Equivalent Continuous Sound Pressure Level Research Articles

Experimental study to measure the sound transmission loss and equivalent continuous sound pressure level of composite material for various disturbances

In this paper, the sound transmission loss (STL) and equivalent continuous sound pressure level (Leq) of the polypropylene/glass fiber reinforced material has been measured experimentally. The objective of the present work is to measure the sound absorption properties of the polypropylene/glass fiber reinforced composite material for various real case disturbances. The real case disturbances are harmonic sound (one-third octave band frequencies), road traffic noise, ambulance siren noise, train noise, aircraft noise, construction and machinery noise. The acoustical behavior of the composite material is then compared with the neat polypropylene and with window glass, termed as a single glass. The diameter and the thickness of the composite specimens are 152 mm and 4 mm respectively. The acoustical behavior of the composite material is experimentally measured at different fiber volume fractions. The fiber volume fraction (Vf) used in the present work is 10%, 20%, and 30%. Also, the fiber orientation, ranges from 0° to 90°, considers an important factor on the acoustical behavior of the composite material. The results are also compared with the two glasses separated with an air, termed as a double glass.

Experimental study to measure the transmission loss of double panel natural fibers

In this paper, the transmission loss (TL) of the natural fiber materials will be measured experimentally at one third octave band harmonic and broadband frequencies. The different natural fibers used in this study are jute fibers, kenaf fibers, banana fibers, coconut coir fibers, and hemp fibers. An acoustic soundproof cabin has been fabricated to measure the transmission loss of natural fiber material. A one-dimensional duct is placed inside the soundproof cabin. Inside the duct there is a specimen of natural fiber materials. A loudspeaker is used to generate acoustic harmonic and white noise disturbances at various frequencies. The generated acoustic sounds then passed through the double panel natural fiber specimens. A sound pressure level (SPL) meter is used to measure the noise levels inside the duct. In this paper, a double panel natural fiber material specimen is proposed for testing. The double panel specimens are a combination of two natural fiber materials. In the double panel, the two panels are made from same or different natural fibers and also air is enclosed between them. The main objective of this paper is to measure the transmission loss and equivalent continuous A-weighted sound pressure level of fiber-air-fiber type specimens so that in future these types of combinations can be used for various engineering and other applications. It is observed that the combination of jute-air-kenaf is absorbing more sound as compared to jute-air-banana fibers and hemp-air-coconut coir fibers.

Dynamic properties of peak levels of road traffic noise along a freeway

The hourly traffic volume at night is typically lighter than that during the day. However, the average speed and the rate of heavy vehicle tend to be higher at night. It is shown that the influence of the maximum A-weighted sound pressure level (LA,Fmax) is much more dominant in the night than during the day in the roadside areas of a highway. In order to predict and evaluate the traffic noise in the areas facing the road and to investigate the influence on the health effects of the residents living in such areas, it is indispensable accurately to grasp not only the equivalent continuous A-weighted sound pressure level but also the LA,Fmax and the dynamic properties of level fluctuation of noise.

Aircraft noise exposure assessment for a case-crossover study in Switzerland

TPS 781: Health effects of noise, Exhibition Hall, Ground floor, August 27, 2019, 3:00 PM - 4:30 PM Background: The long-term effects of transportation noise on sleep quality, annoyance and cardiovascular diseases (CVDs) are being increasingly recognized. However, little is known about the triggering effects of noise on CVDs. To investigate the acute effects of aircraft noise on CVD mortality by means of a case-crossover study, a reliable and detailed noise exposure assessment is required. Methods: Individual aircraft noise exposures were assessed for a selected population from the Swiss National Cohort (SNC) residing around Zürich Airport in Switzerland. Outdoor noise was estimated at participants’ home addresses for case and control events, combining modeled aircraft noise with all registered flight movements between 2000 and 2016. Different noise metrics including equivalent continuous sound pressure level (LAeq), maximum sound pressure level (LAmax) or number above threshold 55 dB (NAT55) were used to quantify and characterize the noise impact during different night-time exposure windows. Results: Aircraft noise levels were generally highest during the evening time window (19 to 23) and lowest during the core night (23:30 to 06). Average LAeq were 46, 38, 21, 38 and 33 dB for the different time windows (19-23, 23-23:30, 23:30-06, 06-07 and 23-07 respectively). Average LAmax were 65, 53, 46, 53 and 58 dB and average NAT55 19, 1, 0, 2 and 4 for the same intervals. Average LAeq, LAmax and NAT55 during the two hours preceding night-time deaths for all case and control events were 34 dB, 52 dB and 3, respectively. Conclusion: This study is the first to provide individual aircraft noise exposures with high temporal resolution, using a list of movements and previously calculated aircraft noise footprints for different aircraft types and air routes at various times. The choice of the exposure events is flexible and precise, making this approach attractive for conducting a case-crossover study investigating short-term effects of noise on health.

