Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “NOISE”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 793 records · Page 44Linked to original sources
PubMed2006

Effect of noise on the morphology of the intestinal mucosa in laboratory rats.

To determine whether noise-induced stress disrupts the intestinal mucosa of laboratory rats, one group of 8 rats ("noise" rats) was subjected to 15 min of white noise (90 dB) daily for 3 wk. Another group ("quiet"rats) was housed for 3 wk in an acoustically similar room but with no additional noise. A 3rd group ("recovery" rats) was housed in the noise room for 3 wk and then in the quiet room for a further 3 wk. The ilea were fixed for microscopy. Villi adjacent to Peyer patches showed significantly more degranulated mast cells (mean+/-standard error of the mean, 3.95+/-0.80 versus 0.35+/-0.29, respectively) and eosinophils (mean+/-standard error of the mean, 9.46+/-0.44 versus 4.58+/-0.38) per villus section in noise rats than in quiet rats. Similar results were obtained with rooms reversed, to account for any differences in room characteristics. The mean width of villus laminar propria was significantly greater in noise rats than quiet rats, suggesting edema. In addition, mucosal epithelial cells of noise rats were often separated, sometimes detaching from the basement membrane, whereas those of quiet rats were intact. Behaviorally, noise rats exhibited significantly more grooming and rearing than quiet rats. Compared with noise rats, recovery rats showed no reduction in mast cell degranulation or mean width of villus lamina propria, but there were increased numbers of secreting goblet cells in villi adjacent to Peyer patches and some recovery of epithelial integrity.

Animal Welfare↗
PubMedDate not supplied

[Noise and office work].

BACKGROUND: The problem of the assessment of noise annoyance in the workplace has long been a topic of discussion. Several studies led to the definition of a set of descriptors suitable to describe noise in the workplace and its effects in terms of annoyance of the subjects exposed. OBJECTIVES: The aim of the study was to analyse the performance of different indices in terms of correlation with subjective sensation, taking into account those indices which combine both the intensity and the spectral quality of noise. METHOD: A noise survey was carried out in ten ofice buildings, covering 85 rooms. Objective measurements of environmental noise were made together with subjective evaluations collected through questionnaires. Subjective ratings were then averaged and correlated with objective parameters. Linear regression analyses were performed in order to assess the reliability of objective noise indices. RESULTS: The most important sources of noise were face-to-face and telephone conversations. All spectra had excess high frequency content. Regression analysis showed that under these conditions most noise indics provide a reliable prediction of subjective annoyance. However, the best performing parameter was the A-weighted equivalent sound pressure level followed by the Combined Noise Index which combines noise intensity and its spectral quality.

Acoustics↗
PubMed1991

Effects of noise on cognitive processes of individuals in a laboratory experiment.

The effects of noise on information processing in perceptual and memory tasks, as well as time reaction to perceptual stimuli, were investigated in a laboratory experiment. Performance and heart rate in Information Processing Test, Simple and Choice Reaction Time tests and Stroop's test were evaluated at three levels of noise (silence, 75 dBA, 95 dBA). Individual noise sensitivity and noise-induced temporary threshold shift (NITTS) were also assessed. The results show that neither noise nor individual noise sensitivity, or NITTS, as separate factors have an influence on information processing and time reaction to perceptual stimuli. However, noise effects simple reaction time in interaction with individual noise sensitivity, and information processing--within experimental session duration. Experimental session duration was the one separate factor affecting information processing. Noise as a separate factor does not have an influence on task performance, however, it affects heart rate. The higher increase of noise-induced temporary threshold shift, the smaller the number of heart beats/minute was found.

Adult↗
PubMed1977

Validation norms for speech discrimination scores of normal-hearing subjects in wide-band and in speech-spectrum noise at S/N 0 DB.

