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PubMed2006

Effects of noise correlations on information encoding and decoding.

Response variability is often correlated across populations of neurons, and these noise correlations may play a role in information coding. In previous studies, this possibility has been examined from the encoding and decoding perspectives. Here we used d prime and related information measures to examine how studies of noise correlations from these two perspectives are related. We found that for a pair of neurons, the effect of noise correlations on information decoding can be zero when the effect of noise correlations on the information encoded obtains its largest positive or negative values. Furthermore, there can be no effect of noise correlations on the information encoded when it has an effect on information decoding. We also measured the effect of noise correlations on information encoding and decoding in simultaneously recorded neurons in the supplementary motor area to see how well d prime accounted for the information actually present in the neural responses and to see how noise correlations affected encoding and decoding in real data. These analyses showed that d prime provides an accurate measure of information encoding and decoding in our population of neurons. We also found that the effect of noise correlations on information encoding was somewhat larger than the effect of noise correlations on information decoding, but both were relatively small. Finally, as predicted theoretically, the effects of correlations were slightly greater for larger ensembles (3-8 neurons) than for pairs of neurons.

Action Potentials↗
PubMed2004

Impact of noise on retinal coding of visual signals.

Neural noise introduces uncertainty about the signals encoded in neural spike trains. Because of the uncertainty neurons can reliably transmit a limited amount of information. This amount is difficult to quantify for neurons that combine signals and noise in a complex manner, as many trials would be needed to estimate the joint probability distribution of stimulus and neural response accurately. The task is experimentally tractable, however, for neurons that combine signals with additive Gaussian noise. For such neurons, the joint probability distribution is well defined and information transmission rates can be computed from estimates of signal-to-noise ratio. Here we use power spectral analysis to specify the contributions of signal and noise to retinal coding of visual information. We show that in the spike trains of cat ganglion cells noise power is minimal and constant at temporal frequencies from 0.3 to 20 Hz and that it increases at higher frequencies to a plateau level that generally depends on stimulus contrast. We also show that trial-to-trial fluctuations in noise amplitude at different frequencies are uncorrelated and normally distributed. Although the contrast dependence indicates that noise at high temporal frequencies contributes nonlinearly to ganglion cell spike trains, cells in the primary visual cortex are not known to respond to stimulus modulations >20 Hz. Hence, noise in the retinal output would appear additive, white, and Gaussian from their perspective. This greatly simplifies analysis of information transmission from the eye to the primary visual cortex and perhaps other regions of the brain.

Action Potentials↗
PubMedDate not supplied

The effects of instructions, incentive, and feedback on a community problem: dormitory noise.

A reinforcement system utilizing instructions, modelling, feedback, and group reinforcement was employed in an attempt to reduce disruptive noise on three university residence halls. A fourth hall received the same treatment program without the reinforcement component. Noise scores were determined by recording the number of discrete noise occurrences over a criterion decibel level. On all four residential floors, noise scores during treatment conditions were lower than initial and final baseline levels. Additionally, periods of noise reduction corresponded to the changing criterion multiple-baseline and reversal designs utilized. Pre- and posttreatment questionnaire responses from the three reinforcement floors paralleled changes in objective noise data. At posttreatment, residents reported less noise disturbance of study and sleep and more control over the noise situation and floor problems in general. These results indicated that a comprehensive behavior-modification treatment package was effective in reducing disruptive noise in university residence halls. Difficulties in data collection and anomalies in the data are discussed. Future directions for field-based behavior-modification research are outlined.

Journal Article↗
PubMed1990

[Opening and closing mouth movements in subjects with TMJ noise. Three dimensional measurements on occlusal plane standard].

TMJ noise is one of the main symptom of TMJ disfunction. In this study the opening and closing movement of the mouth in subjects conscious of TMJ noise was observed three dimensionally. The occlusal plane was used as the standard for these three dimensional measurements. Changes resulting from the use of splints were also observed. The results were as follows: 1. Compared with normal subjects, the maximum value of fluctuation in subjects with TMJ noise for each particular measurement during opening and closing was distributed over a wide area. 2. The change in mandibular movement when the TMJ noise occurred was reproducible. 3. It was possible to divide the subjects with TMJ noise into three groups according to the particular splint used and the resulting noise changes. 4. In each group, the slant change on the occlusal plane was characteristically different when TMJ noise occurred before splints were fitted, and the changes after fitting particular splints were constant. 5. The above findings indicate that three dimensional measurements of slant changes on the occlusal plane when TMJ noise occurs may possibly be an important and useful index when examining subjects with TMJ noise.

