Equivalent Sound Pressure Level Research Articles

A Sound Level Meter featured with automatic estimation of the measurement uncertainty

In the area of measuring the environmental noise the equivalent sound pressure level LA,eq is adopted and compared with legal thresholds in order to characterize the site of interest. The paper describes an innovative Sound Level Meter (SLM) able to provide information about the measurand contribution to the measurement uncertainty estimation. This measurement technology is made possible thanks to an approach based on bootstrap method for selecting the suitable measurement episode for an estimation of LAeq. The firmware implementation of the developed SLM is disclosed with reference to a low-cost platform for real-time execution of the proposed methodology. Finally, a metrological characterization of the prototype performed in laboratory is reported as well as the performance comparison with a class 1 SLM in a real scenario. As a result, the smart features of the new SLM may be easily implemented by including commercial devices into the instrument schematics.

A Computer simulation of noise of construction machinery operating in parallel

Prolonged, repeated or very intense noise exposure can damage human health. To reduce any dangerous effects of noise on human health, policies and restrictions are enshrined in national law and legislative regulations. In the Czech Republic, this issue is subject to the Ministry of Health. In other states it can be the Ministry of Health or more often the Ministry of the Environment. The protection of human health against noise and vibration is enshrined in Act No. 258/2000 Coll., on Protection of Public Health, specifically in şş 30-34 of this Act. Other restrictions are described in Act No. 309/2006 Coll., which regulates other requirements for safety and health protection at work in labour relations and on ensuring safety and health protection in activities or the provision of services outside of labour relations. Furthermore, hygienic limits for workplaces, protected indoor areas of buildings and protected outdoor areas are set in the new Regulation of the Government of the Czech Republic, No. 272/2011 Coll. as amended. This Regulation also sets limits for construction noise. They set limitations in so-called outdoor protected areas and the so-called outdoor protected areas of buildings. The hygienic limit of the equivalent sound pressure level A for noise from construction activities is set here by adding a correction of 5dB or 15dB according to the type of protected space to the basic value of the equivalent sound pressure level A 50dB. This limit must be adhered to. For buildings nearby, the term „protected facades“ is used, i.e. „protected façades“ include the nearest buildings that are inhabited and their occupants could be exposed to noise for a long period of time. We can measure the intensity of noise in these places if we have a "sound level meter". Predicting the intensity of noise and its longevity for future construction is more challenging. The computational evaluation of the noise load of the outdoor area of the monitored territory is based on the recommended theoretical acoustic relations for the transmission of sound from stationary noise sources according to ČSN ISO 9613/1-2. One of the possibilities of calculating the intensity of noise is the application of software programmes used for determining traffic noise, which, in contrast to construction noise, is handled very carefully and predicted in detail during the construction of transport infrastructure. Because here are the values and methodologies for the calculation of noise indicators set correctly and in detail, it is possible to use them also, provided that we work well with the background and input data. The calculation indicators are the values of the equivalent sound pressure level falling in front of the façade, on which we determine various measuring points. If the noise sources and acoustically significant elements are entered correctly, we obtain both correct values and also the possibility of displaying a map of the area with colour isophone bands, which expresses the level of noise in the construction site and its surroundings.

The sound of drumming for traditional Taiko drumming and lion dance

Drumming is an important part of traditional performances in different cultures around the world. Taiko drumming, the drumming with lion dance and the related instruments for traditional cultural performances, can produce sounds loud enough to potentially damage the hearing. In this study the sound track and the sound levels of a typical Taiko performance in Hiroshima, traditional lion dance performances with drumming and other accompanying musical instruments in a school and a shopping mall in Singapore, as well as a traditional drumming performance in a school concert hall were recorded and analyzed to assess the potential sound exposure. For both lion dance performances, the A-weighted equivalent sound pressure level with slow time response (LASeq) was found to be below 87dBA and a half an hour performance was not likely to infringe the The National Institute for Occupational Safety and Health (NIOSH) standard. On the other hand, the half an hour of Taiko drumming performance may hit the recommended exposure level (REL) from NIOSH with LASeq of 97dBA. Both the Taiko drumming and lion dance performances were found to have significant low frequency content with the C-weighted sound levels higher than the corresponding A-weighted sound levels. The idea of using a calibrated smartphone for assessing the sound levels of drumming and traditional lion dance performance is that it can be carried out at any time and any location with the encountering of a drumming performance without the need for pre-preparation of sound measurement equipment.