W-22 lists were given at 40 db re SRT with a Maico MA-24B audiometer and attachments to 20 normal-hearing adults in quiet and in combination with either wide-band or speech-spectrum noise at S/N = 0, monaurally by earphone and binaurally by loudspeaker(s). No systematic L-R differences were observed. DS in quiet by any condition was at or near 100%. Mean DS in noise by monaural earphone was 79.80 +/- 13.3 for wide-band noise and 54.7 +/- 12.7 for speech-spectrum noise. When speech and noise were from two different loudspeakers placed +/- 45 degrees from midline, DS was 90.8 +/- 9.5 for wide-band noise and 88.1 +/- 7.8 for speech-spectrum noise. When both speech and noise came from the same loudspeaker, DS was 79.10 +/- 10.3 for wide-band noise and 57.0 +/- 21.8 for speech-spectrum noise. These values are proposed as provisional norms for clinical facilities using these conditions and employing similar instrumentation.

Adult↗
PubMed1982

Intermittent-noise effects and hygienic standards.

Effects of variable equivalent intermittent noises on hearing acuity, peripheral vascular tonus and the latent period of motor responses were studied experimentally. Two-hour exposure to noise in the form of noise intervals of rectangular shape alternating with pause intervals at ratios of 20 :5, 20 :20, 20 :30, 10 :20 and 30 :60 seconds or to nonfluctuating noise was used. In all instances the equivalent level of noise was 80 dB(A). It was found that the degree of biological effect depended on the summary duration of the noise intervals in the total exposure period. A formula for correcting noise-level safety standards in the case of intermittent noises was proposed, viz: (formula; see text) where tau = summary duration of noise intervals and T = exposure time under evaluation. The possibility of using this relation also in evaluating situations where complementary to the equivalent level also the peak level of a given noise is subject to standardization is discussed.

Environmental Exposure↗
PubMed1998

Female voice communications in high level aircraft cockpit noises--part II: vocoder and automatic speech recognition systems.

BACKGROUND: The intelligibility of female and male speech is equivalent under most ordinary living conditions. However, due to small differences between their acoustic speech signals, called speech spectra, one can be more or less intelligible than the other in certain situations such as high levels of noise. Anecdotal information, supported by some empirical observations, suggests that some of the high intensity noise spectra of military aircraft cockpits may degrade the intelligibility of female speech more than that of male speech. METHODS: In an applied research study, the intelligibility of female and male speech was measured in several high level aircraft cockpit noise conditions experienced in military aviation. RESULTS: In Part I, (Nixon CW, et al. Aviat Space Environ Med 1998; 69:675-83) female speech intelligibility measured in the spectra and levels of aircraft cockpit noises and with noise-canceling microphones was lower than that of the male speech in all conditions. However, the differences were small and only those at some of the highest noise levels were significant. Although speech intelligibility of both genders was acceptable during normal cruise noises, improvements are required in most of the highest levels of noise created during maximum aircraft operating conditions. These results are discussed in a Part I technical report. This Part II report examines the intelligibility in the same aircraft cockpit noises of vocoded female and male speech and the accuracy with which female and male speech in some of the cockpit noises were understood by automatic speech recognition systems. The intelligibility of vocoded female speech was generally the same as that of vocoded male speech. No significant differences were measured between the recognition accuracy of male and female speech by the automatic speech recognition systems. The intelligibility of female and male speech was equivalent for these conditions.

Adult↗
PubMed2003

Monitoring and assessment of daily exposure of roadside workers to traffic noise levels in an Asian city: a case study of Bangkok streets.