The temporary hearing thresholds shifts in fitness instructors

Noise in the entertainment industry often reaches high sound pressure levels. The aim of this study was to analyze the temporary threshold shifts (TTSs) of hearing among fitness instructors. The study comprised a total of 30 fitness instructors working in fitness clubs. The noise dosimeters were used to determine individual noise exposure during exercises conducted by the instructors. To assess the TTS values, the pure tone audiometry tests were performed before and just after the exercises. The observed TTSs were compared with the predicted TTSs according to the computational model developed by Melnick (1991). Typical fitness exercises lasted from 1 to 2 h and A-weighted equivalent-continuous sound pressure level ranged from 75 to 96 dB. Temporary threshold shifts after the sound exposure were statistically significant. The actual values of TTS fitted well with the values predicted with the TTS computational model. The results show that the computational TTS model gives results consistent with the TTS observed in the study group. Fitness instructors constitute a population at an increased risk of the hearing loss. Raising awareness of this fact and implementing hearing protection programs in this group of workers are urgently needed.

Evaluation of noise exposure and risk of hearing impairment in judicial transcribers

The aim of this study was to evaluate noise exposure and risk of hearing impairment in judicial transcribers. Noise measurements and questionnaire inquiry were carried out in a group of 15 employees, aged 38.0 ± 0.8 years. Sound pressure levels emitted by headphones were measured using the MIRE technique according to ISO 11904-1:2008. The risk of noise-induced hearing loss was estimated according to the guidelines of ISO 1999:2013.The diffuse-field-related A-weighted equivalent-continuous sound pressure levels measured under headphones reached values from 62 to 80.7 dB. The study subjects worked as transcribers on average for 4–7 h a day. Consequently, the individual daily noise exposure levels in the examined group ranged from 61.2 to 79.9 dB. Such exposures for 10 years of occupational work pose a risk of hearing impairment (the mean hearing threshold at frequencies of 2, 3, and 4 kHz > 20 dB) reaching 3.5%. Almost three fourth of the employees reported their hearing deterioration (73.3%), whereas nearly a half of them experienced temporary hearing symptoms due to usage of headphones (43.3%).It is recommended that the transcribers should be covered by the hearing protection programme.

Perceived Occurrences of Soundscape Influencing Pleasantness in Urban Forests: A Comparison of Broad-Leaved and Coniferous Forests

Perceived occurrences of soundscape reflect cognitive responses to perceived soundscapes. This research focuses on the relationship between perceived occurrences and pleasantness of soundscape in urban forests, and models these parameters. Soundscape information was gathered at 60 observation sites in urban forests, including perceived occurrences of soundscape (POS), pleasantness of perceived soundscape in urban forests (PSUF), and equivalent continuous A-weighted sound pressure level (LAeq). Twelve trained participants were exposed to the soundscape at each site for five minutes and filled out a questionnaire about POS and PSUF. The weight-ratio of perceived occurrences of soundscape (WPOS) was obtained from the POS. Pearson’s correlation coefficients and Stevens’ power law were conducted to test the applicability of the perceived occurrences of soundscape in psychophysical models. Results show that there is an interaction between the WPOS and PSUF in urban forests, and that psychophysical models are able to assess pleasantness of perceived soundscapes in urban forests. Findings show that pleasantness trends of geophony and biophony in broad-leaved forests and those in coniferous forests are opposite when the LAeq is increasing. Furthermore, by combining the WPOS, PSUF, and LAeq, the models were able to link the PSUF of geophony, biophony, anthrophony, and total soundscape in urban forests. Overall, results revealed that perceived occurrences of soundscape play a key role in linking the pleasantness of geophony, biophony, and anthrophony in urban forests.