Cephalometry↗
PubMed2002

Environmental Noise and Community in Hong Kong.

In order to find out the attitude of the community towards environmental noise, community surveys were conducted over the territory of Hong Kong through telephone sampling. Specific surveys were also carried out for areas previously affected by severe aircraft noise. Main observations on the community's response towards noise are that noise pollution was ranked the third among five selected social concerns (after "air pollution" and "security", and higher than "traffic jam" and "cleanliness"); about 60% of the respondents found the territory "noisy"; the most annoying noise source was "traffic noise"; 40% of people found the most annoying noise not tolerable and that most people affected by noise suffered from "distraction". Nonetheless, many did nothing (e.g. did not complain) against the noise and still preferred an open-window life style.

Journal Article↗
PubMed2001

Effect of long-term, low-level noise exposure on hearing thresholds, DPOAE and suppression of DPOAE in rats.

Loss of adaptability rather than loss of sensitivity may be one of the initial signs of auditory impairment following exposure to noise. One way to examine the adaptability of hearing in experimental investigation is to measure the magnitude of the suppression, exerted by the medial olivocochlear efferent system, on the ipsilateral otoacoustic emissions in response to contralateral sound stimulation. Thus, in order to test the hypothesis it was decided to measure hearing thresholds (HT), the cubic DPOAE and suppression of cubic DPOAE by contralateral wide band noise in rats exposed to long-term, low level noise (90 days of 90 dBlin 4-20 kHz wide band noise 4 hours/day, 5 days/week). Measurements of HT were performed by assessment of the ABR, elicited by tone-pips from the same probe assembly used in the measurements of DPOAE. The suppression of the cubic distortion product (CDP) was determined in ketamine/xylazine anaesthesia, allowing a stable response for a minimum of 20 min. Of the frequencies tested, the rats exposed to noise had an increase in HT at 12.8 kHz only (6.8 dB, P<0.05), while a reduction on the CDP was evident with f2 going from 9.2 kHz to the upper limit at 17.4 kHz. Further, the rats exposed to noise had little suppression of the CDP at low levels of contralateral noise (CN), but no difference from the control animals was seen as the CN noise level was increased. The measurement of DPOAE suppression did not reveal any effects of the low level noise exposure that was not paralleled also by shifts in hearing thresholds. The most sensitive assessment of the auditory changes in the study was the measurements of DPOAE, and further elaboration on the bandwidth and frequency distribution of the CN is necessary, before auditory changes in the high frequency range can be probably assessed.

Journal Article↗
PubMed2000

Characterising conditions that favour potentiation of noise induced hearing loss by chemical asphyxiants.

Hearing loss is the most common occupational disease in the United States with noise serving as the presumed causative agent in most instances; noise is identified as a prominent factor in approximately 10 million individuals in the United States with hearing impairments. Despite the characterisation of noise exposures that yield temporary and permanent threshold shifts and partial elucidation of mechanisms that are responsible for noise-induced hearing loss (NIHL), there remain significant knowledge gaps concerning factors causing NIHL. One such knowledge gap concerns potentiation of NIHL by simultaneous exposure to chemical agents. We have pursued investigation of the exposure conditions that facilitate the potentiation of NIHL by carbon monoxide. The selection of these specific agents is predicated upon the ubiquitous nature of exposure to chemical asphyxiants and a preliminary understanding of the mechanisms by which chemical asphyxiants disrupt hearing. Our data indicate that the potentiation of NIHL by carbon monoxide increases as a function of carbon monoxide concentration at levels of 500 ppm and above, but that the extent of potentiation shows a non-linear relationship to total noise energy with the greatest potentiation shown at moderate noise exposures that produce limited permanent threshold shifts. Further, the potentiation of NIHL by carbon monoxide appears to saturate as noise severity is increased such that at the most severe conditions used, the effects of carbon monoxide on NIHL are obscured totally by the noise effect. Finally, the data presented demonstrate that carbon monoxide is able to impair the recovery of NIHL that normally occurs when periods of silence are interspersed within noise exposure.