Four noise monitoring sites were strategically established to evaluate average noise level and audiometric assessment at various traffic zones of Bangkok Metropolitan Region (BMR). During the monitoring period, noise levels were found to be 72.8-83.0 dBA during day time and 59.5-74.5 dBA during night time. The finding also indicated that traffic noise levels depend on distance from roadside, diurnal variation and character of the traffic and street configuration. Audiometric measurement of 4000 persons was carried by four major hospitals in Bangkok to study the relationship between traffic noise exposure of groups of people working in the streets and hearing loss. Four different categories of occupational people, i.e., drivers, street vendors, traffic officers and dwellers were selected and were further classified into age groups (16-25, 26-35, 36-45 and 46-55 years old) to monitor the traffic noise induced hearing loss throughout their everyday lives. The control group was deliberately chosen to screen out the effects of traffic noise. According to the audiometric investigation, it was revealed that hearing capacity of the daily noise exposure groups living in the three urban sites (Yaowarat Road, Din Daeng Road and Ratchaprarop Road) were noticeably poorer than those who were living in suburban site (Phahonyothin Road). It was noted that the mean hearing threshold level (HTL) of the 16-25 years old groups were found to have better hearing capacity than those older adults of 46-55 years old. In particular the mean HTL dropped at the frequency of 4000 Hz. Among the occupational population who were living in the urban monitoring sites, the driver groups were found to have the highest risk of traffic noise induced hearing loss.

Adolescent↗
PubMed1992

Frequency selectivity as a potential measure of noise damage susceptibility.

The notched-noise procedure of Patterson (1974, Journal of the Accoustical Society of America, 55, 802-809; 1976, Journal of the Acoustical Society of America, 59, 640-654) was employed in revealing changes in auditory frequency selectivity (FS) in noise-exposed industrial workers in manufacturing plants in which noise levels in the working environment exceeded 90 dB(A). With 4 kHz as the test frequency, both threshold and FS measures were applied to three groups of non-exposed young adults (total N = 61) for reference values and to workers in three different factories, some ('noise-exposed') working in noise levels over 90 dB(A) (total N = 222). In another study involving 185 workers only the FS test was repeated after a work session, and the results are reported on 31 who worked in high noise levels. Pre-work-shift data showed that when thresholds were better than 30-dB HL most FS values were 10 dB or more, while subjects with hearing threshold levels beyond that showed reduced FS. Two post-work-shift studies of 144 ears of the noise-exposed workers showed significant deleterious changes in both thresholds and FS but the relationships were different in the two studies. The findings indicate that the notched-noise test is sensitive to noise-induced auditory damage, even after a single work-shift. Attractive features of the procedure are that it reduces the need for a quiet test environment and that it can be more resistant to testee manipulation or threshold 'learning' effects, often seen in industrial audiometric testing.

Acoustics↗
PubMedDate not supplied

[An intervention policy for reducing noise pollution in urban areas].

The methodological methods for a reduction of the noise pollution in the urban areas, mainly, can be advised in 8 operative points: 1) reduction of the source's noise; 2) control of the traffic; 3) planning of the urban and regional development; 4) building's shelter against the noise; 5) compensation's and incentivation's interventions for the exposed people; 6) controls activity and restaining of the noise's sources; 7) scientific research; 8) health education. For executive motivations we must, necessarily, divide the intervention turned to a reduction of the noise's emissions caused by fixed source compared to the noise's emissions determined by motor or railway traffic (mobile sources). This operative criteria have been utilized recently (1988) from Italian Department of Ecology for a bill. The controls of fixed source are made by Public Health Services of U.S.L. (Local Sanitary Unit) assisted, in case, by multiarea country's districts. The regulations of traffic can be took in consideration, in short time, only in more simple problems, as the setting up of pedestrian island or the suspensions of the heavy traffic, etc. The traffic's regulation must care same general data: the halved of traffic's flow in same rilevation's point, involve a reduction of only 3 dBA of the sound pressure level previously measured; if the percentage of heavy traffic is higher than 10% of the traffic's flow, the first intervention must be the no thorough fare to heavy lorries. In general, then, the best way for the resolution of vehicular noise pollution is the noisy emission's control of the single vehicle, because only the regulation of traffic's flow doesn't suffice to realise a enough reduction of noise pollution. For the resolution of more complex problems is necessary a preliminary stage to study and to plan those before to can carry out a typology of intervention. This necessity is, of course, more expensive in time and money; in fact, the solution of the problem can be the building of a efficient subway network completed by car parks in the terminal stations. In alternation at this draft, we can pointed out, also, same compromise resolutions like the appoint areas to limited traffic in the town or the break of continuity of the bus-line in the town. The compensation or the incentivation to make defence works against noise is a very expensive way and, moreover, they don't solve the problem for all exposed people in a future.(ABSTRACT TRUNCATED AT 400 WORDS)

Automobiles↗
PubMed1986

Noise-induced hearing loss.