Traffic Noise Modelling Using Land Use Regression Model Based on Machine Learning, Statistical Regression and GIS

This study estimates the equivalent continuous sound pressure level (Leq) during peak daily periods (‘rush hour’) along the New Klang Valley Expressway (NKVE) in Shah Alam, Malaysia, using a land use regression (LUR) model based on machine learning, statistical regression, and geographical information systems (GIS). The research utilises two types of soft computing methods including machine learning (i.e., decision tree, random frost algorithms) and statistical regression (i.e., linear regression, support vector regression algorithms) to determine the best approach to create a prediction Leq map at the NKVE in Shah Alam, Malaysia. The selection of the best algorithm is accomplished by considering correlation, correlation coefficient, mean-absolute-error, mean-square-error, root-mean-square-error, and mean absolute percentage error. Traffic noise level was monitored using three sound level meters (TES 52A), and a traffic tally was done to analyse the traffic flow. Wind speed was gauged using a wind speed meter. The study relied on a variety of noise predictors including wind speed, digital elevation model, land use type (specifically, if it was residential, industrial, or natural reserve), residential density, road type (expressway, primary, and secondary) and traffic noise average (Leq). The above parameters were fed as inputs into the LUR model. Additional noise influencing factors such as traffic lights, intersections, road toll gates, gas stations, and public transportation infrastructures (bus stop and bus line) are also considered in this study. The models utilised parameters derived from LiDAR (Light Detection and Ranging) data, and various GIS (Geographical Information Systems) layers were extracted to produce the prediction maps. The results highlighted the superior performances by the machine learning (random forest) models compared to the statistical regression-based models.

Temporal integration of partial loudness of helicopter-like sounds

When developing new vehicles that are to be operated in existing background noise, such as electric vertical take-off and landing aircraft (eVTOLs) in cities, a sound design goal should be to minimize the loudness in the given background noise. Rotorcraft sounds are characterised by their pulses, and the choice of rotor size and number allows to vary the temporal characteristics. We asked participants to compare the loudness of pulse trains with pulse durations of 1, 2, 5, 10 and 20 ms and a pulse rate of 20 Hz in a two-interval, two-alternatives forced choice task and a 1-up/1-down procedure. Street noise was presented simultaneously with the pulse trains, and had the same root-mean-square (RMS) level as the fixed reference pulse train of about 65 dB SPL. First results indicate that the sounds with a short pulse duration need considerably less RMS level to result in the same loudness as a long pulse duration, i.e. the partial loudness of shorter pulses is higher at the same equivalent sound pressure level.

Psycho-physiological evaluations of low-level impulsive sounds produced by air conditioners

Air conditioners are widely used in buildings to maintain thermal comfort for long time. Air conditioners produce sounds during operation, and air conditioners are regarded as one of the main noise sources in buildings. Most sounds produced by the air conditioner do not fluctuate over time and sound quality of the steady sounds produced by the air conditioner have been evaluated. However, air conditioners sometimes produce low-level and impulsive sounds. Customers criticizes such sounds are annoying when they sleep and they spend time quietly in the living room. The aim of this study was to determine the factors that significantly influence the psycho-physiological response to the low-level impulsive sounds produced by air conditioners. We assessed the A-weighted equivalent continuous sound pressure level (LAeq) and factors extracted from the autocorrelation function (ACF). Subjective loudness, sharpness, annoyance, and electroencephalography (EEG) were evaluated. Multiple regression analyses were performed using a linear combination of LAeq, the ACF factors, and their standard deviations. The results indicated that LAeq, the delay time of the first maximum peak, the width of the first decay of the ACF, and the magnitude and width of the IACF could predict psycho-physiological responses to air conditioner sounds.

Acoustic Barriers to Reduce Sound Pressure and Environmental Noise in the Ica Fencing

The objective was to determine the reduction of sound pressure through acoustic barriers, knowing the factors that affect the propagation of its acoustic emission, the methodology was the quantitative design, explanatory level, pre-experimental type, pre and post-test, based on studies of behaviors of other barriers such as noise mitigating measures; Two sound level meters were used to measure noise, one of which served as a reference since the sound spectrum due to traffic has a varied behavior. The results obtained in the tests carried out in the field and office work, allowed us to corroborate the Equivalent Continuous Sound Pressure Level (LAeqT). We conclude that Calle Lima 1ra. block and 1st. block Av. Grau, exceeds the standard limits established in the S.D.N ° 085-2003-PCM Words.