The Effects of Noise and Heat Strain on the Work Ability Index (WAI) among Rubber Factory Workers.

Introduction:Assessing the work ability and factors affecting it is essential in developing strategies for preventing damages and managing risks. This study aimed to investigate the simultaneous effect of noise level and physiological strain as well as individual characteristics on the work ability.Method:The population in this cross-sectional study included workers of a rubber factory. The TES noise dosimeter was used to examine individual exposure and the electro polar RS100 was used to measure physiological strain index (PSI). Individual characteristics and the work ability index were evaluated using the WAI questionnaire and analyzed using SPSS version 19. chi-square test, pearson correlation coefficient, and one-way and multiple ANOVA were used for data analysis.Results:The final modeling showed that age, exercising period, Equivalent Continuous Sound Pressure Level (Leq), PSI and employment status had significant correlations with the work ability index (p < 0.05). The modified r2 for the obtained model was also calculated to be 0.483.Discussion and conclusion:Based on the findings, number of exercising hours, employment status, age, Leq, and psi are among the factors affecting the work ability index. Use of management and engineering controls are recommended to balance work environments exposed to noise and heat and improve the work ability index. Further, improving employment status due to creating a sense of stability and reducing stress as well as enhancing lifestyle quality can be effective in increasing the work ability index.

Effects of combined traffic noise on the synaptic ultrastructure and expressions of p-CaMKII and NMDAR1 in the hippocampus of young SD rats.

In order to explore the effects of combined traffic noise (CTN) on learning and memory function, young Sprague-Dawley (SD) rats were exposed to CTN from highway and high-speed railway for 52days, whose day-night equivalent continuous A-weighted sound pressure level (Ldn) was 70dB(A) (corresponding sound pressure level was 80dB). The synaptic ultrastructure and the expressions of phosphorylated calcium/calmodulin-dependent protein kinase II (p-CaMKII) and N-methyl-D-aspartate receptor 1 (NMDAR1 or NR1) in the hippocampus were tested by transmission electron microscopy (TEM) and Western blot, respectively. Results showed that there was no significant difference in the synaptic ultrastructure and the expressions of p-CaMKII and NR1 in the hippocampus of young rats between the experimental group and control group. Compared with single high-speed railway noise (HSRN) with Ldn of 70dB(A), CTN had less influences on learning and memory function, which was closely related to smaller intermittency of CTN and less anxiety caused by CTN. In comparison with white noise with a sound pressure level of 80dB, CTN had less impacts on learning and memory function, which was mainly associated with CTN's smaller R-weighted sound pressure level based on rats' auditory sensitivity.

Factors influencing the harmonious degree of soundscapes in urban forests: A comparison of broad-leaved and coniferous forests

This study analyzed the relationship between the physical quantity of soundscape and the psychological quantity for humans in different urban forest spaces based on the soundscape harmonious degree and the physical index found in broad-leaved and coniferous forest spaces. Three soundscape parameters were conceived: the soundscape harmonious degree (SHD), total harmonious degree of soundscape (THDS), and equivalent continuous A-weighted sound pressure level (LAeq). These were used to analyze the relationship between objective and subjective soundscapes in urban forests and structured according to the subjective and objective transformation model of soundscape harmonious degree in urban forests. Results suggest that the distributions of biophony and anthrophony evaluation scores in a coniferous forest are more concentrated than in a broad-leaved forest, while the distribution trend of geophony is the opposite. This study found three stages of coordinated soundscape perception, both in broad-leaved and coniferous forests, including: a reduction in difference, a stationary difference, and an increase in difference. The law of psychophysics can be applied to soundscape harmonious degree and LAeq in broad-leaved and coniferous forests. Overall, the results revealed that although there are differences in soundscape harmonious degree between the geophony, biophony and anthrophony in forests, these soundscapes exhibit a pattern when their soundscape harmonious degree is simultaneously analyzed in an ordered sequence of LAeq.