Hearing loss affects 30 million people in the United States; of these, 21 million are over the age of 65 years. This disorder may have several causes: heredity, noise, aging, and disease. Hearing loss from noise has been recognized for centuries but was generally ignored until some time after the Industrial Revolution. Hearing loss from occupational exposure to hazardous noise was identified as a compensable disability by the United States courts in 1948 to 1959. Development of noisy jet engines and supersonic aircraft created additional claims for personal and property damage in the 1950s and 1960s. These conditions led to legislation for noise control in the form of the Occupational Safety and Health Act of 1970 and the Noise Control Act of 1972. Protection of the noise-exposed employee was also an objective of the Hearing Conservation Act of 1971. Subsequent studies have confirmed the benefits of periodic hearing tests for workers exposed to hazardous noise and of otologic evaluation as part of the hearing conservation process. Research studies in laboratory animals, using scanning electron microscopical techniques, have demonstrated that damage to the inner ear and organ of hearing can occur even though subjective (conditioned) response to sound stimuli remains unaffected. Some investigators have employed an epidemiologic approach to identify risk factors and to develop profiles to susceptibility to noise-induced hearing loss. The need for joint involvement of workers and employers in the reduction and control of occupational noise hazards is evident.

Animals↗
PubMed1975

Potassium-ion conduction noise in squid axon membrane.

Spectral analysis (1-1000 Hz) of spontaneous fluctuations of potential and current in small areas of squid (Loligo pealei) axon shows two forms of noise: f-1 noise occurs in both excitable and inexcitable axons with an intensity which depends upon the driving force for potassium ions. The other noise has a spectral form corresponding to a relaxation process, i.e. its asymptotic behavior at low frequencies is constant, and at high frequencies it declines with a slope of -2. This latter noise occurs only in excitable axons and was identified in spectra by (1) its disappearance after reduction of K+ current by internal perfusion with solutions containing tetraethylammonium (TEA+), Cs+ or reduced [Ki+] and (2) its insensitivity to block of Na+ conduction and active transport. The transition frequency of relaxation spectra are also voltage and temperature dependent and relate to the kinetics of K+-conduction in the Hodgkin-Huxley formulation. These data strongly suggest that the relaxation noise component arises from the kinetic properties of K+ channels. The f-1 noise is attributed to restricted diffusion in conducting K+ channels and/or leakage pathways. In addition, an induced K+ conduction noise associated with the binding of TEA+ and triethyldecylammonium ion to membrane sites is described. Measurement of the induced noise may provide an alternative means of characterizing the kinetics of interaction of these molecules with the membrane and also suggests that these and other pharmacological agents may not be useful in identifying noise components related to the sodium conduction mechanism which, in these experiments, appears to be much lower in intensity than either the normal K conduction or induced noise components.

Animals↗
PubMed2002

Investigation into the origin of the noise of surface electrodes.

In the recording of biomedical signals, a significant noise component is introduced by the electrode. The magnitude of this noise is considerably higher than the equivalent thermal noise from the electrode impedance. As the noise in surface electrodes limits the resolution of biopotential recordings, it is important to understand its origin. It was found that the noise mainly originates in the electrolyte-skin interface and that it is highly dependent on the electrode gel used and the skin properties of the test subject. Depending on skin treatment, magnitudes between 1 and 20 microVrms were measured among subjects. When the metal-electrolyte interface was allowed time to stabilise, electrodes of different metals measured face to face all showed a negligibly small noise magnitude (< 1 microVrms). In pre-gelled electrodes, where the metal-electrolyte interface has stabilised, no difference in noise properties was found between Ag-AgCl electrodes and other metals when measured on the skin. In subjects at rest, the contribution of EMG signals to the total noise level was shown to be negligibly small compared with the noise contribution of the electrolyte-skin interface. The magnitude of the noise of electrodes appeared to be inversely proportional to the square root of the area of the electrode on the skin.