Application of loudness level to temporally varying sounds

Most of the environmental noises are temporally varying and include various frequency components. Various methods for evaluating the environmental noises have been proposed. Among them, the method for calculating loudness level was first standardized in 1975 as ISO 532, including Stevens' and Zwicker's methods. Unfortunately, these methods can only be applied to steady state sounds. On the other hand, Aeq (Equivalent Continuous A-weight Sound Pressure Level) is standardized for the evaluation of level fluctuating environmental sounds as ISO 1996. In , the energy mean and A-weighting are used for averaging temporal fluctuation and frequency weighting, respectively. The present authors with their colleagues have conducted many psychological experiments using artificial sounds and actual sounds since 1970's and have being introduced that p (Loudness-based Method), which is a combination of ISO 532 for frequency weighting and ISO 1996 for temporal level fluctuation, is a good method for evaluating various kinds of environmental sounds. ISO 532-1 (Zwicker's method) has been revised including the temporal fluctuation into consideration in 2017, in which p has been adopted as a note. The merit of p will be introduced in this paper presenting many examples.

Compensating for missing data in the OHRKAN cohort study examining total leisure noise exposure among adolescents

Objective Investigating determinants of total leisure noise (TLN) exposure among adolescents over 7.5 years and compensating for missing data due to loss to follow-up. Design In the OHRKAN cohort study, data were collected by questionnaires at four waves. TLN was calculated from self-reported duration spent participating in 18 leisure activities. High exposure was defined as exceeding 85 dB(A) of equivalent continuous average sound pressure level (SPL) during a 40-h week. Multiple imputation (MI) and generalised estimating equations (GEE) were used to analyse odds ratios (OR) of determinants of TLN exposure and compared to complete-case analysis. Study sample Closed cohort of 2148 students enrolled in grade 9 of any school in Regensburg (Germany), recruited from 2009 to 2011. Results Up to 74% of adolescents had risky TLN exposure, depending on wave. The most significant sources were discotheques, portable listening devices (PLD) and stereo systems. Higher TLN exposure was associated with time point, education, single-parent households and gender. MI under MAR assumption changed results only slightly compared to complete-case analysis. Conclusions Prevalence of risky TLN is high during adolescence. MI reinforced trends detected in former results of OHRKAN. Preventive measures should consider the main drivers of noise exposure including changes by age and high risks groups.

Evaluation of sound levels in elective orthopaedic theatres during primary hip and knee arthroplasty

BackgroundOrthopaedic surgery involves tools which could cause noise-induced hearing loss in theatre staff. Threshold levels for occupational noise exposure have been developed in the U.K., above which action is required to reduce exposure. The aims of our study were to determine whether equivalent continuous sound pressure levels during elective arthroplasty can be measured using readily available materials, and to assess whether noise exposure levels stand within acceptable occupational noise exposure levels. Materials and methodsSound pressure levels of orthopaedic saws were recorded using the MicW i436 connected to an iPhone 4S and the iOS SoundMeter application, and using a professional sound meter.Equivalent sound pressure levels were recorded for total hip replacement (THR) and total knee replacement (TKR) using the MicW i436 SoundMeter application. Data obtained was then used to calculate a “worst case” daily exposure value to assess if sound levels were compliant with U.K. guidelines. ResultsSound pressure levels recorded using the MicW i436 and Soundmeter application were accurate compared to professional soundmeter readings. THR showed equivalent sound pressure levels (LAeq) of 77 dBA and TKR showed a LAeq of 80 db. Calculated “worst case” scenarios for daily noise exposure using these values did not meet the lower exposure action values set out by U.K. guidelines. ConclusionsIt is possible to accurately measure continuous sound pressure levels during elective orthopaedic surgery using readily available materials. Noise exposure values during TKR meet lower exposure action values, and when “worst case” daily exposure levels are calculated this level is still lower than the threshold.

Application of Machine Learning to Include Honking Effect in Vehicular Traffic Noise Prediction

A vehicular road traffic noise prediction methodology based on machine learning techniques has been presented. The road traffic parameters that have been considered are traffic volume, percentage of heavy vehicles, honking occurrences and the equivalent continuous sound pressure level. Leq A method to include the honking effect in the traffic noise prediction has been illustrated. The techniques that have been used for the prediction of traffic noise are decision trees, random forests, generalized linear models and artificial neural networks. The results obtained by using these methods have been compared on the basis of mean square error, correlation coefficient, coefficient of determination and accuracy. It has been observed that honking is an important parameter and contributes to the overall traffic noise, especially in congested Indian road traffic conditions. The effects of honking noise on the human health cannot be ignored and it should be included as a parameter in the future traffic noise prediction models.

