Equivalent Continuous A-weighted Sound Pressure Research Articles

Innovative bootstrap approach for the estimation of minimum measurement time interval in road traffic noise evaluation

Abstract It is observed that in order to characterize the environmental noise in a site, during diurnal reference time (6–22 h) or nocturnal reference time (22–6 h), relatively at preset time window, observation period, a single value of the equivalent continuous A-weighted sound pressure level L A,eq is used. This value is determined by integrating and averaging the squared A-weighted sound pressure of fluctuating noise during the measurement time interval, in which there are representative values of acoustic event pressure levels: so it is very important accurately to select the suitable integration time. Such matter are highly relevant to the area of measuring environmental noise and this paper aims to present a statistical method, for determining the minimum measurement time interval for an accurate estimation of L Aeq . The proposed algorithm, based on CPER bootstrap method, has been experimentally verified with real data obtained from road traffic noise measurement and it showed a very good stability. The methodology is suitable for upgrading the level meter firmware in order to have the real time information on the measurand uncertainty estimation and on the minimum measurement time interval.

Influences of combined traffic noise on anxiety in mice.

With the rapid development of traffic facilities in China, traffic noise pollution is increasingly prominent. This research aims to explore the influences of combined traffic noise on receptors' anxiety. Institute of cancer research mice were exposed to combined traffic noise (CTN) from highway and high-speed railway for 52days, whose day-night equivalent continuous A-weighted sound pressure level (Ldn) was 70dB(A). The impacts of CTN on anxiety were explored by behavior tests and monoamine neurotransmitter assays. The results were in depth discussed in comparison to two previous studies on the impacts of single high-speed railway noise (HSRN) and aircraft noise (AN), but data from the three studies were not merged and statistically compared. No significant differences were shown in the behavioral indicators and the monoamine levels between the experimental and control groups after CTN exposure, indicating no obvious impacts of 70dB(A) CTN on anxiety in mice were found in this study. When Ldn was approximately 70dB(A), CTN had less obvious impacts on anxiety than HSRN and AN, which is mainly related to that both the acoustical parameters of noise events [maximum noise level (LAmax), noise events duration, slope of rise, difference of LAmax from 1-min background equivalent continuous A-weighted sound pressure level] and modified day-night equivalent continuous R-weighted sound pressure level (considering animal auditory sensitivity to different sound frequencies and circadian rhythms) of CTN are smaller than those of HSRN and AN.

Effects of auditory and tactile warning on response to visual hazards under a noisy environment

A warning signal presented via a visual or an auditory cue might interfere with auditory or visual information inside and outside a vehicle. On the other hand, such interference would be certainly reduced if a tactile cue is used. Therefore, it is expected that tactile cues would be promising as warning signals, especially in a noisy environment. In order to determine the most suitable modality of cue (warning) to a visual hazard in noisy environments, auditory and tactile cues were examined in this study. The condition of stimulus onset asynchrony (SOA) was set to 0ms, 500ms, and 1000ms. Two types of noises were used: white noise and noise outside a vehicle recorded in a real-world driving environment. The noise level LAeq (equivalent continuous A-weighted sound pressure level) inside the experimental chamber of each type of noise was adjusted to approximately 60 dB (A), 70 dB (A), and 80 dB (A). As a result, it was verified that tactile warning was more effective than auditory warning. When the noise outside a vehicle from a real-driving environment was used as the noise inside the experimental chamber, the reaction time to the auditory warning was not affected by the noise level.

Statistical Analysis for Subjective and Objective Evaluations of Dental Drill Sounds.

The sound produced by a dental air turbine handpiece (dental drill) can markedly influence the sound environment in a dental clinic. Indeed, many patients report that the sound of a dental drill elicits an unpleasant feeling. Although several manufacturers have attempted to reduce the sound pressure levels produced by dental drills during idling based on ISO 14457, the sound emitted by such drills under active drilling conditions may negatively influence the dental clinic sound environment. The physical metrics related to the unpleasant impressions associated with dental drill sounds have not been determined. In the present study, psychological measurements of dental drill sounds were conducted with the aim of facilitating improvement of the sound environment at dental clinics. Specifically, we examined the impressions elicited by the sounds of 12 types of dental drills in idling and drilling conditions using a semantic differential. The analysis revealed that the impressions of dental drill sounds varied considerably between idling and drilling conditions and among the examined drills. This finding suggests that measuring the sound of a dental drill in idling conditions alone may be insufficient for evaluating the effects of the sound. We related the results of the psychological evaluations to those of measurements of the physical metrics of equivalent continuous A-weighted sound pressure levels (LAeq) and sharpness. Factor analysis indicated that impressions of the dental drill sounds consisted of two factors: “metallic and unpleasant” and “powerful”. LAeq had a strong relationship with “powerful impression”, calculated sharpness was positively related to “metallic impression”, and “unpleasant impression” was predicted by the combination of both LAeq and calculated sharpness. The present analyses indicate that, in addition to a reduction in sound pressure level, refining the frequency components of dental drill sounds is important for creating a comfortable sound environment in dental clinics.

