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PubMed1998

Effects of active noise reduction on noise levels at the tympanic membrane.

BACKGROUND: Active noise reduction (ANR) is an electronic system that works by continuous sampling of noise inside the earshell of the headset with a small microphone. This signal is inverted in phase through the headset speaker, thus reducing noise levels by destructive interference of the acoustic field. The system provides good low-frequency noise attenuation, but aircrew differ in their subjective opinion of ANR. The present study is an attempt to provide an objective assessment of the effect of ANR on noise levels at the tympanic membrane. METHODS: There were 7 subjects with normal ears who were placed in an environment of recorded noise from a BO-105 helicopter. A microphone probe was inserted to within 5 mm of the tympanic membrane of each subject's right ear. Noise levels in the ear were measured without a headset and with two different ANR headsets. Measurements were performed with and without the ANR system on, and with and without white noise through the headset communication system. The white noise was used to simulate aircraft communication noise. RESULTS: The two headsets tested had differing levels of passive and active attenuation. The ANR system produced a substantial low-frequency attenuation. However, noise levels in the mid frequencies increased somewhat when the ANR system was switched on. This effect was augmented when white noise in the communications system was introduced, particularly for one of the two headsets. Low-frequency noise attenuation of ANR systems is substantial, but an increased mid- and high-frequency noise level caused by the ANR may affect both communication and overall noise levels. Our data provide advice on what factors should be taken into account when ANR is evaluated for use in an aviation operational environment.

Aerospace Medicine↗
PubMed1988

Noise annoyance with regard to neurophysiological sensitivity, subjective noise sensitivity and personality variables.

To evaluate the relation between annoyance to environmental noise, general neurophysiological sensitivity, subjective noise sensitivity and other individual characteristics, experiments were undertaken in which 93 subjects assessed their subjective annoyance after exposure to noise under laboratory conditions. Evaluations were made of the discomfort threshold for pulsating sound, the light discomfort, and heat and cold discomfort. The heart rate and discomfort after exposure to a series of impulse noises was also determined. Subjective noise sensitivity, attitudes to noise, mood and personality characteristics of the subjects were evaluated using questionnaires. The results show that the annoyance after exposure to noise was not closely related to the general neurophysiological sensitivity, measured as discomfort threshold for noise, heat, cold and light; or to the heart rate reaction or discomfort after exposure to impulse noise. The annoyance was highly correlated with subjectively reported noise sensitivity and with the attitude to noise. There was also a relationship with neuroticism, measured with the EPI scale. It is suggested that the subjective noise sensitivity, attitude and neuroticism for the definition of noise sensitivity be defined in future studies of long term effects of noise exposure.

Adolescent↗
PubMedDate not supplied

Industrial noise exposure, noise annoyance, and serum lipid levels in blue-collar workers--the CORDIS Study.

Chronic noise exposure may constitute a risk factor for cardiovascular disease, but the exact mechanism is unclear. The authors studied the association between industrial noise exposure, noise annoyance, and serum lipid/lipoprotein levels in male (n = 1,455) and female (n = 624) blue-collar workers. The authors found that young men (i.e., < or = 44 y of age) exposed to high noise levels (> or = 80 dB[A]) had higher total levels of cholesterol (p = .023) and triglycerides (p = .001), as well as a higher cholesterol ratio (p = .038), than men exposed to low noise levels, even after controlling for confounding variables. In women or in older (> 45 y) men, noise did not affect serum lipid/lipoprotein levels. The authors found no interaction between noise exposure level and noise annoyance (except for high-density lipoprotein in women). However, noise annoyance covaried independently with total cholesterol (p = .022) and high-density lipoprotein (p = .0039) levels in young men and with total cholesterol (p = .035), triglyceride (p = .035), and high-density lipoprotein levels in women (under high noise exposure conditions)(p = .048) levels in women. Noise annoyance and noise exposure levels had an additive effect on cholesterol levels. Young men who scored high on both variables had a 15-mg/dl higher mean cholesterol level (95 % confidence interval [CI] = 7.2, 22.8; p = .0003) than those who scored low on both variables; in women, the corresponding difference was 23 mg/dl (95% CI = 1.5, 42.9; p = .019). The authors concluded that the examination of serum lipid/lipoprotein levels may be useful in studies of the health effects of noise, and particular attention should be paid to noise-annoyed individuals.

