Magnetic resonance imaging and tinnitus.
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Ear Protective Devices↗
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Effects of conductive hearing loss on temporal aspects of sound transmission through the ear.
Effects of conductive hearing loss on level and spectrum are well known. However, little is known about possible additional effects on temporal aspects of sound transmission. This study investigated effects of earplugs and middle ear effusions on amplitude and timing of cochlear microphonic (CM) responses in gerbils. Bilateral CM responses to pure tones (1-16 kHz) were monitored before and after (i). unilateral earplug insertion or (ii). injection of silicone oil, of various viscosities, into one middle ear. Earplugs produced flat hearing losses (mean 13 dB) and delayed CMs more at lower (mean 80 micros, 1-6 kHz) than at higher (20 micros, 8-16 kHz) frequencies. Effusions also produced flat hearing loss. On average, high viscosity effusions produced larger hearing losses (36 dB) than medium (25 dB) or low (20 dB) viscosity effusions. Low and medium viscosity effusions delayed responses to lower (mean 82 and 65 micros respectively, 1-6 kHz) more than to higher (mean 20 and 10 micros respectively, 8-16 kHz) frequencies. High viscosity effusions produced smaller delays across all frequencies (mean 31 micros, 1-16 kHz). In normal animals, CM responses were not delayed over a wide range of stimulus levels. Therefore, in addition to attenuation, conductive loss distorts acoustic temporal cues important for hearing.
Animals↗
The use of active noise control (ANC) to reduce acoustic noise generated during MRI scanning: some initial results.
MRI scanning generates high levels of acoustic noise that cannot only pose a safety hazard, but also impair communication between staff and patient. In this article we present active noise control (ANC) techniques that introduce antiphase noise to destructively interfere with the MRI noise and with the aim of producing a zone of quiet around the patient's ears. Using noise recorded from a 1.0 Tesla midfield MR scanner the acoustic noise generated by three standard MR imaging sequences was replayed to a real time two channel ANC system. The results obtained show a useful attenuation of low-frequency periodic acoustic noise components. Therefore, in combination with standard passive ear protection, this suggests that MR generated acoustic noise can be effectively attenuated at both low and high frequencies leading to improved patient comfort.
Acoustics↗
Blast injuries to the ear: an historical and literary review.
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Blast Injuries↗
Evaluation for waterproof ear protectors in swimmers.
The middle ear cavity is exposed and vulnerable to waterborne infection in patients with grommets, perforated tympanic membranes and after radical mastoidectomy. Patients suffering from chronic otitis externa and those receiving radiotherapy to the head and neck also have an increased susceptibility to such infections. Many advocate the use of waterproof ear protectors in such patients when swimming. The choice of a suitable ear protector is complicated as many are now available commercially. This study was therefore designed to evaluate the degree of protection afforded by seven different ear protectors in a group of six swimmers. A very sensitive, original method of water detection was devised incorporating a pH indicator strip. The results showed conclusively that cotton wool coated in paraffin jelly BPC was the most effective method of ear protection and was found to be comfortable and easy to use. Other methods, including custom-made silicone rubber plugs, were not adequate in sealing the external auditory canal and are considerably more expensive.
Adolescent↗
The Dansac mini cap: a new method of waterproof ear protection.
The best method of providing waterproof protection for susceptible ears remains a contentious issue. Many evaluations have concentrated on the efficacy of intraluminal plugs in normal or model ears. We describe a new method, using a jejunostomy shower cap (Dansac mini cap), which avoids intraluminal insertion. This method has proved useful in some patients who have failed to avoid repeated otorrhoea after water exposure despite using a wide range of intraluminal ear plugs. The shower caps are best avoided in children because of teasing.
Adolescent↗
Bone conduction errors at high frequencies: implications for clinical and medico-legal practice.
The magnitude and origin of audiometric air-bone gaps in the range 3 kHz to 8 kHz was investigated in 20 normal subjects. The average gap ranged from a minimum of about 3 dB at 3 kHz to a maximum of about 19 dB at 6 kHz. Approximately 5 dB of the gap at high frequencies is caused by excess air-radiated sound from the bone vibrator. A larger error appears to result from discrepancies between the air and bone conduction standards to which audiometers are calibrated. These errors may influence diagnosis and we recommend that bone conduction tests at frequencies greater than 4 kHz are avoided. These findings have implications for medico-legal work where small air-bone gaps have diagnostic significance.