Electric Impedance↗
PubMed1973

Current levels of noise in an urban environment.

In 1961, the International Organization for Standardization prescribed upper tolerance limits for noise generated out-of-doors in residential districts. Between 1963 and 1970, vehicular traffic in the UK increased in volume by approximately 40%. This paper describes studies made throughout 1971 in which both peak and ambient noise-levels prevailing inside and outside buildings were measured. These levels were found greatly in excess of those regarded as tolerable ten years previously. Two methods for reducing noise-levels were considered. First, a barrier designed with the primary intention of reflecting rather than absorbing noise; secondly, a relatively simple form of double-glazing fitted to existing window frames. The barrier succeeded in reducing peak noise-levels but failed to influence ambients. The double-glazing attenuated both peak and ambient noise-levels significantly. Attention is drawn to the possibility of noise generated within buildings themselves becoming a source of discomfort for occupants and of annoyance to those outside. Noise-levels rising beyond 100 dB(A) were measured during evening business in the bar of a local hotel. A summary of data referring to noise-levels in the outdoor environment reveals that the upper tolerance limits prescribed by I S O are now being exceeded by 20 dB(A), or more, throughout 18 hours of the day. The findings are discussed in relation to the inevitable limits soon to be reached in adaptation of the human hearing mechanisms to increasing environment noise.

Journal Article↗
PubMed1992

On binocular unmasking of signals in noise: further tests of the summation hypothesis.

Observers detected the presence of Gabor signals in fields of two-dimensional broadband Gaussian noise encased by a frame of uniform noise. These images, displayed for 1 sec on a t.v. monitor, were seen through a simple-lens stereoscope. While the left and right eye were presented with the same view of the noise frame, the right-eye Gaussian noise field was right-shifted relative to the left-eye's by 20.3 min arc along the horizontal axis. Useful interocular cues concerning signal presence were not available in one set of trials (control condition), the right-eye signal being displaced by the same amount and direction as that of the noise. In another set of trials (experimental condition), such cues were made available by presenting the Gabor signals in exactly corresponding locations in the centres of the two frames. We tested the predictions of a model in terms of which the usefulness of binocular cues for the "unmasking" of the signal rests upon the characteristics of the summed monocular inputs, specifically the signal-to-noise ratio in the summed pattern. The two-dimensional power spectrum for the summed Gaussian noises shows "notches" at specific horizontal- and vertical-frequency intersections where the power density is at or close to zero. If the spectral power in the summed Gabor signal is concentrated at these locations in the experimental condition, the signal should be unmasked. Accordingly, the spatial frequencies and orientation of three Gabor patterns were chosen in such a way that the power density of the summed signals would fit in notches of the power spectrum of the summed noise, while it would overlap with a noise peak for a fourth Gabor signal. The findings were consistent with the summation hypothesis: binocular masking level differences of up to 18 dB were observed, but only for the three signals "falling" in the two-dimensional noise notches.

Adult↗
PubMed1989

How synaptic noise may affect cross-correlations.