The long-term effects of exposure to noise on the levels of thyroid hormones: A four-year repeated measures study

Animal studies have suggested that noise exposure can be associated with changes in the levels of thyroid hormones. However, no evidence is available that quantified this effect on humans. This study aimed to quantify the long-term effects of exposure to noise and its different frequencies on thyroid hormone levels. A four-year repeated measures study was performed among male workers of a thermal power plant industry from 2016 to 2020. Overall, 1032 observations were examined. To determine exposure to noise for each participant, the 8-hour equivalent sound pressure levels (Leq) were measured at weighting channels of Z, A, and C for an octave-band including low (31.5, 63, 125 Hz), middle (250,500, and 1000 Hz), and high (2, 4, 8 kHz) frequency noises. The fasting blood samples were also taken to determine thyroid hormone levels (TSH, Thyroid-stimulating hormone; T4, Thyroxine; T3, Triiodothyronine). The mixed-effects linear regression was applied to specify the percent changes in the levels of thyroid hormones. The prevent changes (95% confidence interval) of T4, T3, and TSH levels per a 10-dB increase in Leq based on the full adjusted model were estimated −0.90 (−1.68, −0.11), −0.70 (−1.44, 0.05), and 3.94 (0.58, 7.40), respectively. The highest percent changes in the T4 and TSH hormones were identified at 500 Hz (percent change = −1.08 and 95% CI = −1.93, −0.23) and with little difference at 1 (percent change = 4.73 and 95% CI = 0.91, 8.70) and 2 kHz (percent change = 4.72 and 95% CI = 1.13, 8.52) frequencies, correspondingly. Our findings indicated that long-term noise exposure may be associated with changes in the levels of thyroid hormones. Although more studies are warranted, noise-induced thyroid dysfunction may play a significant role in the biological pathways of the effects of noise on the human body.

Occupational Hearing Loss Associated With Non-Gaussian Noise: A Systematic Review and Meta-analysis.

Epidemiological characteristics of occupational noise-induced hearing loss (NIHL) associated with non-Gaussian noise are still unclear and have been rarely reported in the literature. The relationships between non-Gaussian noise exposure and occupational NIHL were analyzed based on the published papers. Systematic review and meta-analysis of epidemiological studies were performed. Of 78 epidemiological studies (47,814 workers) selected, there were seven cohort studies and 71 cross-sectional studies. The incidence of high-frequency NIHL (HFNIHL) and speech-frequency NIHL (SFNIHL) in the seven cohort studies was 10.9 and 2.9%, respectively. In 71 cross-sectional studies, the prevalence of HFNIHL and SFNIHL was 34.2 and 18.9%, respectively. The average hearing threshold level at the high frequencies was 42.1 ± 17.4 dB HL. Workers exposed to non-Gaussian noise had a higher risk of developing HFNIHL than those not exposed to noise (overall-weighted odds ratio [OR] = 4.46) or those exposed to Gaussian noise (overall-weighted OR = 2.20). The Chi-square trend test demonstrated that the prevalence of HFNIHL was positively correlated with age, cumulative noise exposure, and exposure duration (p < 0.001). Workers exposed to non-Gaussian noise suffered from greater NIHL than those exposed to Gaussian noise or not exposed to noise. Age, exposure duration, noise level, and noise temporal structure were the main risk factors for occupational NIHL. The A-weighted equivalent continuous sound pressure level (LAeq) is not a sufficient measurement metric for quantifying non-Gaussian noise exposure, and a combination of kurtosis and noise energy metrics (e.g., LAeq) should be used. It is necessary to reduce the exposure of non-Gaussian noise to protect the hearing health of workers.

Multidimensional Psychological Evaluation of Air Conditioner Sounds and Prediction via Correlation Parameters

Air conditioners are regarded as a major source of noise in built environments. Although noise control technology has reduced the sound produced by air conditioners to a comparatively low level, some people may still feel that certain aspects of the sound quality lead to discomfort. Indeed, both the sound level and the sound quality of an air conditioner can affect user’s acoustic comfort. The aim of this study was to determine the factors that significantly influence the subjective response to the sound of air conditioners. We assessed the A-weighted equivalent continuous sound pressure level (LAeq) and factors extracted from the autocorrelation function (ACF) and interaural cross-correlation (IACF). Subjective loudness, sharpness, and annoyance were evaluated using a paired comparison method. Multiple regression analyses were performed using a linear combination of LAeq, the ACF factors, IACF factors, and assessment of their standard deviations. The multiple regression analyses indicated that LAeq, the delay time of the first maximum peak, the width of the first decay of the ACF, and the magnitude and width of the IACF could predict subjective responses to air conditioner sounds.

