Case reports can be informative.
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Adult↗
SEARCH · PubMed Health
Results for “Ear Protective Devices”
Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.
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Reducing persistent auditory hallucinations by wearing an ear-plug.
A case study is presented of the effects of wearing an ear-plug in a single patient with persistent auditory hallucinations. Beneficial effects were detected when the plug was in the dominant ear only.
Adult↗
Electrodynamic headphones and woofers for application in magnetic resonance imaging scanners.
Electrodynamic speakers compatible with (functional) magnetic resonance imaging (MRI) are described. The speakers magnets are removed, their function is replaced by the scanner's magnetic field, resulting in an uncommon but efficient operation. The method can be used with headphones as well as woofers. Functional MRI is not associated with any known biological risks, but as a method for visualization of task-specific activation of brain regions it is undesirably noisy. Thus, it requires both noise protection and efficient sound transmission systems for delivering acoustic stimuli to subjects. Woofers could possibly be used in active noise-control systems. The speakers described in this paper can be used for either task.
Acoustics↗
Hearing protector attenuation: models of attenuation distributions.
Current hearing protector rating standards estimate the protection performance for a given frequency as the mean attenuation minus a multiple of the standard deviation. Distributions of real-ear attenuation at threshold data are fit with maximum likelihood estimation procedures using both normal and mixed-normal models. Attenuations from six hearing protectors, Bilsom UF-1 earmuff, Bilsom Quietzone, E.A.R Classic, E.A.R EXPRESS Pod Plugs, Howard Leight MAX, and Wilson EP100 earplugs, measured with a subject-fit protocol are reported. The mixed-normal (bimodal) model provides a better fit to the empirical data than the unimodal model for most frequencies and protectors. Primarily, the bimodal model fits the shape of the distributions caused by data from poorly-fit protectors. This paper presents an alternative method for estimating the protection performance either with the more accurate bimodal model or directly from the empirical cumulative distributions of the attenuation data.
Auditory Threshold↗
Combined feedback-feedforward active noise-reducing headset--the effect of the acoustics on broadband performance.
Active noise-reducing headsets that employ analog feedback control and provide good broadband attenuation are commercially available for a wide range of applications. Recent studies have explored the integration of an adaptive digital feedforward controller with the analog feedback controller to provide additional attenuation of periodic noise components. This paper presents an experimental study of such a combined control system, but with both feedback- and feedforward controllers attenuating broadband noise. Good performance is demonstrated in a reverberant sound field, while under direct sound-field conditions the attenuation performance of the feedforward controller is shown to be dependent on head position. The paper concludes with an analysis of the forward path delay showing how the passive attenuation mechanism improves broadband performance.
Computers↗
Novel active noise-reducing headset using earshell vibration control.
Active noise-reducing (ANR) headsets are available commercially in applications varying from aviation communication to consumer audio. Current ANR systems use passive attenuation at high frequencies and loudspeaker-based active noise control at low frequencies to achieve broadband noise reduction. This paper presents a novel ANR headset in which the external noise transmitted to the user's ear via earshell vibration is reduced by controlling the vibration of the earshell using force actuators acting against an inertial mass or the earshell headband. Model-based theoretical analysis using velocity feedback control showed that current piezoelectric actuators provide sufficient force but require lower stiffness for improved low-frequency performance. Control simulations based on experimental data from a laboratory headset showed that good performance can potentially be achieved in practice by a robust feedback controller, while a single-frequency real-time control experiment verified that noise reduction can be achieved using earshell vibration control.
Ear Protective Devices↗
Hearing protection: surpassing the limits to attenuation imposed by the bone-conduction pathways.
With louder and louder weapon systems being developed and military personnel being exposed to steady noise levels approaching and sometimes exceeding 150 dB, a growing interest in greater amounts of hearing protection is evident. When the need for communications is included in the equation, the situation is even more extreme. New initiatives are underway to design improved hearing protection, including active noise reduction (ANR) earplugs and perhaps even active cancellation of head-borne vibration. With that in mind it may be useful to explore the limits to attenuation, and whether they can be approached with existing technology. Data on the noise reduction achievable with high-attenuation foam earplugs, as a function of insertion depth, will be reported. Previous studies will be reviewed that provide indications of the bone-conduction (BC) limits to attenuation that, in terms of mean values, range from 40 to 60 dB across the frequencies from 125 Hz to 8 kHz. Additionally, new research on the effects of a flight helmet on the BC limits, as well as the potential attenuation from deeply inserted passive foam earplugs, worn with passive earmuffs, or with active-noise reduction (ANR) earmuffs, will be examined. The data demonstrate that gains in attenuation exceeding 10 dB above the head-not-covered limits can be achieved if the head is effectively shielded from acoustical stimulation.