保育園での子どもの遊び声に関する騒音測定調査

A survey was conducted to gather data for an assessment of the vocal noise level from children playing in nursery schools or other similar facilities. Ten nursery schools were surveyed; 5 locations in Setagaya Ward, Tokyo and 5 in Hachinohe, Aomori Prefecture. The surveys considered two cases: the noise levels while the children were playing in the yard, and those while they were playing inside. Measurements were taken over 10-minute intervals and the variables analyzed were equivalent continuous A-weighted sound pressure level ( called equivalent continuous noise level ), maximum noise level, percentile noise level, and frequency (1/1 and 1/3 octave bands). Additionally, at the first nursery school surveyed, a continuous measurement of the noise level was conducted for 24 hours to examine the conditions of measurements and the length of the analysis period. The noise level was found to be approximately 20 dB higher while the children were playing in the yard or in the pool than during other times of day, and that was about 30 dB louder than at night. In the nursery schools where the measurements were taken, the noise levels were also about 5 to 7 dB higher while the children were entering in the morning, which was not a dramatic difference. The equivalent continuous noise level measured 10 m from the center of a group of children playing in the nursery school yard was about 62 dB when there were 10 individuals and 74 dB when there were 100 individuals. However, it was possible for the noise to momentarily reach levels over 90 dB. The mean level of the vocal noise also increased by about 10 dB during music classes and when a microphone was being used. The frequency analysis of vocal noise from children indicated peaks of around 1000 Hz and 2000 Hz. There were linear decreases from these peaks at other frequencies. These values were higher than the pitches observed from conversations involving only adults. The effectiveness of a noise barrier installed within the nursery school grounds was estimated using the above results. Four cases were considered, where the height of the wall was varied from 2.0 m to 3.5 m. The wall was estimated to reduce the noise by 15 － 20 dB, which was considered to be sufficiently effective.

Individual daytime noise exposure in different microenvironments

BackgroundNumerous studies showed that chronic noise exposure modeled through noise mapping is associated with adverse health effects. However, knowledge about real individual noise exposure, emitted by several sources, is limited. ObjectivesTo explain the variation in individual daytime noise exposure regarding different microenvironments, activities and individual characteristics. Materials and methodsIn a repeated measures study in Augsburg, Germany (March 2007–December 2008), 109 individuals participated in 305 individual noise measurements with a mean duration of 5.5h. Whereabouts and activities were recorded in a diary. One-minute averages of A-weighted equivalent continuous sound pressure levels (Leq) were determined. We used mixed additive models to elucidate the variation of Leq by diary-based information, baseline characteristics and time-invariant variables like long-term noise exposure. ResultsOverall noise levels were highly variable (median: 64dB(A); range: 37–105dB(A)). Highest noise levels were measured in traffic during bicycling (69dB(A); 49–97dB(A)) and lowest while resting at home (54dB(A); 37–94dB(A)). Nearly all diary-based information as well as physical activity, sex and age-group had significant influences on individual noise. In an additional analysis restricted to times spent at the residences, long-term noise exposure did not improve the model fit. ConclusionsIndividual exposures to day-time noise were moderate to high and showed high variations in different microenvironments except when being in traffic. Individual noise levels were greatly determined by personal activities but also seemed to depend on environmental noise levels.

Simulation and Analysis of Noise Control Scheme for Hangzhou Cigarette Factory New Packing Workshop

Based on the noise test data of existing workshop, the noise of new packing workshop was studied. The effection of several noise control scheme was predicted by simulation and analysis method, and the control scheme five was chose finally ,by which average noise reduction was about 4.5dB,and 8h equivalent continuous A-weighted sound pressure level of the pick-up coil station and packaging machine station was 84.9dB and 83.2dB respectively, the working environment of the new workshop was effectively improved, and the investment was estimated.