Adult↗
PubMed2003

Noise sensitivity and reactions to noise and other environmental conditions.

This article integrates findings from the literature and new results regarding noise sensitivity. The new results are based on analyses of 28 combined datasets (N = 23,038), and separate analyses of a large aircraft noise study (N = 10,939). Three topics regarding noise sensitivity are discussed, namely, its relationship with noise exposure, its working mechanism, and the scope of its influence. (1) A previous review found that noise sensitivity has no relationship with noise exposure. The current analyses give consistent results, and show that there is at most a very weak positive relationship. (2) It was observed earlier that noise sensitivity alters the effect of noise exposure on noise annoyance, and does not (only) have an additive effect. The current analyses confirm this, and show that the relation of the annoyance score with the noise exposure is relatively flat for nonsensitives while it is steeper for sensitives. (3) Previous studies showed that noise sensitivity also influences reactions other than noise annoyance. The current analyses of the aircraft noise study extend these results, but also indicate that noise sensitivity has relatively little influence on reactions to nonenvironmental conditions.

Aircraft↗
PubMed2004

The role of noise sensitivity in the noise-response relation: a comparison of three international airport studies.

In order to examine the role of noise sensitivity in response to environmental noise, this paper presents detailed comparisons of socio-acoustic studies conducted around international airports in Amsterdam, Sydney, and London. Earlier findings that noise sensitivity moderates the effect of noise on annoyance were examined to see if they could be replicated in each of the datasets, independent of the technique of measuring noise sensitivity. The relation between exposure to aircraft noise and noise annoyance was studied separately for groups of individuals with low, medium, and high noise sensitivity, with statistical adjustment for relevant confounders. Results support the previous findings that noise sensitivity is an independent predictor of annoyance and adds to the prediction of noise annoyance afforded by noise exposure level by up to 26% of explained variance. There is no evidence of a moderating effect, whereby the covariation between noise exposure level and annoyance is weak for people who score at the extreme high or low end of the sensitivity scale, and strong for people who score in the middle of the sensitivity scale. Generally, noise sensitivity appears to increase annoyance independently of the level of noise exposure after adjustment for relevant confounders. These findings were consistent across the three datasets.

Adolescent↗
PubMed1998

The masking-level difference in low-noise noise.

In experiment 1 NoSo and NoS pi thresholds for a 500-Hz pure tone were obtained in a low-fluctuation masking noise and a high-fluctuation masking noise for six normal-hearing listeners. The noise bandwidth was 10 Hz. In agreement with previous investigations, the NoSo thresholds were lower in low-fluctuation noise than in high-fluctuation noise. For three listeners, NoS pi thresholds were similar for the two types of noise, while for the other three listeners, Nos pi thresholds were higher for low-fluctuation noise than for high-fluctuation noise. In experiment 2, the masker was created by amplitude modulating a 500-Hz pure tone by a 0-10-Hz low-pass noise. The degree of masker fluctuation was controlled by adjusting the average modulation depth (100%, 63%, 40%, and 25%). The signal was a 10-Hz-wide noise centered on 500 Hz. Results were similar to those of experiment 1: for the NoSo conditions, signal detection improved with decreasing degree of fluctuation, and for NoS pi conditions, the results were subject dependent. For three listeners, NoS pi thresholds were again similar in the two types of noise, while for the other three listeners, NoS pi thresholds were again higher in low-fluctuation noise than in high-fluctuation noise. The results showed that a high degree of masker fluctuation sometimes facilitates NoS pi detection. It is possible that the binaural detection mechanism utilizes the relatively good signal-to-noise ratios that occur in the low power or "dip" regions of fluctuating masker waveforms.

Adult↗
PubMed2001

Speech recognition in noise for cochlear implantees with a two-microphone monaural adaptive noise reduction system.