Auditory Threshold↗
The effects of single and double hearing protection on the localization and segregation of spatially-separated speech signals.
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Adult↗
Hybrid feedforward-feedback active noise reduction for hearing protection and communication.
A hybrid active noise reduction (ANR) architecture is presented and validated for a circumaural earcup and a communication earplug. The hybrid system combines source-independent feedback ANR with a Lyapunov-tuned leaky LMS filter (LyLMS) improving gain stability margins over feedforward ANR alone. In flat plate testing, the earcup demonstrates an overall C-weighted total noise reduction of 40 dB and 30-32 dB, respectively, for 50-800 Hz sum-of-tones noise and for aircraft or helicopter cockpit noise, improving low frequency (<100 Hz) performance by up to 15 dB over either control component acting individually. For the earplug, a filtered-X implementation of the LyLMS accommodates its nonconstant cancellation path gain. A fast time-domain identification method provides a high-fidelity, computationally efficient, infinite impulse response cancellation path model, which is used for both the filtered-X implementation and communication feedthrough. Insertion loss measurements made with a manikin show overall C-weighted total noise reduction provided by the ANR earplug of 46-48 dB for sum-of-tones 80-2000 Hz and 40-41 dB from 63 to 3000 Hz for UH-60 helicopter noise, with negligible degradation in attenuation during speech communication. For both hearing protectors, a stability metric improves by a factor of 2 to several orders of magnitude through hybrid ANR.
Aircraft↗
Hearing protector rating.
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Ear Protective Devices↗
Speech intelligibility in noise: effects of fluency and hearing protector type.
This research investigated the effect of car protectors on the intelligibility of speech in noise. Listeners with normal hearing, high-frequency, and flat loss were tested. Half the subjects in each group were fluent in English and half-poorly conversant. Taped lists of 25 words were presented free field under conditions defined by the speech-to-noise ratio, spectrum of noise background, and presence of ear protection. The results showed that intelligibility decreased with speech-to-noise ratio and was poorer in crowd noise than in white noise. The protector had no effect for the normal listener, but caused a substantial decrement in those with impairment. In all groups nonfluency contributed an additional loss of 10% to 20%. Significant differences in performance were noted for different muff and plug types.
Adult↗
A psychophysical evaluation of the dependence of hearing protector attenuation on noise level.
The attenuation characteristics of ten commercially available hearing protectors (five muffs and five plugs) were examined for 1/3-octave bands of noise centered at 1000, 2000, 3150, 4000, and 6300 Hz in ten normal-hearing young adults utilizing four psychophysical procedures. One of these procedures, the real-ear attenuation at threshold procedure described in the American standard for the evaluation of hearing protectors, is designed for use at 1/3-octave band noise levels below approximately 50 dB SPL. Three real-ear psychophysical procedures were also developed and evaluated. These procedures were: (1) a reaction-time paradigm; (2) a loudness magnitude-estimation procedure; and (3) a masked bone-conduction threshold technique. Each procedure was designed to evaluate protectors for 1/3-octave bands of noise having levels ranging from approximately 50 to 90 dB SPL. Mean data indicated that: (1) attenuation was linear over the range investigated, although some exceptions to this generalization were apparent; (2) attenuation estimates derived with the reaction-time and magnitude-estimation paradigms were typically less than those obtained with the other two methods; and (3) all attenuation estimates, regardless of procedure, were less than manufacturer's specifications for the majority of the protectors. Implications for existing standards are discussed.
Auditory Threshold↗
Sound attenuation of TDH-39 earphones in a diffuse field of narrow-band noise.
The sound attenuation characteristics of the audiometric earphone Telephonics TDH-39 with cushion MX-41/AR have been tested, using the hearing threshold method according to the International Standard ISO 4869-1981 ("Acoustics--Measurement of sound attenuation of hearing protectors--Subjective method"). This method specifies 1/3-oct bands of noise as test signals and a diffuse sound field. This is in contrast to the use of pure tones in a frontally incident free sound field, by means of which most earlier attenuation data have been obtained. The mean sound attenuation values obtained from a group of 20 normal-hearing subjects were up to 3-5 dB lower than those previously reported for pure tones in a free field.