Minimum measurement time interval to estimate a reliable sound pressure level of road traffic noise using two types of dynamic statistics

A new method to determine the minimum measurement time interval needed to obtain the equivalent continuous A-weighted sound pressure level with a designated reliability is presented. This method considers variations in the noise emission from passing vehicles. To verify the validity and availability, simulation experiments based on our dynamic model are examined under various traffic conditions. A statistic quantity, the mean time interval between two maximum sound pressure levels consecutively observed during the reference measurement time interval, is introduced in the experimental analysis. Additionally, the theoretical analysis includes another statistic quantity corresponding to the mean time interval, the mean recurrence time of the maximum sound pressure level, when the transition probability, rate of heavy vehicles, and probability distribution of vehicles passing the observation point during the reference measurement time interval are known.

Temporary Threshold Shifts from Exposures to Equal Equivalent Continuous A-weighted Sound Pressure Level

Temporary Threshold Shifts from Exposures to Equal Equivalent Continuous A-weighted Sound Pressure Level

モータ騒音影響を考慮した鉄道車両の環境影響評価

Objective. In order to evaluate the damage to inhabitants along the line resulting from conventional railway noise, it is necessary to evaluate influence by the noise quantitatively to consider the pattern of the noise in addition to the noise level. In this paper, damage by the railway motor noise is quantified taking driving pattern into consideration as well as noise level based on traffic noise evaluation method of LIME2.Results and Discussion. As a result of comparison of damage caused from noise by railway carriages equipped PMSM and IM through the life cycle, it is confirmed that 3dBA of equivalent continuous A-weighted sound pressure level based on actual measurement is corresponded to 56% reduction of health damage. In addition, as a result of integrated evaluation of plural environmental effects, the influence of damage by noise is 91% and 94% of total in the case of PMSM installed carriage and IM, respectively.Conclusions. In this paper, an evaluation model to quantify damage by railway noise is developed by reflecting the driving pattern of carriages based on LIME2. Using this model it is proved that the influence caused from noise is relatively high, therefore it is meaningful to involve the effect of noise to the total environmental analysis. In addition, in order to reduce the environmental impact, for the large influence in the operational stage, it is effective to control fuel consumption and the discharge of the environmentally load material in the operation stage.

Interior Noise Characteristics in Japanese, Korean and Chinese Subways

The aim of this study was to clarify the characteristics of interior noise in Japanese, Korean, and Chinese subways. The octave-band noise levels, A-weighted equivalent continuous sound pressure level (<TEX>$L_{Aeq}$</TEX>) and parameters extracted from interaural cross-correlation/autocorrelation functions (ACF/IACFs) were analyzed to evaluate the noise inside running train cars quantitatively and qualitatively. The average <TEX>$L_{Aeq}$</TEX> was 72-83 dBA. The IACF/ACF parameters of the noise showed variations in their values, suggesting they are affected by the characteristics of the trains running, wheel-rail interaction, and cross-section of the tunnels.

Survey of interior noise characteristics in various types of trains

The aim of this paper is to determine the effects of the wheel-rail friction, motor and tires on noise characteristics in a train car. The octave-band power levels, A-weighted equivalent continuous sound pressure level and parameters extracted from interaural cross-correlation/autocorrelation functions were analyzed to evaluate the noise inside running train cars quantitatively and qualitatively. The three types of noise caused by wheel-rail interaction are rolling, impact, and curve squeal noises. Impact noises had larger components at lower frequencies (< 1000Hz). Curve squeal noises had larger components at frequencies between 125 and 500Hz in both underground and surface trains and had dominant frequency components around 250 and 500Hz with stronger pitch in underground trains. High-speed trains had low-frequency centroids and high binaural coherence compared with normal-speed trains.

Autocorrelation function mechanism for pitch salience and cross-correlation function mechanism for sound localization revealed by magnetoencephalography

A model of primary sensations and spatial sensations is proposed by Ando (2001). The model of the auditory-brain system includes the autocorrelation function (ACF) and the interaural cross-correlation function (IACF) mechanisms. At present, environmental noises are evaluated by sound level such as equivalent continuous A-weighted sound pressure level (LAeq). However, we sometimes feel annoyed with sound with low sound level because of the quality. Sound quality can be characterized by factors obtained from ACF and IACF of sound. For example, pitch and pitch strength can be characterized by delay time and amplitude of the maximum peak of the ACF. Directional sensation can be characterized by delay time and amplitude of the maximum peak of the IACF. To verify the model, we investigated how ACF and IACF factors are coded in our human brain. The results indicated that delay time and amplitude of the maximum peak of the ACF and IACF are coded by the latency and strength of brain activity. In addition, we applied the model to analyze a Buddhist sutra chanted in temples. The results indicated that some characteristics of the sutra could be characterized by the ACF and IACF factors.

