A-weighted Equivalent Sound Pressure Level Research Articles

Surface aging effects of long-term energized conductors on spectrum characteristics of audible noise

The impact of surface aging level of long-term energized conductors on spectrum characteristics of audible noise is studied in this paper. It is found that the average roughness and root-mean-square roughness of conductors increase with the operating time, namely the aging degree, through the quantitative measurement. A-weighted equivalent continuous sound pressure level (LAeq) is found to increase with the aging level. As the aging aggravation, the LAeq and its high-frequency components (>1 kHz) increase substantially and high-frequency components are mainly contributing to the increasing of LAeq. The high-frequency components (>1 kHz) of the new and aged stranded conductors have a marked increasing trend as the surface potential gradient increases, while the low-frequency components are mainly environment noise.

Short-term association between personal exposure to noise and heart rate variability: The RECORD MultiSensor Study

BackgroundStudies revealed long-term associations between noise exposure and cardiovascular health, but the underlying short-term mechanisms remain uncertain. ObjectivesTo explore the concomitant and lagged short-term associations between personal exposure to noise and heart rate variability (HRV) in a real life setting in the Île-de-France region. MethodsThe RECORD MultiSensor Study collected between July 2014 and June 2015 noise and heart rate data for 75 participants, aged 34–74 years, in their living environments for 7 days using a personal dosimeter and electrocardiography (ECG) sensor on the chest. HRV parameters and noise levels were calculated for 5-min windows. Short-term relationships between noise level and log-transformed HRV parameters were assessed using mixed effects models with a random intercept for participants and a temporal autocorrelation structure, adjusted for heart rate, physical activity (accelerometry), and short-term trends. ResultsAn increase by one dB(A) of A-weighted equivalent sound pressure level (Leq) was associated with a 0.97% concomitant increase of the Standard deviation of normal to normal intervals (SDNN) (95% CI: 0.92, 1.02), of 2.08% of the Low frequency band power (LF) (95% CI: 1.97, 2.18), of 1.30% of the High frequency band power (HF) (95% CI: 1.17, 1.43), and of 1.16% of the LF/HF ratio (95% CI: 1.10, 1.23). The analysis of lagged exposures to noise adjusted for the concomitant exposure illustrates the dynamic of recovery of the autonomic nervous system. Non-linear associations were documented with all HRV parameters with the exception of HF. Piecewise regression revealed that the association was almost 6 times stronger below than above 65 Leq dB(A) for the SDNN and LF/HF ratio. ConclusionPersonal noise exposure was found to be related to a concomitant increase of the overall HRV, with evidence of imbalance of the autonomic nervous system towards sympathetic activity, a pathway to increased cardiovascular morbidity and mortality.

Annoyance response and improvement of Zwicker's psychoacoustic annoyance model aiming at tonal noises

Zwicker’s psychoacoustic annoyance model can be used to estimate the relative degree of noise annoyance. However, this model cannot be well applied to compare the annoyance degrees of tonal noises and atonal noises. In order to improve its estimation effect on tonal noises, 3 groups of noise samples were selected randomly, i.e., 27 low-frequency tonal noise samples induced by a 1000 kV transformer with A-weighted equivalent sound pressure levels ranging from 41.2 dBA to 73.0 dBA; 30 low-, mid-, or high-frequency tonal/atonal noise samples with loudness levels ranging from 60 phon to 80 phon; and 60 other noise samples with A-weighted equivalent sound pressure levels ranging from 40.7 dBA to 75.0 dBA. Laboratory listening tests were conducted on the above 3 sample groups respectively via an 11-point numerical scale. The Zwicker’s psychoacoustic annoyance model was improved by taking tonality into account, and introducing the evaluation result of the first noise sample group (1000 kV transformer noise samples) to determine the coefficients in the model. The applicability of the improved model was examined by the evaluation results of the other two groups as well as the data in a previous research on annoyance of 220 kV/500 kV transformer noises. Results show that the improved model can estimate the relative annoyance degrees caused by various types of tonal / atonal noises much more accurately.