Analysis of Noise Level and Sound Transmission Loss (STL) of Noise Barrier Material for the Construction Site

The construction activities are commonly known as the noisy and annoying work that affects a human’s routine. Those students and lecturers whose location are at the noise receptor locations might be suffering from the health impairment. The objective of this study is to assess and determine the noise level present throughout the daytime period (9AM - 12PM and 2PM - 5PM) at respective measurement points. The analysis of noise spectrum of the sound source from 125 Hz to 4 kHz is part of the scope of study as well. The analysis was carried out by comparing the recommended safe noise level with the equivalent continuous sound level (LAeq) and sound pressure level (Lp) gathered from this study. By setting up a barrier to shield or enclose the sound source is the common way to control the noise transmission. Therefore, selection of the best noise barrier materials is based on the sound transmission loss (STL) value. In this study, the experiment STL of four different types of noise barrier material (newspaper, aluminium foil, cotton and EPS foam) also was carried out in the small scale of reverberation chambers equipped with the LMS Test Lab and LMS SCADAS Mobile device. The 16 tested one-third octave frequency band ranging from 125 Hz to 4 kHz had been utilized in this study. The results revealed that the material of newspaper produced the STL ranging from 0 dB to 9.7 dB within the low frequency of 125 Hz to 800 Hz. Meanwhile, the aluminium foil, had the optimum performance with at least 5.4 dB and above for the STL value at higher frequency ranging from 1 kHz to 4 kHz. Generally, the newspaper is considered as the best noise barrier material as it able to reduce the noise level more throughout the selected frequency range in this study.

Noise Exposure Levels in Black Tea Processing Factories and Its Effects on Employees

The aim of this study was to determine the daily noise exposure levels in black tea processing factories and to evaluate its effects on employees' occupational health and safety. In the study, the sound pressure level dBA values were measured at the ear levels of the employees in each production unit in three tea factories operating in Artvin Province. These factories where the measurements were made consist of withering, curling, oxidation, drying (boiler and stove) and classification units. These units include various systems and mechanisms formed by conveyors, fans, steam heaters, boilers, reducers, pallets, hoods, screens, gears, and drums. In the measurements performed considering the ISO 9612:2009 (Acoustics Determination of Occupational Noise Exposure Engineering Method) standard, a sound pressure level meter in Type-2 class complying with the requirements of the IEC 61672-1: 2002 was used. A weighted equivalent sound pressure levels were determined using the measured values. Considering these values and working times, personal daily noise exposure levels were calculated. It was determined that the equivalent sound pressure levels and daily personal noise exposure levels at the employee ear level were in the range of 77-87 dBA and 74-83 dBA, respectively. Curling units have the highest equivalent sound pressure level (86.81 dBA) and daily personal noise exposure level value (83.10 dBA) compared to other units, while boilers have the lowest equivalent sound pressure level (76.75 dBA) and daily personal noise exposure level value (73.55 dBA). Considering the regulation on protection of employees from noise related risks, it was concluded that the daily noise exposure level reached the lower exposure action value (80 dBA) in these factories. The study showed that the health and work efficiency of the employees could be adversely affected by noise in tea factories, considering various research results and Regulations on noise.

Assessment of Community Noise Annoyance due to Transverse Rumble Strips Installation at Residential Areas

Transverse rumble strips (TRS) acts as a traffic calming device to alert inattentive drivers, however, inappropriate design may generate excessive noise level which cause annoyance among the nearby residents. This study attempts to assess community noise annoyance by investigating current TRS designs and characteristics, measuring roadside noise level and traffic characteristics and evaluating noise annoyance due to TRS installation. Middle overlapped (MO), middle layer overlapped (MLO) and raised rumbler (RR) TRS profile types were selected. Noise indices such as A-weighted equivalent continuous sound pressure level (LAeq), sound level exceeding 10% (L10) and 90% (L90) of specified time were measured using sound level meter (SLM) based on ISO 11819 - 1: 2001 Acoustics: Measurement of the influence of road surfaces on traffic noise - Part 1: statistical pass-by (SPB) method. Traffic characteristics such as volume and speed were also measured. Then, community noise annoyance was evaluated in terms of LAeq changes, noise limit comparison by the Department of Environment (DOE) and traffic noise index (TNI) calculation. It was found that there are various TRS profile types with the thickness of only 3mm. Regardless the types, TRS installation has increased the roadside noise level of about 7dBA and exceeded permissible noise limits.