Journal Article↗
PubMed2000

The prevalence and type of social noise exposure in young adults in England.

There have been several recent reports on the potential risk to hearing from various types of social noise exposure. However, there are few population-based data to substantiate a case for concern. During the last 10-20 years use of personal cassette players (PCPs) has become very much more prevalent, and sound levels in public nightclubs and discotheques are reported to have increased. This study investigated the prevalence and types of significant social noise exposure in a representative population sample of 356 18-25 year olds in Nottingham. Subjects were interviewed in detail about all types of lifetime noise exposure. Noise measurements were also made for both nightclubs and PCPs. In the present sample, 18.8% of young adults had been exposed to significant noise from social activities, compared with 3.5% from occupational noise and 2.9% from gunfire noise. This indicates that social noise exposure has tripled since the early 1980s in the UK. Most of the present day exposure, measured in terms of sound energy, comes from nightclubs rather than PCPs. Moreover, 66% of subjects attending nightclubs or rock concerts reported temporary effects on their hearing or tinnitus. As will be reported in a later publication, any persistent effect of significant noise exposure on 18-25 year olds is difficult to show, however these data suggest that further work is indicated to study the possibility of sub-clinical damage, and also to consider the implications for employees of nightclubs.

Journal Article↗
PubMed2000

Effects of exposure to trichloroethylene and noise on hearing in rats.

Four groups of rats (n=8 per group) were exposed to either 3000 ppm trichloroethylene (TCE) alone or to 95 dB SPL noise alone or to the combination of TCE and noise or to control conditions. Exposure was carried out 18 hours/day, 5 days/week for 3 weeks. Exposure to TCE alone resulted in hearing loss at 4, 8, 16 and 20 kHz, but not at 24 and 32 kHz. Hearing loss due to exposure to noise alone occurred at frequencies of 8, 16 and 20 kHz. In general, combined exposure to TCE and noise resulted in larger auditory threshold changes than that produced by either TCE alone or noise alone when measured 1 and 2 weeks after the completion of exposure. For frequencies of 8, 16 and 20 kHz, hearing loss due to combined TCE-noise exposure was not larger than the algebraic sum of hearing loss due to exposure to TCE or noise alone. However, at a frequency of 4 kHz, hearing loss due to combined exposure was significantly larger than that produced by TCE exposure alone or noise alone, which itself had no effect at this frequency. These results suggest evidence of an interaction of combined exposure to TCE and noise at the lower edge of the range of frequencies affected.

Journal Article↗
PubMed1999

Exposure to Nocturnal Road Traffic Noise: Sleep Disturbance and its After Effects.

In this paper the disturbances to sleep caused by road traffic noise are reviewed in the light of the latest published findings. First, a short presentation is made of what noise is in general. Then an exposition is made of the different characteristics of road traffic noise and how it may be measured and rated with various descriptors. In general terms, the continuous exposure of people to road traffic noise leads to suffering various kinds of discomfort, thereby reducing the number of well-being elements. However, this conclusion is made more complex to attain when non-acoustical factors such as socio-economic situation, age and gender are taken into account. In broad terms, nocturnal road traffic activity leads to difficulties in falling asleep for people and to a reduction of their sleep quality. This, however, depends strongly on physical measures of noise like for instance the intermittency of loud single noise events, their level relative to that of the background noise and the frequency and time of their occurrence. Several studies have also confirmed the fact that mood, too, is strongly affected after spending a night with significant noise exposure. Other psychological and physiological functions affected by night-time exposure to road traffic noise, such as performance the following day and cardiovascular reactivity are also reviewed.

Journal Article↗
PubMed1999

Assessment of the effectiveness of aircraft noise regulation.