Audiometry, Pure-Tone↗
Ear protection as a treatment for disruptive snoring: do ear plugs really work?
BACKGROUND: In the absence of surgical treatments with demonstrable long-term efficacy, conservative treatments for snoring remain appropriate. Only limited evidence evaluating the use of ear protection by partners has been published. METHODS: Eligible couples were invited to participate in a two-month trial, with each partner using custom-moulded ear plugs. Five questionnaires were completed by patients and their partners, at baseline and after two months: the snoring outcomes survey (SOS) or the spouse/bed partners survey (SBPS), the Epworth sleepiness scale (ESS), the general health questionnaire-12 (GHQ-12), the Nottingham health profile (NHP) and the Golombok-Rust inventory of marital status (GRIMS). RESULTS: After two months, there was a significant improvement in the SOS score for patients (p = 0.005), the SBPS score for partners (p = 0.001) and the ESS for partners (p = 0.004). CONCLUSIONS: For selected couples, ear plugs represent an effective short-term treatment for some of the social effects of disruptive snoring, as determined by the SOS, SBPS and ESS questionnaires.
Ear Protective Devices↗
Temporary threshold shift due to recreational firearm use.
OBJECTIVE: To assess whether a temporary threshold shift occurred after recreational firearm use. DESIGN: An observational study of 25 subjects using ear protection in an indoor rifle range. Hearing was evaluated before and after shooting five rounds with a 0.22 calibre rifle over 10 minutes. A threshold shift of 5 dB was found to be statistically significant, while a shift of 10 dB was clinically significant. RESULTS: Twenty-four candidates had a statistically significant threshold shift, while 12 had a clinically significant threshold shift. Two subjects with previous industrial noise exposure had threshold shifts at more frequencies than other subjects. There was no significant preference for either ear. One subject showed no changes. CONCLUSION: This small study sheds some light on impulse noise behaviour in an indoor shooting range, but no definite conclusions can be drawn. The side of shooting did not influence threshold changes in either ear.
Adult↗
Tinnitus and hearing loss in hamsters (Mesocricetus auratus) exposed to loud sound.
Hamsters were trained to go left and right to sounds on their left and right sides, respectively. Silent trials were occasionally given in which no sound was presented. Hamsters exposed to a loud 2- or 10-kHz tone in 1 ear often shifted their responding on the silent trials to the side of the exposed ear, suggesting that they perceived a sound in that ear (i.e., tinnitus). The degree of tinnitus was related to the degree of the accompanying hearing loss (estimated by the auditory brainstem response). However, a conductive hearing loss (plugging 1 ear) did not cause a hamster to test positive for tinnitus. Tinnitus could be demonstrated within minutes following tone exposure, indicating an immediate onset, as occurs in humans.
Acoustic Stimulation↗
[Measurement of noise protection in functional magnetic resonance imaging].
BACKGROUND: Functional magnetic resonance imaging (fMRI) can detect changes in oxygen saturation of the brain. Fast changing high gradient fields are necessary which produce high levels of noise. In studies of the auditory cortex, auditory stimuli have to be perceived and discriminated against the noise level of the activated tomograph. MATERIAL AND METHODS: The generated frequency bands and their intensities during fMRI with a Siemens Magnetom Vision, 1.5 T, EPI sequence were measured in the outer ear canal of a dummy head. Noise attenuation was evaluated with four different noise muffs (simple/inexpensive products, quality product, specialized fMRI muffs). RESULTS: Without protection, peak noise levels reached up to 111 dB(A) near 1000 Hz in the dummy ear canal. Major noise attenuation was only found at higher frequencies (4000 Hz by about 25 dB; 8000 Hz by about 35 dB) with the quality product and the specialized fMRI muffs. CONCLUSION: Only quality noise products can sufficiently protect patients from high sound pressure levels of tomograph noise. If in the future higher gradient fields are applied at faster slew rates, acoustic stimuli can safely be applied only in combination with increased hearing protection systems in order to minimize the risk of noise trauma.
Ear Protective Devices↗
[Protection for noise-induced hearing loss using active hearing protection systems].