Sound quality evaluation of air-conditioner noise based on factors of the autocorrelation function

The aim of this paper is to clarify the characteristics of air-conditioner noise and determine the factor that is most influential on the subjective annoyance caused by this noise. The A-weighted equivalent continuous sound pressure level (LAeq) and factors extracted from the autocorrelation function (ACF) were analyzed. Subjective annoyance was evaluated using a paired comparison method. Multiple regression analyses were performed using a linear combination of LAeq, the ACF factors, and their standard deviations (SDs). The results indicated that the noise characteristics caused by each air conditioner and each operating level are determined by LAeq, and by the width of the first decay of the ACF, Wϕ(0), which corresponds to the spectral centroid. The multiple regression analyses indicated that the total subjective annoyance caused by air-conditioner noise can be predicted using the delay time and amplitude of the first maximum peak of the ACF (τ1 and ϕ1) and the SD of ϕ1. Annoyance was found to increase with decreasing τ1 and ϕ1, and with increasing ϕ1 SD, suggesting that noise components with higher pitches, weaker pitch strengths, and larger pitch strength variations cause greater levels of annoyance.

Levels and sources of neighbour noise in heavyweight residential buildings in Korea

Indoor noise level is a significant factor for occupants’ health, comfort, and psychological well-being in residential buildings; hence the World Health Organization (WHO) recommends guidelines for residential buildings based on the 24-h sound levels. However, only few studies have examined 24-h noise levels and sources from neighbours. Consequently, 24-h noise measurement is necessary for understanding noise level and acoustic comfort in homes. Field measurements were performed in 26 residential apartments in Korea to investigate levels and types of noise from neighbours. Noise recordings were carried out at each residence in unoccupied conditions. The recordings were analysed at 1min intervals in terms of the A-weighted equivalent (LAeq) and maximum sound pressure levels (LAFmax) for three different time periods during the day. It was found that 20 apartments met the recommended WHO guidelines during the daytime (07:00–23:00). However, at night (23:00–07:00), eight apartments were in excess of the WHO guideline value in terms of LAeq while LAFmax exceeded the WHO limit level in 22 apartments during the night. Human footsteps, movement of furniture, and dropping of small items were found to be major sources accounting for approximately 80% of all the noise events. LAFmax of children’s jumping and dropping small items were greater than others. Adults’ walking showed larger variation of noise levels than other sources. Moreover, it was found that indoor noise levels were not affected by slab thickness and major noise sources.

Feasibility of noise reduction by a modification in ICU environment

Noise is a proven cause of wakefulness and qualitative sleep disturbance in critically ill patients. A sound pressure level reduction can improve sleep quality, but there are no studies showing the feasibility of such a noise reduction in the intensive care unit (ICU) setting. Considering all available evidence, we redesigned two ICU rooms with the aim of investigating the physiological and clinical impact of a healing environment, including a noise reduction and day-night variations of sound level. Within an experimental design, we recorded 96 h of sound-pressure levels in standard ICU rooms and the modified ICU rooms. In addition, we performed a sound source observation by human observers. Our results show that we reduced A-weighted equivalent sound pressure levels and maximum sound pressure levels with our architectural interventions. During night-time, the modification led to a significant decrease in 50 dB threshold overruns from 65.5% to 39.9% (door side) and from 50% to 10.5% (window side). Sound peaks of more than 60 decibels were significantly reduced from 62.0% to 26.7% (door side) and 59.3% to 30.3% (window side). Time-series analysis of linear trends revealed a significantly more distinct day-night pattern in the modified rooms with lower sound levels during night-times. Observed sound sources during night revealed four times as many talking events in the standard room compared to the modified room. In summary, we show that it is feasible to reduce sound pressure levels using architectural modifications.

Audible Noise Measurement and Analysis of the Main Power Apparatus in UHV GIS Substations

Investigation of audible noise characteristics of the main power apparatus in UHV GIS substations provides essential statistics for the noise prediction and control. Noise pressure level, spectrum and attenuation characteristics of the main transformers and high voltage (HV) reactors are measured and analyzed in this paper. The result shows that the main transformer and HV reactor have identical A-weighted equivalent sound pressure level. The medium- and low-frequency noises are the primary components in the spectral. More attention should be paid to the low-frequency bands in the noise control process. The noise of cooling fan has a large influence on that of the main transformer. Without the consideration of corona noise, the average A-weighted sound pressure level shows an overall decreasing trend with the increase of the propagation distance. Obvious interference phenomenon of the noises at 100 and 200Hz exists in the noise propagation process.