Field study on the influence of spatial and environmental characteristics on the evaluation of subjective loudness and acoustic comfort in underground shopping streets

A large-scale measurement and subjective survey was undertaken in five underground shopping streets to determine the influence of spatial and environmental characteristics on users’ subjective loudness and acoustic comfort. The analysis on the spatial characteristics shows that the subjective loudness is higher in “street type” than in “square type” underground shopping streets when the equivalent continuous A-weighted sound pressure level (LAeq) is relatively high (75dBA). Acoustic comfort is higher in “square type” than in “street type” underground shopping streets where LAeq is relatively low (55dBA). Considering spatial functions, it is found that acoustic comfort is higher in a dining area than in a shopping area. In terms of environmental characteristics where air temperature, relative humidity, luminance and visual aspect were considered, the subjective loudness is influenced by humidity and luminance, with correlation coefficients of 0.10–0.30. The evaluation of acoustic comfort is influenced by air temperature, humidity, and luminance, with correlation coefficients of 0.10–0.40. There are significant correlations between the evaluation of environmental factors and subjective loudness, as well as, acoustic comfort. The correlation coefficients are 0.10–0.50. Moreover, respondents’ attitude to sound environment could influence their evaluation of subjective loudness and acoustic comfort.

Individual Daytime Noise Exposure during Routine Activities and Heart Rate Variability in Adults: A Repeated Measures Study

Background: Epidemiological studies have demonstrated associations between noise exposure and cardiovascular events. However, there have been few studies of possible underlying mechanisms.Objectives: We examined the association between individual daytime noise exposure and heart rate variability (HRV).Methods: In a prospective panel study in Augsburg, Germany (March 2007–December 2008), 110 individuals participated in 326 electrocardiogram recordings with a mean duration of 6 hr. Five-minute averages of heart rate (HR) and HRV parameters were determined. Individual noise exposure was measured as A-weighted equivalent continuous sound pressure levels (Leq). Effects were estimated using additive mixed models adjusted for long- and short-term time trends and physical activity. Due to nonlinear exposure–response functions, we performed piecewise linear analyses with a cut-off point at 65 dB(A).Results: Concurrent increases of 5dB(A) in Leq < 65dB(A) were associated with increases in HR (percent change of mean value: 1.48%; 95% CI: 1.37, 1.60%) and the ratio of low-frequency (LF) to high-frequency (HF) power (4.89%; 95% CI: 3.48, 6.32%), and with decreases in LF (–3.77%; 95% CI: –5.49, –2.02%) and HF (–8.56%; 95% CI: –10.31, –6.78%) power. Standard deviation of normal-to-normal intervals (SDNN) was positively associated with concurrent noise < 65dB(A) (5.74%; 95% CI: 5.13, 6.36) but negatively associated with noise lagged by 5–15 min (–0.53% to –0.69%). Associations with cardiac function were less pronounced for noise ≥ 65dB(A), with some in opposite directions from associations with noise < 65dB(A). Concurrent associations were modified by sex and age.Conclusions: Individual daytime noise exposure was associated with immediate changes in HRV, suggesting a possible mechanism linking noise to cardiovascular risk. Noise at lower levels may have health consequences beyond those resulting from “fight-or-flight” responses to high levels of noise.

Behavioral and plasma monoamine responses to high-speed railway noise stress in mice

Studies have reported that railway noise causes stress responses. To evaluate the effects of high-speed railway (HSR) noise on behaviors and plasma monoamines. Institute of cancer research mice were exposed to previously recorded HSR noise for 53 days. The noise was arranged according to the HSR's 24-h traffic number and adjusted to a day-night equivalent continuous A-weighted sound pressure level (Ldn ) of 70 dB (A). The open field test (OFT) and the light/dark box test were applied to observe mice behaviors. High performance liquid chromatography-fluorimetric detection was performed to determine the concentrations of plasma norepinephrine (NE), dopamine (DA), serotonin (5-hydroxytryptamine, 5-HT). Data were analyzed by two-way analysis of variance using SPSS 16.0. After 53 days of noise exposure, center time and the frequency of line crossing of the exposed mice decreased significantly in the OFT compared with the control group. Meanwhile, transitions and the time spent in the lit compartment of the exposed group decreased significantly in the light/dark box test. After 40 days of HSR noise exposure, the concentrations of plasma DA of the exposed group were significantly higher than those of the control group, while the plasma NE and 5-HT concentrations showed no significant difference between the two groups. The behavioral tests indicate that 70 dB (A) HSR noise can result in anxiety-like behaviors in mice. The physiological results show that plasma DA is more sensitive to HSR noise compared with NE and 5-HT.