Adolescent↗
Measuring helmet sound attenuation characteristics using an acoustic manikin.
The sound attenuation characteristics of two military helmets were measured using an acoustic manikin as the test apparatus. The manikin results are compared to the results of attenuation measurements made on human subjects wearing identical helmets. The testing room and instrumentation were the same for both the manikin and human subjects. Procedures in ANSI S3.19-1974 were used in the real-ear attentuation at threshold (REAT) part of this study. The results are encouraging as they suggest that the manikin may be used in place of a panel of human subjects to evaluate the hearing protection characteristics of military head gear.
Acoustics↗
Reference thresholds for the ER-3A insert earphone.
Several recent studies have demonstrated that the ER-3A insert earphone may sometimes be directly substituted, without recalibrating, for a TDH-39/MX-41AR earphone. However, most available data have not been reduced to a form suitable for establishing a revised estimate of the reference threshold levels. This article reports such a data analysis performed on the results of five recent studies. The mean data from the five studies are typically within 1 dB of the provisional reference threshold SPLs given by the ER-3A manufacturer for calibration in a (HA-1) 2-cc coupler. After converting the mean data to equivalent Zwislocki-coupler-type ear simulator SPLs at each of the reported audiometric frequencies (125, 250, 500, 1000, 2000, 3000, 4000, 6000, and 8000 Hz), agreement within 1.5 dB was seen with the revised estimate of minimum audible pressures given by Killion [J. Acoust. Soc. Am. 63, 1501-1508 (1978)]. Either the manufacturer's provisional SPLs or the average results from this study may be used with little noticeable difference for most purposes.
Auditory Threshold↗
Is it necessary to measure hearing protector attenuation at 3.15 and 6.3 kHz?
The real-ear attenuation data for 81 different hearing protectors were analyzed with respect to the errors that would arise if, instead of averaging the 1/3-octave-band results at 3.15 and 4 kHz and 6.3 and 8 kHz, respectively, the octave-band attenuation at 4 and 8 kHz was estimated from only the 1/3-octave-band data at those two frequencies. Errors as large as 3-4 dB were found to occur in rare instances, but more typically were in the range of 0.5-1.5 dB. However, in terms of computation of an overall noise reduction rating such as the NRR, the effect of excluding the 3.15- and 6.3-kHz data led to errors that averaged only 0.1 dB and never exceeded 0.3 dB, except in one instance, where the error was 0.6 dB. It was concluded that there is little value in measuring real-ear attenuation in a diffuse sound field at the frequencies of 3.15 and 6.3 kHz for applications in which hearing protector attenuation data are normally utilized.
Acoustic Stimulation↗
Application of the articulation index to the speech recognition of normal and impaired listeners wearing hearing protection.
The present study examined the application of the articulation index (AI) as a predictor of the speech-recognition performance of normal and hearing-impaired listeners with and without hearing protection. The speech-recognition scores of 12 normal and 12 hearing-impaired subjects were measured for a wide range of conditions designed to be representative of those in the workplace. Conditions included testing in quiet, in two types of background noise (white versus speech spectrum), at three signal-to-noise ratios (+ 5, 0, - 5 dB), and in three conditions of protection (unprotected, earplugs, earmuffs). The mean results for all 21 listening conditions and both groups of subjects were accurately described by the AI. Moreover, a single transfer-function relating performance to the AI could describe all the data from both groups.
Acoustic Stimulation↗
Risk factors for hearing loss at different frequencies in a population of 47,388 noise-exposed workers.
Weighted regression analysis was applied to determine the dependence of the hearing thresholds of 47,388 noise-exposed workers on age, sex, noise immission level, ear disease, head injury, tinnitus, hearing protector usage, and audiometric frequency in the range from 0.5 to 6 kHz. It could be shown that the hearing thresholds at any frequency are dominated by the age of the worker and that women, after equivalent exposure conditions, hear better than men. The relative effects of sex, noise immission level, ear diseases, tinnitus, and hearing protector usage are related to the audiometric frequency. Users of hearing protectors at the last audiometric investigation hear worse than nonusers. Hearing protector usage is strongly related with the hearing threshold in the low-frequency range. The noise immission level does not noticeably affect the hearing threshold below 3 kHz. The most important frequency of the noise immission level is as expected 4 kHz. For 4 kHz, it was shown that the variables age, noise immission level, tinnitus, head injuries, and ear diseases act in a good approximation additively on the pure-tone hearing threshold.
Adolescent↗