Early indication of noise-induced hearing loss from PMP use in adolescents: A cross-sectional analysis.

Context:Distortion product otoacoustic emissions (DPOAEs) may indicate preclinical noise-induced hearing loss (NIHL) in adolescents from unsafe personal music player (PMP) use.Aims:The objective, therefore, was to observe preclinical signs of NIHL in 9th grade adolescents with clinically normal hearing by comparing DPOAE signals between different levels of A-weighted equivalent PMP exposure.Settings and Design:Subjects were recruited from all secondary-level schools located in the city of Regensburg, Germany during two academic years 2009/2010 and 2010/2011.Subjects and Methods:A-weighted equivalent sound pressure levels (SPLs) for a 40-hour work week (LAeq,40h) were estimated from questionnaire responses on output and duration of PMP use of the previous week. Subjects were then categorized into four levels of exposure: <80, 80–85, >85 to <90, and ≥90 A-weighted Decibel [dB(A)]. DPOAE signals were collected by trained audiological staff, applying a standard optimized protocol, at the Department of Otorhinolaryngology of the University Hospital Regensburg.Statistical Analysis Used:Mean DPOAE signals were compared between levels by unpaired t test. Novel linear regression models adjusting for other leisure noise exposures and with outcome variables DPoutcome and 4 kilo Hertz (kHz) DPOAEs estimated effects between levels.Results:A total of 1468 subjects (56% female, mostly aged 15 or 16 years) were available for analysis. Comparison of DPOAE means by PMP exposure typically showed no greater than 1 dB difference between groups. In fact, comparisons between ≥90 dB(A) and <80 dB(A) presented the least differences in magnitude. Both DPoutcome and 4 kHz linear regression models presented a weak association with the 4-level PMP exposure variable. An expected dose-response to PMP exposure was not observed in any analyses.Conclusions:DPOAE signal strength alone cannot indicate preclinical NIHL in adolescents.

Improvement of Zwicker’s psychoacoustic annoyance model aiming at tonal noises

According to 4 acoustical parameters of noise samples (i.e., loudness, sharpness, fluctuation strength and roughness), Zwicker’s psychoacoustic annoyance model can be used to estimate the relative degree of noise annoyance. However, this model cannot be well applied to compare the annoyance degrees of tonal noises and atonal noises. In order to improve its estimation effect on tonal noises, 3 groups of noise samples were selected randomly, i.e., 27 low-frequency tonal noise samples induced by a 1000kV transformer with A-weighted equivalent sound pressure levels ranging from 41.2dBA to 73.0dBA; 30 low-, mid- or high-frequency tonal/atonal noise samples with loudness levels ranging from 60 phon to 80 phon; and 60 other noise samples with A-weighted equivalent sound pressure levels ranging from 40.7dBA to 75.0dBA. Laboratory listening tests were conducted on the above 3 sample groups respectively via an 11-point numerical scale. The Zwicker’s psychoacoustic annoyance model was improved by taking tonality into account, and introducing the evaluation result of the first noise sample group (1000kV transformer noise samples) to determine the coefficients in the model. The applicability of the improved model was examined by the evaluation results of the other two groups as well as the data in a previous research on annoyance of 220kV/500kV transformer noises. Results show that the improved model can estimate the relative annoyance degrees caused by various types of tonal/atonal noises much more accurately.

Development and validation of a new adaptive weighting for auditory risk assessment of complex noise

Noise-induced hearing loss (NIHL) still remains as a serious occupational related health problem worldwide. A-weighted equivalent sound pressure level (SPL) LAeq has been widely used to assess the auditory risk of occupational noises in noise measurements standards. In addition, C-weighting is also used in the standards for detection of peak SPL of noise. However, both A-weighting and C-weighting have limitations on evaluation of high-level complex noise, which is often experienced in many military and industrial fields. In this study, we proposed a new adaptive weighting (F-weighting) for more accurate evaluation of complex noises. F-weighting is based on the blending of A-weighting and C-weighting through the weighting coefficients αA,T and αC,T. To determine αA,T and αC,T, two parameters, kurtosis (KT) and oscillation coefficient (OT) were introduced. Complex noise exposures in animal studies and noise signals measured in a mining facility were applied to validate the performance of F-weighting. The results show that F-weighting performs better than both A-weighting and C-weighting on the assessment of high-level complex noise. In addition, F-weighting based LFeq shows higher correlation with the hearing loss of the animal experimental data compared with A-weighted LAeq, C-weighted LCeq, and Non-weighted Leq. The proposed F-weighting could be a potential alternative weighting for the assessment of high-level complex noise in military and industrial applications.