OBJECTIVE: In this study the performance of a noise reduction strategy applied to cochlear implants is evaluated. The noise reduction strategy is based on a 2-channel adaptive filtering strategy using two microphones in a single behind-the-ear hearing aid. DESIGN: Four adult LAURA cochlear implant users (Peeters et al., 1993) took part in the experiments. The tests included identification of monosyllabic CVC (consonant-vowel-consonant) words and measurements of the speech reception threshold (SRT) of lists of numbers, in background noise presented at 90 degrees relative to the 0 degrees frontal direction of the speech. Percent correct phoneme scores for the CVC words at signal to noise ratios (SNRs) of -5, 0, and +5 dB in steady speech-weighted noise at 60 dB SPL and SRTs for numbers in speech-weighted steady and nonsteady ICRA noise were both obtained in conditions with and without the noise reduction pre-processing. Physical SNR improvements of the noise reduction system are evaluated as well, as a function of the direction of the noise source. RESULTS: Highly significant improvements in speech understanding, corresponding on average to an SNR improvement of about 10 dB, were observed with this 2-channel adaptive filtering noise reduction strategy using both types of speech-noise test materials. These perceptual evaluations agree with physical evaluations and simulations of this noise reduction strategy. Taken together, these data demonstrate that cochlear implantees may increase their speech intelligibility in noisy environments with the use of multimicrophone noise reduction systems.

Adult↗
PubMed1994

Noise exposure, noise annoyance, use of hearing protection devices and distress among blue-collar workers.

OBJECTIVES: This study tested the hypotheses that, in high noise levels [> or = 85 dB(A)], hearing protection devices are used largely by workers sensitive to noise, as reflected by reports of noise annoyance, and that the usage would reduce distress symptoms. METHODS: Data collected from 1587 healthy male blue-collar workers included noise exposure level, noise annoyance, use of hearing protection devices, distress symptoms (somatic complaints and poststress irritability), and possible confounding by age, education and ethnic origin. RESULTS: Multiple logistic regression results indicated that the use of hearing protection devices was related to noise exposure level [odds ratio (OR) 2.94, 95% confidence interval (95% CI) 2.58--3.30], but more so to high noise annoyance (OR 3.03, 95% CI 2.77--3.29), even after control for age, education, and ethnic origin. No interaction was found between noise level and noise annoyance. These findings highlight the contribution of noise annoyance to the use of hearing protection devices. Of the 42.6% of workers using hearing protection devices in the presence of high ambient noise, 60% were highly annoyed. Noise-annoyed workers also tended to wear hearing protection devices even in low noise levels. The use of hearing protection devices was associated with lower distress symptoms among the low and moderately annoyed workers, but among the highly annoyed workers the reverse was true. CONCLUSIONS: Thus, for the highly annoyed workers, the use of hearing protection devices was perhaps an additional source of stress. One immediate implication of this study is that future intervention procedures should focus on unannoyed workers who tend to use hearing protection devices less.

Adult↗
PubMedDate not supplied

ICRA noises: artificial noise signals with speech-like spectral and temporal properties for hearing instrument assessment. International Collegium for Rehabilitative Audiology.

Current standards involving technical specification of hearing aids provide limited possibilities for assessing the influence of the spectral and temporal characteristics of the input signal, and these characteristics have a significant effect on the output signal of many recent types of hearing aids. This is particularly true of digital hearing instruments, which typically include non-linear amplification in multiple channels. Furthermore, these instruments often incorporate additional non-linear functions such as "noise reduction" and "feedback cancellation". The output signal produced by a non-linear hearing instrument relates to the characteristics of the input signal in a complex manner. Therefore, the choice of input signal significantly influences the outcome of any acoustic or psychophysical assessment of a non-linear hearing instrument. For this reason, the International Collegium for Rehabilitative Audiology (ICRA) has introduced a collection of noise signals that can be used for hearing aid testing (including real-ear measurements) and psychophysical evaluation. This paper describes the design criteria, the realisation process, and the final selection of nine test signals on a CD. Also, the spectral and temporal characteristics of these signals are documented. The ICRA noises provide a well-specified set of speech-like noises with spectra shaped according to gender and vocal effort, and with different amounts of speech modulation simulating one or more speakers. These noises can be applied as well-specified background noise in psychophysical experiments. They can also serve as test signals for the evaluation of digital hearing aids with noise reduction. It is demonstrated that the ICRA noises show the effectiveness of the noise reduction schemes. Based on these initial measurements, some initial steps are proposed to develop a standard method of technical specification of noise reduction based on the modulation characteristics. For this purpose, the sensitivity of different noise reduction schemes is compared by measurements with ICRA noises with a varying ratio between unmodulated and modulated test signals: a modulated-unmodulated ratio. It can be anticipated that this information is important to understand the differences between the different implementations of noise reduction schemes in different hearing aid models and makes.