A fundamental goal of aircraft noise regulation is control of the prevalence of noise-induced annoyance in airport communities. A common regulatory strategy is to identify values of long-term, time-weighted average aircraft noise exposure that may not be exceeded in the vicinity of airports without certain consequences. Noise exposure per se is neither the sole cause nor a perfect predictor of the annoyance of aircraft noise, however. Regulatory limitation of noise levels to certain values of favored noise metrics may therefore provide the appearance, rather than the substance, of a solution to problems of community reaction to aircraft noise. Response bias, as identified by Green and Fidell (1991), is a factor that exerts about as much influence on the observed prevalence of annoyance in communities as cumulative noise exposure. The importance of formal consideration of response bias in assessments of the adequacy of regulatory enforcement levels is addressed.

Journal Article↗
PubMed1999

Personal and social variables as co-determinants of noise annoyance.

This paper starts with the fact that noise annoyance is partly due to acoustic factors, partly due to so-called moderating variables, i.e. personal and social aspects of the residents. Noise annoyance is considered to be the (long-term) negative evaluation of living conditions with respect to noise. This evaluation is not simply dependent on past disturbances, but on attitudes and expectations, too. The personal factors influencing the evaluation and described here are: Sensitivity to noise, fear of harm connected with the source, personal evaluation of the source, and coping capacity with respect to noise. The social factors described here are: General (social) evaluation of the source, trust or misfeasance with source authorities, history of noise exposure, and expectations of residents. For most of these variables, data from different community studies are used in order to illustrate the respective moderating effect on annoyance. In addition, some of the moderators are presented as possible tools in order to reduce noise annoyance. It is expected that a significant decrease in a negatively moderating variable is as effective in reducing noise annoyance, as is a significant decrease in noise level.

Journal Article↗
PubMed2005

Noise exposures of rail workers at a North American chemical facility.

BACKGROUND: Both continuous and impact noise exposures of rail yards and railways have been historically understudied. We summarize noise exposures to rail workers at a large chemical facility in North America. METHODS: Rail workers were surveyed over the course of three 12-hr shifts. Personal noise dosimeters were used to derive a 12-hr time-weighted average (L(AVG)), an 8-hr time-weighted average (L(TWA)), and a percent dose. Peak and maximum sound levels were also recorded during each sampling period. Six workers were sampled on three separate days for a total of 18 full-shift noise samples. RESULTS: Full-shift noise exposures were all below the Occupational Safety and Health Administration's (OSHA) permissible exposure limit (PEL) and action level for a 12-hr workday. Peak impact sound levels exceeded 140 dB in 17 of 18 samples (94%) with a mean peak sound level of 143.9 dB. Maximum continuous sound levels were greater than 115 dBA in 4 of 18 samples (22%) with a mean maximum sound level of 113.1 dBA. The source of peak impact sound levels was a daily exposure to a concussion caused by a sudden break in a freight airline. CONCLUSIONS: Rail workers at this facility are at risk of noise induced hearing loss from high impact noise exposures. Peak impact and maximum continuous sound levels can be attenuated through the use of hearing protection or by increasing distances from railroad noise sources.

Analysis of Variance↗
PubMed1985

Longitudinal study of growth status and airport noise exposure.

A study of children living adjacent to an international airport was conducted to learn whether noise exposure affected physical growth. Prenatal and postnatal noise exposures were estimated for each subject based on noise levels at their residences during jetplane takeoffs. Subjects' birthweights were standardized for sex and parity, and their postnatal heights and weights were standardized for sex and age (range 6-11 years). The difference between standardized birthweight score and postnatal height score, and between birthweight score and postnatal weight score, represent a change in growth status of a more or less permanent nature, respectively. After adjusting for confounding factors, children from the exposed community (n = 103) had a significantly smaller mean of status change by height (p less than 0.05), and a somewhat smaller mean of status change by weight (0.10 less than p less than 0.05) in comparison to children from an unexposed community (n = 94). A dose-response curve was then expected in the exposed community. However, in multiple regression analyses of the exposed children, noise exposure was not related to either change in growth status variable. This second result is inconsistent with the differences between communities and suggest that they are a result of factors other than noise exposure. We conclude that the moderate to severe noise levels of the areas surrounding most subjects' homes did not adversely affect postnatal growth. Further studies of noise and growth should concentrate observations on people exposed to even more severe noise levels than those experienced by most subjects in this study.