Experimental verification of differences in subjective annoyance responses using a jury test to compare the noise emissions of straight and curved sections of an urban railway

The urban railway, which has both ground-level and underground sections, is a major means of transportation in the city of Seoul. Environmental noise problems have been encountered in residential areas near the railway on ground-level sections. To assess the extent of this problem, many countries have adopted the method of A-weighted equivalent sound pressure level ( LpAeq). However, it may be not reasonable to apply the same evaluation method on all sections of a railway, since the acoustic characteristics of railway noise are highly variable, and its effect on human psychology is complex. Thus, since each person reacts differently to noise, psychological approaches have been utilized to analyze the effects of noise. The aim of this study is to determine an appropriate method for the assessment of railway-generated noise. First, the characteristics of railway-generated noise on straight and curved sections of track were compared by looking at aspects such as the waveforms of the sound pressure and the characteristics of frequency patterns. After that, the subjective annoyance response was analyzed by performing a jury test and a survey in order to understand how people react differently to similar sounds on the two test sections of track.

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.

Effects of Acoustic Treatment on Music Teachers' Exposure to Sound

Abstract In this study, music teachers' exposure to sound was tested by measuring the A-weighted equivalent sound pressure level (SPL), the A-weighted maximum SPL and the C-weighted peak SPL. Measurements were taken prior to and after acoustic treatment in four rooms during classes of trumpet, saxophone, French horn, trombone and percussion instruments. Results showed that acoustic treatment affects the exposure of music teachers to sound. Daily noise exposure levels (LEX, 8 h) for all teachers exceeded a limit of 85 dB while teaching music lessons prior to room treatment. It was found that the LEX, 8 h values ranged from 85.8 to 91.6 dB. The highest A-weighted maximum SPL and C-weighted peak SPL that music teachers were exposed to were observed with percussion instruments (LAmax = 110.4 dB and LCpeak = 138.0 dB). After the treatments, daily noise exposure level decreased by an average of 5.8, 3.2, 3.0, 4.2 and 4.5 dB, respectively, for the classes of trumpet, saxophone, French horn, trombone and drums, and did not exceed 85 dB in any case.

Annoyance response to low frequency noise with tonal components: A case study on transformer noise

In order to study how acoustical factors influence annoyance responses to low frequency noise with tonal components, this research has selected 220kV and 500kV transformer noises as examples and an 11-point numerical scale as an evaluation tool, in which the percentage of highly annoyed (%HA) and mean annoyance (MA) are chosen to represent annoyance caused by noises. Results show that a logistic curve is well suited for describing the exposure–response relationship between the A-weighted equivalent sound pressure level (LAeq) and %HA (or MA) of the transformer noise. With the same LAeq, 220kV transformer noise is more annoying than 500kV transformer noise in terms of %HA and MA, which is related to different sharpness, roughness and tonality of the noises caused by transformers of the two voltage levels. Based on stepwise regression analysis, multiple linear regression models are further developed by using LAeq and roughness as acoustical parameters to predict the %HA and MA of transformer noise. Compared with the linear regression model that considered only LAeq values, multiple linear regressions can efficiently account for the different annoyance ratings of the two transformer noises at the same LAeq values.