Acoustic Stimulation↗
PubMedDate not supplied

Stress effects of noise in a field experiment in comparison to reactions to short term noise exposure in the laboratory.

Reactions to noise-induced communication disturbance of 42 men during a seminar were investigated. Stress reactions with or without road traffic noise (Lm = 60 dBA) were compared. Traffic noise was played back via loudspeakers during one day in the seminar room. The following parameters were measured: Fatigue and mental tension by questionnaire; blood pressure and heart rate; excretion of adrenaline, noradrenaline and cAMP from the collected urine. The same subjects participated in a laboratory test where the blood pressure was measured during 5 minutes of rest and after 5 minutes of exposure to intermittent white noise (Lm=97 dBA). It was found that the noise in the field experiment caused psychological and physiological stress effects in half of the subjects. Increased mental tension was correlated to increases as well as decreases of the blood pressure. Systolic blood pressure reactions were stronger than the reactions of diastolic blood pressure. Noise sensitive subjects reacted stronger than the others. In the short-term laboratory test, systolic blood pressure increases were smaller than the diastolic increases. At the end of the 5 minutes noise exposure only the diastolic blood pressure increases were significant. There was no correlation between the blood pressure reactions in the two different noise exposure experiments. There existed a positive correlation between noise sensitivity and the systolic blood pressure increases during the seminar, whilst the correlation, between noise sensitivity and systolic blood pressure increases in the laboratory exposure, was negative. From these results we conclude that short-term noise exposure experiments do not provide information about the effects of long-term real life exposure to environmental noise. Potential health effects of chronic noise-induced disturbances of activities are discussed.

Adaptation, Physiological↗
PubMed2007

Extra-auditory effects of noise in laboratory animals: the relationship between noise and sleep.

Noise has both auditory and extra-auditory effects. Some of the most deleterious extra-auditory effects of noise are those leading to sleep disturbances. These disturbances seem to be related to both endogenous (physical parameters) and exogenous (sex, age) factors of noise. Despite correlative relations between noise level and awakenings, the scientific community has not reached consensus regarding a specific action of these factors on the different sleep stages. In animal research, 2 complementary main fields of research exist. One is focused on the positive modulation of sleep by repeated tone stimulation. The other concerns noise-related sleep disturbances. The few studies that have investigated noise-related sleep disturbances suggest the following conclusions. First, sleep disturbances are greater upon exposure to environmental noise, whose frequency spectrum is characterized by high and ultrasonic sounds, than white noise. Second, unpredictability and pattern of noise events are responsible for extractions from both SWS and PS. Third, chronic exposure to noise permanently reduces and fragments sleep. Finally, in chronic noise exposure, an inter-individual variability in SWS deficits is observed and correlated to a psychobiological profile related to an incapability to face stressful situations. Based on results from other research, acute noise-related sleep perturbations could result from an imbalance in the sleep-wake cycle in favor of arousing ascending systems. Chronic noise-related sleep disturbances may arise due to imbalance of the sleep-wake cycle and malfunctioning of the hypothalamo-pituitary-adrenal axis which may both contribute to the development of pathology.

Acoustic Stimulation↗
PubMed1986

Effects of interaural time delays of noise stimuli on low-frequency cells in the cat's inferior colliculus. I. Responses to wideband noise.