A study evaluating noise levels at selected schools in the Czech Republic.

Worldwide, primary schools are the most important segment of childhood education. The main disturbing source of noise in schools is human speech, the primary component of the learning process. School noise has a negative impact on information processing, teachers and pupils, and communication in the classroom. The study aimed at assessing A-weighted sound pressure levels in primary school classrooms. It was concerned with A-weighted sound pressure levels and their fluctuation during various classes. The noise was measured with the static calibrated Brüel and Kjær 2260 Investigator sound level meter. The sound pressure levels were measured twice in 12 classes as 11 different subjects were taught to reduce the uncertainty of results due to their potential variability in time. From the instantaneous values, LA (t), equivalent continuous A-weighted sound pressure levels (LAeq,T) and LAmax were calculated. The mean equivalent A-weighted sound pressure level during lessons irrespective of age and subjects taught was 68.0 ± 3.4 dB (uncertainty of measurement). The highest levels of noise were in physical education and arts; the lowest levels were found for English taught as a foreign language. There were no statistically significant differences in LAeq,T depending on the numbers of children in the classes. The main source of noise is pupils. Attention should be paid to negative feelings of noise to reduce LAeq,T in schools. Continuous noise pollution, in combination with stress and the mentally demanding nature of the teaching profession, may lead to numerous negative effects on human personality.

Prediction of noise from wind turbines: theoretical and experimental study

Several noise propagation models used to calculate the noise produced by wind turbines have been reported. However, these models do not accurately predict sound pressure levels. Most of them have been developed to estimate the noise produced by industries, in which wind speeds are less than 5 m/s, and conditions favor its spread. To date, very few models can be applied to evaluate the propagation of sound from wind turbines and most of these yield inaccurate results. This study presents a comparison between noise levels that were estimated using the prediction method established in ISO 9613 Part 2 and measured levels of noise from wind turbines that are part of a wind farm currently in operation. Differences of up to 56.5 dBZ, with a median of 29.6 dBZ, were found between the estimated sound pressure levels and measured levels. The residual sound pressure levels given by standard ISO 9613 Part 2 for the wind turbines is larger for high frequencies than those for low frequencies. When the wide band equivalent continuous sound pressure level is expressed in dBA, the residual varies between −4.4 dBA and 37.7 dBA, with a median of 20.5 dBA.

Identification of urban park activity intensity at different thermal environments and visible sky by using sound levels.

An efficient urban environmental design considers appropriate thermal comfort condition, shaded space, and activity intensity. Physiologically equivalent temperature (PET) and visible sky, i.e., the sky view factor (SVF), are usually used as indicators to determine the outdoor thermal comfort and amount of shaded space, respectively. The activity intensity in urban parks, which is dependent on culture and micrometeorological conditions, was represented inappropriately by attendance density in Taiwan. To optimize the park design and improve the park utilization rate in Taiwan, several environmental factors such as sound pressure levels and numbers of park visitors were measured, and PET values and SVF values were calculated from primary micrometeorological data such as wind speed and globe temperature. This study proposed equivalent continuous sound pressure level (Leq) as a novel indicator to represent park activity intensity and investigated the correlation between Leq and SVF at different PET values. Leq was more appropriate than was attendance density in representing the park activity intensity in Taiwan. In addition, Leq was highly negatively correlated with SVF when visitors felt that the outdoor thermal comfort condition was hot or very hot. In other words, a lower degree of shading in the park resulted in lower activity intensity. Park visitors tended to engage in activities in the shaded regions because of more favorable thermal comfort conditions (i.e., neutral PET). The established quantitative relationships among Leq, PET, and SVF can serve as a reference for park planning.