Annoyance and activity disturbance induced by high-speed railway and conventional railway noise: a contrastive case study

BackgroundHigh-speed railway (HR, Electrified railway with service speed above 200 km/h.) noise and conventional railway (CR, Electrified railway with service speed under 200 km/h.) noise are different in both time and frequency domain. There is an urgent need to study the influence of HR noise and consequently, develop appropriate noise evaluation index and limits for the total railway noise including HR and CR noise.MethodsBased on binaural recording of HR and CR noises in a approximate semi-free field, noise annoyance and activity disturbance induced by maximal train pass-by events in China were investigated through laboratory subjective evaluation. 80 students within recruited 102 students, 40 males and 40 females, 23.9 ± 2.1 years old, were finally selected as the subjects. After receiving noise stimulus via headphone of a binaural audio playback system, subjects were asked to express the annoyance or activity disturbance due to railway noise at a 0-100 numerical scale.ResultsThe results show that with the same annoyance rating (A) or activity disturbance rating (D), the A-weighted equivalent sound pressure level (LAeq) of CR noise is approximately 7 dB higher than that of HR noise. Linear regression analysis between some acoustical parameters and A (or D) suggests that the coefficient of determination (R2) is higher with the instantaneous fast A-weighted sound pressure level (LAFmax) than that with LAeq. A combined acoustical parameter, LHC = 1.74LAFmax + 0.008LAFmax(Lp-LAeq), where Lp is the sound pressure level, was derived consequently, which could better evaluate the total railway noise, including HR and CR noise. More importantly, with a given LHC, the noise annoyance of HR and CR noise is the same.ConclusionsAmong various acoustical parameters including LHC and LAeq, A and D have the highest correlation with LHC. LHC has been proved to be an appropriate index to evaluate the total railway noise, including both HR and CR. However, it should be pointed out that this study provides suggestive evidence, rather than a final proof. Further study is expected to elucidate conclusions above by additional measurements.

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.

Assessment of rural soundscapes with high-speed train noise

In the present study, rural soundscapes with high-speed train noise were assessed through laboratory experiments. A total of ten sites with varying landscape metrics were chosen for audio-visual recording. The acoustical characteristics of the high-speed train noise were analyzed using various noise level indices. Landscape metrics such as the percentage of natural features (NF) and Shannon's diversity index (SHDI) were adopted to evaluate the landscape features of the ten sites. Laboratory experiments were then performed with 20 well-trained listeners to investigate the perception of high-speed train noise in rural areas. The experiments consisted of three parts: 1) visual-only condition, 2) audio-only condition, and 3) combined audio-visual condition. The results showed that subjects' preference for visual images was significantly related to NF, the number of land types, and the A-weighted equivalent sound pressure level (LAeq). In addition, the visual images significantly influenced the noise annoyance, and LAeq and NF were the dominant factors affecting the annoyance from high-speed train noise in the combined audio-visual condition. In addition, Zwicker's loudness (N) was highly correlated with the annoyance from high-speed train noise in both the audio-only and audio-visual conditions.

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.

Noise pollution in urban settings of the Western Amazonia and an approach to cope with

The Amazon Region is usually well known for its nature and not for the noise pollution that recently took over in many cities, both major ones such as Porto Velho, Manaus, or Belém, as well as minor cities. Transparent facades with large openings of places like restaurants and bars, heavy traffic, and young adults competing with high power car sound systems are the most common sources of noise pollution and annoyance. Results from noise measurements done at different moments at several “hot spots” in Porto Velho, capital of the state of Rondônia, will be presented. A-weighted equivalent sound pressure levels at all measurement points were found to be in exceedance of 70 dBA during several hours at night, causing a lot of annoyance to the population. Besides the results of measurements some results of the state authorities approach to combine a campaign to raise noise awareness and noise policy enforcement will be presented.

Analyses of adjustment of the impulse noise

Impulse noise is one of the most hazardous and annoying types of noise, which is present in the working and community environment. A-weighted equivalent sound pressure level, describing most types of noise, appears not to be the appropriate descriptor, especially not for high-impulsive and high-energy impulsive noise. However, this descriptor is often used as a basis for impulse noise evaluation, when combined with appropriate adjustment terms. But despite of objective character of such evaluation, care should be taken regarding certain facts, especially the source of impulse noise, its environment and time of measurement. In this article, the relationships between all these influential parameters have been investigated in detail. Today, on the other hand, a sophisticated sound level meter offers the possibility of simultaneous measurement of many acoustical descriptors. By combining some of these descriptors with some analytical investigations, as shown in this article, more useful information concerning impulse noise can be obtained. In this article some of them are used for more detailed analysis of impulse correction, according to some international standards.