We examined the responses of low-frequency neurons in the central nucleus of the inferior colliculus (ICC) of the cat to interaurally delayed, wideband noise stimuli. The stimuli were pseudorandom noise signals that were generated digitally with a nominal bandwidth of 60-4,000 Hz. We also compared the responses to noise with those obtained from interaural phase differences of pure tones. We studied 144 neurons with characteristic frequencies below 2.5 kHz. Eighty-five percent (85%) of these were sensitive to changes in both interaural time differences (ITDs) of noise and interaural phase differences of pure tones, only 2% were sensitive to one stimulus but not the other, and the remainder were insensitive to both stimuli. For most cells the discharge rate was modulated in an approximately cyclic fashion by changes in ITDs of the wideband noise stimuli. The maximal spike counts often occurred near zero ITD, and there was considerable variability in the nature of the cycling, though it usually disappeared for ITDs greater than +/- 4,000 microseconds. The position of the central peak was usually (65%) within the physiologically relevant range of +/- 400 microseconds, and most (80%) occurred at positive ITDs, which corresponded to delays to the ipsilateral stimulus. In general, the shapes of the responses were not affected by changes in stimulus level above threshold. As long as identical noises were delivered to both ears, the responses were not sensitive to the particular noise stimulus used. When uncorrelated noises were delivered to the two ears, there was no sensitivity to ITDs. Composite curves were computed by linear summation of the responses to ITDs of pure tones at frequencies spaced at equal intervals throughout each cell's response area. The shapes of composite curves were similar to the responses of the same cell to ITDs of wideband noise stimuli. The positions of the central peaks of these two functions were highly correlated (r = 0.91, slope = 0.97). The values of characteristic delay and characteristic phase computed from the tonal responses were found to be good indicators of the shapes of the noise delay curves. Characteristic phases (CPs) near zero were associated with noise delay curves symmetric about the central peak, CPs near 0.5 cycles with those symmetric about the trough, while CPs between 0 and 0.5 or between 0.5 and 1.0 had noise delay curves that were asymmetric with a prominent trough to the left or right, respectively, of the central peak.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMedDate not supplied

Noise exposure, noise annoyance and their relation to psychological distress, accident and sickness absence among blue-collar workers--the Cordis Study.

This study examined the impact of chronic industrial noise exposure on psychological distress symptoms, accident involvement and sickness absence among male and female workers. It also examined whether workers expressing high noise annoyance were more adversely affected by it. Subjects were blue-collar workers, 1,680 males and 688 females, who participated in the Cordis Study. Noise exposure levels were: low [< 75 dB(A)], moderate [75-84 dB(A)], and high [> or = 85 dB(A)]. For males, noise exposure level affected job dissatisfaction and post-work irritability, while for females it also intensified somatic complaints, anxiety and depression. All the distress symptoms were higher for females. Further analysis showed that the significant increase of symptoms with noise exposure level was only for workers reporting high annoyance. Higher noise exposure levels were associated with increased accidents and sickness absence for both sexes. Noise-annoyed males had a significantly higher percentage of accidents when exposed to moderate noise levels and a marked increase in sick leave at high noise levels. Finally, the nonauditory effects studied here were already prevalent at moderate noise exposure levels, especially among noise-annoyed workers. This indicates the importance of reducing even moderately high levels of industrial noise not usually considered harmful to hearing.

Absenteeism↗
PubMed1993

Road traffic noise, noise sensitivity and psychological disorder.

The relationship between traffic noise exposure and psychological morbidity was assessed using the population-based Caerphilly Collaborative Survey of 2398 men from Caerphilly, South Wales, UK. The findings showed that annoyance to noise was strongly associated with traffic noise exposure levels. Men with noise sensitivity were more likely to be highly annoyed by noise exposure than men with less noise sensitivity. There was no direct association between noise exposure level and psychological morbidity until the results were stratified by noise sensitivity. This revealed a gradient of increasing psychological morbidity with increasing noise level in the lower two tertiles of noise sensitivity. No gradient was found in the highest tertile of noise sensitivity. The role of noise sensitivity is argued to be either an indicator of vulnerability to environmental stressors or a measure of overreporting.

Anxiety Disorders↗
PubMed2006

Enhancement of internal-noise coherence resonance by modulation of external noise in a circadian oscillator.