Aircraft↗
PubMedDate not supplied

Determination of gradient magnetic field-induced acoustic noise associated with the use of echo planar and three-dimensional, fast spin echo techniques.

The purpose of this study was to assess gradient magnetic-field-induced acoustic noise levels associated with the use of echo planar imaging (EPI) and three-dimensional fast spin echo (3D-FSE) pulse sequences. Acoustic noise measurements were obtained from two different high field-strength MR systems (1.5 T, Siemens and General Electric Co.) under ambient noise conditions and the use of EPI and 3D-FSE pulse sequences. Parameters were selected to produce "worst case" acoustic noise levels. Acoustic noise recordings were made at the entrance, the center, and at the exit of the magnet bores with a specially designed microphone that was unperturbed by electromagnetic fields. The highest ambient noise levels (A-weighted scale) were 67 dB (Siemens: the same values were recorded at the center and at the exit) and 78 dB (General Electric Co.; recorded at the exit). The highest acoustic noise levels recorded during activation of the gradient magnetic fields were 114 dB (Siemens) and 115 dB (General Electric Co.) and those occurred at the centers of the MR systems with the use of the EPI technique. Gradient magnetic fields associated with the use of EPI and 3D-FSE techniques produced acoustic noise levels that were within permissible levels recommended by federal guidelines.

Echo-Planar Imaging↗
PubMed1984

Industrial noise in residential areas: effects on residents.

In the surroundings of five industrial plants, noise immissions (industrial noise and non-industrial noise) were measured and residents asked by a questionnaire about the effects (annoyance and reactions) caused by industrial noise. The questionnaires of a total of 1498 (58%) residents could be analyzed. The Leq for the industrial noise ranges from 37 to 68 dB(A) in the daytime and from 37 to 59 dB(A) in the nighttime. Ten to 20% of the residents are already strongly annoyed at industrial noise Leq levels of 50 dB(A). The sensitivity to noise is higher in the evening and at night. Residents are disturbed mainly during their rest and recreation and often react by closing the windows. Limits for noise immissions caused by industrial plants in residential areas are proposed (Switzerland).

Attitude↗
PubMed1981

The effects of variable noise level on man with peak levels below 75 dB(A).

To estimate the effect of variable traffic noise levels by field study, six healthy students were exposed to such noise for 8 h in a building beside a highway. TTS increases and blood pressure changes were observed. A summary of the results is as follows: 1. Noise level slightly exceeded 70 dB(A) (Equivalent Sound Level, Leq). The ninety percent range of the changing noise level was within L50 + 10 dB(A). 2. The Temporary Threshold Shift (TTS) induced by variable noise increased slightly in this field experiment. In particular, regression of the logarithm of exposure time (min) to TTS at the "S" ward office, was statistically significant. Some subjects showed a rise of blood pressure due to noise exposure. 4. Even though noise level is below 75 dB(A), 8 h noise exposure induces TTS increase and elevation of blood pressure.

Auditory Fatigue↗
PubMed1994

Environmental and personal monitoring of exposure to urban noise and community response.

Noise exposure of a population sample living in a city in northern Italy (Genoa) was assessed by measuring the noise in the area as well as with personal sound detectors. Sampling was conducted during a standard day and covered a period of time spent out-of-doors, at work (service sector) and at home. Ambient noise at home and at work was assessed with sound-level meters, personal exposure levels were assessed with personal sound-level/dosimeters. Information regarding each environment was obtained with an interview including also a subjective judgement on traffic intensity and noise levels. The mean individual equivalent continuous sound level (Leq) of recorded noise was 74.5 dB(A) for 24 h and 63.9 dB(A) at night. A further distinction was made between noise exposure at home (Leq 74.4), work (Leq 74.0) and during city transfers (Leq 79.3). Leq values for individual hours, Leq daytime (Leq, d), Leq nighttime (Leq,n) and Leq day-night (Ldn) indices calculated in the different environments, i.e. at work, home and out-of-doors, are reported here. Individual noise levels have then been compared with environmental data and with subjective noise exposure judgement.

Environmental Monitoring↗