The relationship between a postsynaptic potential (the 'test PSP') and the profile of the cross-correlation that it produces in a repetitively discharging mammalian motoneuron, with and without synaptic noise, has been explored by computer stimulation. In a noiseless motoneuron the cross-correlation profile represents the first derivative of PSP shape except where 'shadowing' occurs (Eqn. 1a-c). When synaptic noise is present the relationship changes. When the amplitude of spike-like 'noise PSPs' occurring at regular intervals reaches a critical value (Eqn. 2), all threshold crossings involve noise PSPs. Under these circumstances termed 'just maximally effective synaptic noise', the cross-correlation represents test PSP directly (Eqn. 3a). When the interval between noise PSPs is shortened the relationship reverts to the first differential (Eqn. 4a-c). If the amplitude of the noise PSPs is less than the critical value (Eqn. 5) the cross-correlation profile is represented in a complex way by a combination of the first derivative of the upper part and the direct representation of the lower part of the test PSP. The area of the cross-correlation peak above baseline provides the most reliable estimate of EPSP amplitude in a noiseless motoneuron (Eqn. 6a). This area may fall to half for the same triangular test EPSP in the presence of just maximally effective synaptic noise (Eqn. 7a). In general, the presence of synaptic noise leads to underestimation of EPSP amplitude. These general principles remain valid for physiological noise consisting of randomly occurring EPSPs and allow certain experimental findings in cat motoneurons to be understood.

Animals↗
PubMed2004

Effects of the noise level on induced motion.

Motion in a part of the field induces motion in an adjoining region. In this study, it was investigated how the noise level affects induced motion of a counterphase flickering (target) grating due to adjacent drifting (inducer) gratings. It was shown that at low noise levels, motion contrast occurred, and at high noise levels, motion assimilation occurred. When the noise level was randomly set for each trial, the adaptive change with the noise level was also observed. The result suggests that the adaptive change occurs for a short period. It was also found that noise for the target as well as noise for the inducers contributes to the effect of noise on motion induction. It suggests that the overall noise level is crucial for the effect. The study provided evidence that motion integration changes from a spatially band-pass operation to a low-pass operation as the signal-to-noise ratio (SNR) decreases.

Contrast Sensitivity↗
PubMed2005

What is the signal in noise?

Visual perception is limited by both the strength of the neural signals, and by the noise in the visual nervous system; however, little is known about what aspects of the input noise the human visual system is sensitive to, i.e., what is the signal in noise? In order to investigate this question we asked observers to discriminate differences in the strength of one-dimensional white noise. We measured their response consistency and classification images and compared the results with an ideal energy detector. Our results and modelling show that discrimination of noise is limited by the observer's template (i.e., the weighted combination of energy in each stimulus component) plus higher order nonlinearities (systematic noise), and by sources of random internal noise. We found that systematic noise is present only near detection threshold. Surprisingly, we found that the human template is "adaptive"-- its shape depends on the spatial frequency band of the noise-suggesting that sensitivity to spatial noise is not simply determined via passive filtering.

Discrimination, Psychological↗
PubMed1995

Molecular dynamics of alamethicin transmembrane channels from open-channel current noise analysis.

Conductance noise measurement of the open states of alamethicin transmembrane channels reveals excess noise attributable to cooperative low-frequency molecular dynamics that can generate fluctuations approximately 1 A rms in the effective channel pore radius. Single-channel currents through both persistent and nonpersistent channels with multiple conductance states formed by purified polypeptide alamethicin in artificial phospholipid bilayers isolated onto micropipettes with gigaohm seals were recorded using a voltage-clamp technique with low background noise (rms noise < 3 pA up to 20 kHz). Current noise power spectra between 100 Hz and 20 kHz of each open channel state showed little frequency dependence. Noise from undetected conductance state transitions was insignificant. Johnson and shot noises were evaluated. Current noise caused by electrolyte concentration fluctuation via diffusion was isolated by its dependence on buffer concentration. After removing these contributions, significant current noise remains in all persistent channel states and increases in higher conductance states. In nonpersistent channels, remaining noise occurs primarily in the lowest two states. These fluctuations of channel conductance are attributed to thermal oscillations of the channel molecular conformation and are modeled as a Langevin translational oscillation of alamethicin molecules moving radially from the channel pore, damped mostly by lipid bilayer viscosity.

Alamethicin↗