A circadian oscillator driven by external noise and internal noise has been studied by use of the chemical Langevin equation method. When the system is near a Hopf bifurcation and driven by internal noise only, it is found that the coherence resonance phenomenon can be induced by the internal noise. When the system is simultaneously driven by internal and external noise, it is found that external-noise coherence resonance can be suppressed by internal noise, while internal-noise coherence resonance can be enhanced by modulation of the external noise intensity in a certain range of noise intensity. Another interesting result is that the external noise can regulate the optimal system size when the internal-noise coherence resonance occurs.

Adaptation, Physiological↗
PubMed1999

Noise sensitivity as a factor influencing human reaction to noise.

Reaction (annoyance, dissatisfaction) to noise is itself an important health effect, as well as possibly contributing to other putative health effects of noise. Thus, factors such as noise sensitivity, which influence reaction, are of considerable importance. However, noise sensitivity is rarely clearly defined. This paper offers a formal definition of noise sensitivity, and reviews evidence relating to it. Noise sensitivity has been measured in various ways, but may be measured most directly by assessing reaction to many noise situations (other than those involving the noise source(s) which are the focus of the particular study). When noise sensitivity is measured in this way, factor analysis consistently reveals that noise sensitivity is not a unitary concept. Rather, two distinct factors appear: one related to loud noises (road traffic, lawn mower), and the other related to quieter noise situations which are nonetheless distracting (rustling papers at the movies, people talking while watching television). More research is needed to address the relationships between these factors, reaction and other health effects.

Journal Article↗
PubMed2000

Increased noise severity limits potentiation of noise induced hearing loss by carbon monoxide.

This study evaluates the influence of noise intensity and duration on auditory dysfunction due to simultaneous exposure to noise and carbon monoxide (CO). Previous studies have demonstrated that CO potentiates noise induced hearing loss (NIHL). It is not known whether auditory dysfunction due to combined exposure parallels impairment due to noise alone. Based on the 5 dB exchange rate between noise intensity and exposure doubling time, equivalent noise exposure conditions were used. Long Evans hooded rats were divided into groups that received noise alone (95, 100 and 105 dB SPL), and noise plus CO (1200 ppm), for durations of 4, 2 and 1 h, respectively. Controls were exposed to air or CO alone. Thresholds were evaluated 4 weeks later using an electrophysiological endpoint, the compound action potential threshold. Results demonstrate that the 5 dB exchange rate is not conserved under the conditions and subjects used. Moreover, dysfunction due to combined exposure did not parallel dysfunction due to noise alone. Further, although an increase in exposure duration results in increased auditory dysfunction, no further potentiation of NIHL by CO is observed. This suggests that at increasing noise severity, dysfunction due to combined exposure is limited by impairment due to noise alone.

Acoustic Stimulation↗
PubMed2001

[Study on the working noise in BYPC and the effects caused by working noise on the workers' vestibular and auditory function].

OBJECTIVE: In order to observe the kinds and intensity of the working noise of Yansan Petrochemical Co. and the effects caused by the working noise on the workers' vestibular and auditory function. METHOD: The intensity and frequency of the working noise were recorded by exactolnoisemeter in the workshop. One hundred and seventeen workers were tested in routine pure-tone tested method. The SPVN and ABR were tested within fifty-one workers of all. RESULT: The working noise of Yansan Petrochemical Co. belongs to the broad band and steady noise. The intensity of the working noise were during 85.7-104.0 dB(A) and the main frequency were during 1-8 kHz. About 59 percent workers who exposed to the working noise had hearing loss. The most hearing-loss were in the high frequency. The hearing-loss of speech frequency were slight. Workers who have more six years standing have obviously increased hearing-loss than the workers who have less five years standing. There were significant differences the ABR thresholds and wave-interval between the tested and controlled groups. The SPVN and CP were abnormal in more than 17.4 percent workers with hearing loss. CONCLUSION: The working noise of Yansan Petrochemical Co. belongs to the broad band and steady noise. Working noise can lead to workers' hearing loss of certain degrees who exposed in the noise for a long time. Obvious correlation was not defined between the hearing-loss and the abnormal vestibular response group.

Adult↗