Short-Term Annoyance Due to Night-Time Road, Railway, and Air Traffic Noise: Role of the Noise Source, the Acoustical Metric, and Non-Acoustical Factors.

Field studies on traffic noise-induced annoyance have predominantly used estimated outside noise levels. We intended to complement existing knowledge with exposure–response relationships that are based on precise indoor noise measurements. Acoustic recordings inside the bedrooms of nightly road traffic and annoyance ratings in the following morning were obtained from 40 suburban residents (mean age 29.1 years ± 11.7; 26 females). We derived exposure–response functions for the probability to be “annoyed at least a little” (%LA). Further analyses compared data from the current study with those from two earlier studies on railway and aircraft noise. Annoyance increased with the number of traffic events and the equivalent sound pressure level. The inclusion of non-acoustical factors (such as assessment of road transport) improved the prediction considerably. When comparing the different traffic noise sources, %LA was higher for road than for air traffic at a given LAeq,night, but higher for road and railway than for air traffic at a given number of noise events. Acoustical as well as non-acoustical factors impact short-term annoyance induced by road, railway, and air traffic. Annoyance varies across noise sources, which may be due to differences in acoustical characteristics or in the temporal noise distribution throughout the night.

Impact of the COVID-19 Lockdown Measures on Noise Levels in Urban Areas-A Pre/during Comparison of Long-Term Sound Pressure Measurements in the Ruhr Area, Germany.

Background: A major source of noise pollution is traffic. In Germany, the SARS-CoV-2 lockdown caused a substantial decrease in mobility, possibly affecting noise levels. The aim is to analyze the effects of the lockdown measures on noise levels in the densely populated Ruhr Area. We focus on the analysis of noise levels before and during lockdown considering different land use types, weekdays, and time of day. Methods: We used data from 22 automatic sound devices of the SALVE (Acoustic Quality and Health in Urban Environments) project, running since 2019 in Bochum, Germany. We performed a pre/during lockdown comparison of A-weighted equivalent continuous sound pressure levels. The study period includes five weeks before and five weeks during the SARS-CoV-2 induced administrative lockdown measures starting on 16 March 2020. We stratified our data by land use category (LUC), days of the week, and daytime. Results: We observed highest noise levels pre-lockdown in the ‘main street’ and ‘commercial areas’ (68.4 ± 6.7 dB resp. 61.0 ± 8.0 dB), while in ‘urban forests’ they were lowest (50.9 ± 6.6 dB). A distinct mean overall noise reduction of 5.1 dB took place, with noise reductions occurring in each LUC. However, the magnitude of noise levels differed considerably between the categories. Weakest noise reductions were found in the ‘main street’ (3.9 dB), and strongest in the ‘urban forest’, ‘green space’, and ‘residential area’ (5.9 dB each). Conclusions: Our results are in line with studies from European cities. Strikingly, all studies report noise reductions of about 5 dB. Aiming at a transformation to a health-promoting urban mobility can be a promising approach to mitigating health risks of noise in cities. Overall, the experiences currently generated by the pandemic offer data for best practices and policies for the development of healthy urban transportation—the effects of a lower traffic and more tranquil world were experienced firsthand by people during this time.

Louvred Noise Barrier for Traffic Noise Reduction

Environmental issues near roads become more and more important in our society daily life. One of the most critical environmental issues is traffic noise. The present paper study louvred noise barrier designed by authors. The louvred noise barrier provides sound attenuation while allowing airflow and sunlight through it. Since the airflow resistance of the barrier is low, it requires a shallow foundation compared to conventional noise barriers. The sound attenuation performance of the louvred noise barrier was tested experimentally in a sound transmission chamber. Airflow resistance simulated using a computational fluid dynamics model. The simulation and experimental study were done with different louvred noise barrier setup: change of louvre blade angle and sound-absorbing material thickness. The results showed potential for future development for the field testing. Sound attenuation was highest in 2500 Hz and 3150 Hz octave frequency bands. Depending on the louvred barrier setup, sound attenuation was up to 28 dB(A) in mentioned frequency bands. The equivalent sound pressure level reduced up to 17 dB(A). The results showed that an increase in the louvre blade angle increases sound attenuation and increases airflow resistance.