depending on whether the earplug achieved 22dB attenuation. 22dB attenuation for 80% of users is the minimum to meet the definition for Australian SLC80 Class 4 hearing protection. None of the earplug types achieved 22dB attenuation for 80% of users when tested in field-use conditions. There were statistically significant differences in the frequency of achieving a 'Pass', and in PAR, depending on earplug type. Roll-down foam earplugs may provide superior attenuation compared to pre-moulded earplugs. Earplugs are unlikely to achieve the attenuation found in laboratory conditions during field-use. Personalised selection of hearing protection devices based on fit-testing results should be encouraged.

Temporary Unilateral Hearing Loss Impairs Spatial Auditory Information Processing in Neurons in the Central Auditory System.

Temporary conductive hearing loss (CHL) can lead to hearing impairments that persist beyond resolution of the CHL. In particular, unilateral CHL leads to deficits in auditory skills that rely on binaural input (e.g., spatial hearing). Here, we asked whether single neurons in the auditory midbrain, which integrate acoustic inputs from the two ears, are altered by a temporary CHL. We introduced 6 weeks of unilateral CHL to young adult chinchillas via foam earplug. Following CHL removal and restoration of peripheral input, single-unit recordings from inferior colliculus (ICC) neurons revealed the CHL decreased the efficacy of inhibitory input to the ICC contralateral to the earplug and increased inhibitory input ipsilateral to the earplug, effectively creating a higher proportion of monaural responsive neurons than binaural. Moreover, this resulted in a ∼10 dB shift in the coding of a binaural sound location cue (interaural-level difference, ILD) in ICC neurons relative to controls. The direction of the shift was consistent with a compensation of the altered ILDs due to the CHL. ICC neuron responses carried ∼37% less information about ILDs after CHL than control neurons. Cochlear peripheral-evoked responses confirmed that the CHL did not induce damage to the auditory periphery. We find that a temporary CHL altered auditory midbrain neurons by shifting binaural responses to ILD acoustic cues, suggesting a compensatory form of plasticity occurring by at least the level of the auditory midbrain, the ICC.

Detection thresholds with active hearing protection devices in quiet and noise

The Real-Ear Attenuation at Threshold (REAT) method is a standardized (ANSI/ASA S12.6) method of assessing the passive attenuation of hearing protection devices (HPD), including electronic HPDs with the electronics turned off. Characterizing HPDs with electronics turned on is performed with the Microphone in Real Ear (MIRE) method, or with an acoustic test fixture, as described in ANSI/ASA S12.42. It has been proposed that the REAT method may be useful for characterizing the effect of HPDs on detection of ambient sounds for HPDs with hear-through microphones, including the effects of electronics noise from the HPD. In this study, detection thresholds were measured with three electronic earmuff-type HPDs using a method similar to the REAT method. Detection thresholds were obtained for warble tones presented from a loudspeaker placed in front of the subject in a sound treated room. Thresholds were measured with unoccluded ears and with three HPDs with hear-through capability in quiet and in noise. In addition, thresholds were measured with one of the HPDs with foam earplugs inserted into both ears to simulate a conductive hearing loss. The results point to the interaction between device noise, ambient noise, and human absolute thresholds as limitations on the detectability of ambient sounds.

The Effect of Wearing Foam and Etymotic Earplugs on Classical Musicians’ Pitch Perception

The purpose of this study was to investigate the effect of wearing earplugs on classical musicians’ pitch perception across three experimental conditions: no earplugs, foam earplugs, and Etymotic earplugs. Participants were graduate and undergraduate music majors attending a large school of music in the southeastern United States ( N = 72). Participants adjusted the pitch of five complex stimulus tones (C#4, C#5, C#3, G#4, and F#3) using a continuous response digital interface until they believed the interval was in tune with an oboe (C#4) reference tone. Participants tended to tune flat when the stimulus tone was presented flat and to tune sharp when it was presented sharp across all three earplug conditions. Overall cent deviation in tuning responses showed that in both directional and absolute deviation analyses, listeners were most accurate when tuning without earplugs, then when using Etymotic earplugs, and least accurate with foam earplugs. Significant differences, however, were limited to specific intervals and in magnitudes not likely to be perceived. Although more research is needed, the use of Etymotic earplugs may provide valuable protection against noise-induced hearing loss with negligible effects on pitch perception. Implications for musicians and recommendations for future research are discussed.

Dual-laser measurement of human stapes footplate motion under blast exposure

Hearing damage is one of the most frequently observed injuries in Service members and Veterans even though hearing protection devices (HPDs, e.g. earplugs) have been implemented to prevent blast-induced hearing loss. However, the formation and prevention mechanism of the blast-induced hearing damage remains unclear due to the difficulty for conducting biomechanical measurements in ears during blast exposure. Recently, an approach reported by Jiang et al. (2019) used two laser Doppler vibrometers (LDVs) to measure the motion of the tympanic membrane (TM) in human temporal bones during blast exposure. Using the dual laser setup, we further developed the technology to detect the movement of the stapes footplate (SFP) in ears with and without HPDs while under blast exposure.Eight fresh human cadaveric temporal bones (TBs) were involved in this study. The TB was mounted in a “head block” after performing a facial recess surgery to access the SFP, and a pressure sensor was inserted near the TM in the ear canal to measure the pressure reaching the TM (P1). The TB was exposed to a blast overpressure measuring around 7 psi or 48 kPa at the entrance of the ear canal (P0). Two LDVs were used to measure the vibrations of the SFP and TB (as a reference). The exact motion of the SFP was determined by subtracting the TB motion from the SFP data.Results included a measured peak-to-peak SFP displacement of 68.7 ± 31.6 μm (mean ± SD) from all eight TBs without HPDs. In five of the TBs, the insertion of a foam earplug reduced the SFP displacement from 48.3 ± 6.3 μm to 21.8 ± 10.4 μm. The time-frequency analysis of the SFP velocity signals indicated that most of the energy spectrum was concentrated at frequencies below 4 kHz within the first 2 ms after blast and the energy was reduced after the insertion of HPDs.This study describes a new methodology to quantitatively characterize the response of the middle ear and the energy entering the cochlea during blast exposure. The experimental data are critical for determining the injury of the peripheral auditory system and elucidating the damage formation and prevention mechanism in an ear exposed to blast.

Field Attenuation of Foam Earplugs.

BackgroundHearing protection devices (HPDs) are often used in the workplace to prevent hearing damage caused by noise. However, a factor that can lead to hearing loss in the workplace is improper HPD fitting, and the previous literature has shown that instructing workers on how to properly insert their HPDs can make a significant difference in the degree of attenuation.MethodsTwo studies were completed on a total of 33 Hydro One workers. A FitCheck Solo field attenuation estimation system was used to measure the personal attenuation rating (PAR) before and after providing one-on-one fitting instructions. In addition, external ear canal diameters were measured, and a questionnaire with items related to frequency of use, confidence, and discomfort was administered.ResultsTraining led to an improvement in HPD attenuation, particularly for participants with poorer PARs before training. The questionnaire results indicated that much HPD discomfort is caused by heat, humidity, and communication difficulties. External ear canal asymmetry did not appear to significantly influence the measured PAR.ConclusionIn accordance with the previous literature, our studies suggest that one-on-one instruction is an effective training method for HPD use. Addressing discomfort issues from heat, humidity, and communication issues could help to improve the use of HPDs in the workplace. Further research into the effects of canal asymmetry on the PAR is needed.