A case study of smartphone based platform for mapping and analyzing environmental noise in Singapore

In this paper, we present a smartphone based platform for mapping and analyzing environmental noise. Smartphones are used to record environmental noise (both audio and sound pressure level) as well as locations (latitude, longitude, and accuracy). The recorded data is uploaded to a server and noise map of a region is generated using the location information along with the sound pressure levels (SPL) at those locations. Noise maps can used to discover sources of noise in a region and also to compare SPL between different places. Thus, they can be an important tool to help implement mitigating steps for reducing noise or planning future developments. To illustrate the capabilities of the platform, we present a case study of noise mapping with five educational institutes and five residential neighborhoods in Singapore. We present noise maps for these places and discuss possible sources of noise. We also discuss potential reasons for observed differences in equivalent continuous sound pressure level between different educational institutes, and residential neighborhoods.

A laboratory investigation into the effect of quiet-time interval between aircraft noise events on overall noisiness.

In order to investigate the effect of the quiet-time interval between aircraft noise events on the overall negative impression of aircraft noise, psychological experiments were conducted in which the quiet-time interval was varied and the number of events and duration of each stimulus were taken into account. For equal A-weighted equivalent continuous sound pressure level (LAeq) among the stimuli, it was found that overall noisiness decreased as the quiet-time interval ratio of the stimulus was increased. It was also found that the correlation between overall noisiness and LAeq was improved by adjusting for the quiet-time interval ratio or the number of events included in the stimuli, especially when participants paid attention to changes in the instantaneous noise level. This study reveals that LAeq is a good basis for evaluating the negative impressions of aircraft noise, but that correcting for the quiet-time interval and/or number of flights improves the correlation between LAeq and the negative impression in such aircraft noise situations.

Traffic Noise Assessment at Residential Areas in Skudai, Johor

Vehicles passing by on roadways in residential areas may produce unpleasant traffic noise that affects the residents. This paper presents the traffic noise assessment of three selected residential areas located in Skudai, Johor. The objectives of this study are to evaluate traffic characteristics at selected residential areas, determine related noise indices, and assess impact of traffic noise. Traffic characteristics such as daily traffic volume and vehicle speed were evaluated using automatic traffic counter (ATC). Meanwhile, noise indices like equivalent continuous sound pressure level (LAeq), noise level exceeded 10% (L10) and 90% (L90) of measurement time were determined using sound level meter (SLM). Besides that, traffic noise index (TNI) and noise pollution level (LNP) were calculated based on the measured noise indices. The results showed an increase in noise level of 60 to 70 dBA maximum due to increase in traffic volume. There was also a significant change in noise level of more than 70 dBA even though average vehicle speed did not vary significantly. Nevertheless, LAeq, TNI, and LNPvalues for all sites during daytime were lower than the maximum recommended levels. Thus, residents in the three studied areas were not affected in terms of quality of life and health.

NOISE MAPPING OF CELAL BAYAR BOULEVARD AND THE NOISE EXPOSURE ANALYSIS OF HIGHWAY NOISE SPECIFICALLY FOR EDUCATIONAL AND HEALTH BUILDINGS

This study was carried out to determine and evaluate the noise control analyses and noise mapping studies performed by the measurement and simulation program for the road traffic noise on Celal Bayar Boulevard in Ankara. Method: In this context, in the selected sample study area, a noise map was created using the CadnaA simulation program in the light of the data obtained through environmental noise measurements (Ldaytime, Levening, Lnight) and vehicle counts, and the measurement and simulation program results obtained were compared. Then, the facade measurements were performed in Gazi University Faculty of Engineering and Architecture Building, Ankara University Faculty of Medicine Deanship and Morphology Building and Hacettepe University Hospital Building specifically for educational and health buildings located on Celal Bayar Boulevard, and the facade analysis was performed using the CadnaA simulation program. Findings: In the study, according to the noise map data generated by the CadnaA simulation program, it was determined that there was an equivalent continuous sound pressure level (Leq) between 70.5 – 81.8 dBA during the daytime, between 64.6 – 76.9 dBA during the evening hours, between 58.6 – 71.7 dBA during the night hours, and between Lgag 69.8 – 81.7 dBA along Celal Bayar Boulevard. Conclusion: As a result of this study, it was observed that the noise maps and action plans planned to be revised with simulation programs every 5 years should be measured and supported.