Assessment of Indoor Environmental Quality in Open-Plan Offices

This study aims to analyze the factors of indoor environment on occupants’ health and comfort by post-occupancy evaluation (POE) and to accumulate the fundamental data of occupants’ behaviour in relation to indoor environment, in an effort to ascertain the optimal building energy management system (BEMS). For this purpose, indoor temperature, relative humidity, vertical temperature distribution, air velocity, predicted mean vote (PMV), radiant temperature, outdoor temperature, and humidity were measured for evaluating thermal environment for nearly 2 years. Indoor air contaminants, such as PM10, CO2, formaldehyde, and volatile organic compounds (VOCs) were measured in the building and at outdoor locations. Working plane illuminance, window luminance, and the equivalent continuous a-weighted sound pressure level (Leq) were also monitored. In addition, the occupants in the intelligent office building were surveyed regarding the indoor environmental quality via the intranet. Results showed that all indoor environmental factors satisfied the recommendation, except the indoor relative humidity and PMV. The physical factors of thermal environment had been stable since two months after it was built. However, it should be necessary to improve the sound privacy caused by low background noise, seasonal air-conditioning for appropriate humidity, air freshness, and Video Display Terminal (VDT) glare in order to reduce the level of occupants’ annoyance.

Effects of high-speed railway noise on the synaptic ultrastructure and phosphorylated-CaMKII expression in the central nervous system of SD rats

To investigate the toxic effects of high-speed railway noise on learning and memory function, Sprague-Dawley (SD) rats were exposed to high-speed railway noise for 90 days. The noise was recorded from an actual environment and adjusted to a day–night equivalent continuous A-weighted sound pressure level (Ldn) of 70dB(A). Transmission electron microscopy (TEM) and Western blot analysis were used to observe the synaptic ultrastructure and detect the level of phosphorylated-Ca2+/calmodulin-dependent protein kinase II (p-CaMKII), respectively, in the hippocampus, temporal lobe and amygdala. Compared with the sham control group, the results of the TEM showed that the width of the noise model group's synaptic cleft increased markedly in the hippocampus, amygdala (P<0.05) and temporal lobe (P<0.01); the thickness of postsynaptic density (PSD) decreased significantly (P<0.01). The results of the TEM suggest that the synaptic plasticity of structure and function were abnormal and that this abnormality resulted in a reduction in synaptic transmission efficiency. This reduction may have led to dysfunctions in learning and memory. Additionally, the Western blot analyses revealed that the level of p-CaMKII decreased significantly in the temporal lobe of the noise model group compared with the sham control group (P<0.05). The results of the Western blot analysis indicate a reduction in synaptic transmission efficiency, which resulted in impairments in learning and memory function in the temporal lobe. Both of the above conclusions are consistent with each other.

Development of long-term data acquisition system of noise exposure and personal behavior for analysis of health risk: Preliminary studies

To investigate relationship between individual noise exposure and the effect on health, firstly we have designed a measuring equipment because commercially-available noise exposure meter adopts the averaging times of a few minutes that are longer for our purpose. Requirements of the equipment we focus on are to measure (1) intermittent characteristic of noise that include the maximum level, the number of event, and level difference between background and target noises for sleep disturbance, and (2) equivalent continuous A-weighted sound pressure levels during 24h for physiological effect. Environmental condition especially in nighttime and position where people are exposed to noise are also important parameters to be taken into consideration. In addition to the noise exposure meter, the measuring equipment developed includes thermohygrometer, illuminator and smartphone. We pursue portability and simplicity throughout the equipment. We suppose that subjects put on the noise exposure meter and the smartphone on their waist in daytime. Accuracy of the noise exposure levels at the waist is examined by simultaneous measurement near the ear at various scenes in our daily life. Long-term measurement of individual noise exposure that several subjects participate in is performed to verify the equipment. This report presents the results of preliminary measurements.

Evaluation of Sound Exposure and Risk of Hearing Impairment in Orchestral Musicians

This study aimed to assess exposure to sound and the risk of noise-induced hearing loss (NIHL) in orchestral musicians. Sound pressure level was measured in 1 opera and 3 symphony orchestras; questionnaires were filled in. On the basis of that data, the risk of NIHL was assessed according to Standard No. ISO 1999:1990. Classical orchestral musicians are usually exposed to sound at equivalent continuous A-weighted sound pressure levels of 81–90 dB (10th–90th percentiles), for 20–45 h (10th–90th percentiles) per week. Occupational exposure to such sound levels over 40 years of employment might cause hearing loss (expressed as a mean hearing threshold level at 2, 3, 4 kHz exceeding 35 dB) of up to 26%. Playing the horn, trumpet, tuba and percussion carries the highest risk (over 20%).