Though noise induced hearing loss is no longer the most frequent occupational disease in the Federal Republic of Germany, the environmental pollution by the product "noise" in our technical and industrialized world has not been reduced. On the contrary, the situation is worsened by the rising influence of leisure noise. To avoid occupational hearing loss, the "Noise Injury Prevention Code" issued by the insurers would demand wearing personal ear protection, e.g. ear plugs, if ambient noise levels are above 85 dB(A). But there are working places in which such equipment would have precisely the adverse effect, because one of the reasons for possible damage to hearing is radio communication. In military aircraft cockpits for example noise exposure measurements showed ambient noise levels above 90 dB(A) during regular flight service nearly all the time. To be able to understand radio traffic in spite of the noisy environment, the headphone volume must be raised above the noise of the engines. The use of ear plugs can only be of limited value. Whereas pilots with normal hearing show only little impairment of speech intelligibility, those with noise-induced hearing losses show substantial impairment that varies in proportion to their hearing loss. Communication abilities may be drastically reduced which may compromise the reliability of radio traffic. To avoid compromising air security one has to demand a noise protection system which allows to reduce ambient noise levels without disturbing speech intelligibility in the inevitable radio communication. Nowadays active noise cancelling (ANC) systems by electronic compensation in different ways provide effective protection against noise induced hearing loss.(ABSTRACT TRUNCATED AT 250 WORDS)
Acoustic Stimulation↗
[Electronic noise compensation for improving speech discrimination in airplane pilots].
Noise exposure measurements were performed in pilots of the Federal Navy during realistic flight situations. The ambient noise levels during regular flight service were maintained at levels nearly all the time above 90 dB. To avoid occupational hearing loss, the "Noise Injury Prevention Code" issued by the insurers would demand wearing personal ear protection, e.g. ear plugs. But such equipment in the aircraft cockpit would have precisely the opposite effect, because one of the reasons for possible damage to hearing is radio communication. To be able to understand radio traffic in spite of the noisy environment, headphone volume must be raised above the noise of the engines. The use of ear plugs can be of only limited value. Whereas pilots with normal hearing show only little impairment of speech intelligibility, those with noise-induced hearing loss show substantial impairment that varies in proportion to their hearing loss. Communication abilities may be drastically reduced which may compromise the reliability of radio traffic. Cockpit noise has its maximum intensity around 125 Hz and flight helmets and ear defenders are not very effective in low frequency ranges. Sennheiser electronic KG developed an active noise compensation circuit, which makes use of the "anti noise" principle. Here the outside noises picked up by two microphones integrated into the headset are processed electronically in such a way that they largely neutralise the original noise. It had to be made sure that the radio traffic signal was not also compensated and that the signal to noise ratio was clearly increased.(ABSTRACT TRUNCATED AT 250 WORDS)
Aircraft↗
Interpreting noise dosimeter results based on different noise standards.
Three types of noise dosimeters were exposed on workers during routine work in a synthetic rubber plant, two refineries, a petrochemical plant, a petroleum marketing terminal and an off-shore producing platform. The dosimeters represent different methods of noise integration.
Ear Protective Devices↗
Abrasive blasting protective practices study--field survey results.
A nationwide field survey of abrasive blasting practices revealed equipment deficiencies and lack of maintenance to be the rule, with workers exposed to extreme noise environments and above TLV quartz exposures.
Air Pollutants↗
User tests of ear defenders.
Ten different common muff-type ear defenders were tested by 50 potential users for comfort and ease of use. Results showed short-term (3 min) impressions to be a good predictor of long-term comfort; defenders were ranked for comfort and pointers are given for important design features. Only comfortable ear defenders will be worn properly.
Ear Protective Devices↗
Investigation of sound level conversion as a means of rating ear protector performance.
Sound level conversion, a single-number measure describing the noise reduction afforded by ear protectors, was calculated for 30 ear protectors in 615 industrial noise spectra. The results vindicate the utility of this measure for situations in which the noise hazard is characterised only by C- and A-weighted sound levels. A simple procedure for calculating SLC, accurate within +/- 1dB, is proposed. Minor adjustments of the calculation procedure enable wearer protection rates in the range 50% to 97% to be achieved.
Ear Protective Devices↗
Methods of measuring and rating hearing protector performance.
This paper reviews various methods that have been used to measure and rate the performance characteristics of hearing protectors. Subjective and objective measurements methods will be discussed with respect to test method, environment and stimuli. A variety of methods for relating protector attenuation data to the requirements of a specific environment will be presented and discussed. The paper includes suggestions for use of this information with environmental data developed from octave band analysis or sound pressure level measured in dBA.
Ear Protective Devices↗