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 (&amp;gt;1 kHz) increase substantially and high-frequency components are mainly contributing to the increasing of LAeq. The high-frequency components (&amp;gt;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.

Tractor Noise Levels Impact on Operator Safety

Acoustic noise is one of the most persistent pitfalls of the operators of construction, mining and agricultural machineries, predominantly hearing loss or weak hearing. Also noise include decreased productivity, increased heart rate, and increased blood pressure, startle reaction, and other cardiovascular and psychophysiological system changes (Mansoor, et al. 2011, 2012). The aim of this reaserch was to investigate the impact of noise levels emitted from the agricultural tractors under field operations on the operator safety. Three types of tractors used in this study were Nasr, Belarus and Universal/UTB (Romani). They are without cabin and represent about 76% of the total number of tractors used in Egypt (Economic affair sector, 2012). The noise emitted from them was monitored and evaluated under plowing and land leveling operations as a heavy duty operation field. The data was collected at different engine speed and gears as recommended by the operator for each operation. Measurements of noise levels were taken with the use of Cirrus CR 110A doseBadge and RC 110A reader unit. The noise level measurements were performed in accordance with the Egyptian environmental law (EEL) number 4/1994 modified issue in 2012. Results show that the sound pressure level (SPL) in operator ear and the noise dose % from all tractors under all cases were more than EEL allowable 90 dBA criterion level for 8 hour of operation. The obtained results indicated that the noise levels with “A” frequency weighting (LAeqdB) for all tractors loaded with chisel plow were the highest measured values. The noise levels emitted from the Nasr tractor were the highest and ranged from 102 to 107 dBA, for Belarus tractor were ranged from 99 to 105 dBA and for UTB tractor were ranged from 96 to 104 dBA. The daily noise exposure levels (Lex(8)dB) from Nasr, Belarus and UTB tractors were 105, 102 and 100 dBA and the corresponding noise dose % as function of equivalent-continuous sound pressure level were 800%, 560% and 400% respectively. The results showed that there was highly significant difference in the systolic blood pressure (SBP) before and after work shift. Similar results were found for the diastolic blood pressure (DBP). For the classification of blood pressure among the operators before and after work shift, majority of the operators was under stage one hypertension (64.5 %), followed by pre-hypertension (28.4 %) and stage two hypertension (7.1%). This study showed that there was association between noise exposure and blood pressure among the operators. It is recommended that; the tractors operators must use one of hear protecting tool to increase working hours, arrange work schedules to let operators exchange work activities so that no one person is exposed to the noise for more than permissible hours in one day and proved tractors with a cabin for the tractors types under this study.

The Hearing Threshold of Employees Exposed to Noise Generated by the Low-Frequency Ultrasonic Welding Devices

Abstract The aim of the study was to assess the hearing threshold levels (HTLs) in employees exposed to noise generated by low-frequency ultrasonic technological equipment in comparison with the HTLs of workers exposed to audible noise at the similar A-weighted equivalent-continuous sound pressure level. The study includes measurements of ultrasonic and audible noise at workplaces and hearing tests, i.e. conventional pure-tone audiometry and extended high-frequency audiometry. The study group comprised 90 workers, aged 41.4±10.0 years (mean±SD), exposed for 17.3±9.8 years to noise generated by ultrasonic devices at mean daily noise exposure level (‹LEX,8h›) of 80.6±2.9 dB. The reference group consists of 156 subjects, exposed to industrial noise (without ultrasonic components) at similar A-weighted equivalent-continuous sound pressure level (‹LEX,8h› = 81.8±2.7 dB), adjusted according to age (39.8±7.7 years), gender and job seniority (14.0±7.0 years). This group was selected from database collected in the Nofer Institute of Occupational Medicine. Audiometric hearing threshold levels in the frequency range of 0.5-6 kHz were similar in both groups, but in the frequency range of 8-12.5 kHz they were higher in the group of employees exposed to ultrasonic noise. The findings suggest that differences in the hearing threshold (at high frequencies) in analyzed groups may be due to differences in spectral composition of noise and show the need to continue the undertaken studies.