A-weighted Equivalent Continuous Sound Level Research Articles

A study examining the long-term effects of aircraft noise on the surrounding residents before the opening of Long Thanh Airport

Long Thanh Airport (LT) is a new airport scheduled to open in 2025 and serve as the largest aviation hub in Vietnam. The residents are expected to experience adverse health effects from long-term noise exposure once LT begins operation. This study aims to serve as a basis for comparing the impact of environmental changes before and after the opening of LT. This study assesses the health of the residents in ten residential areas under the planned flight paths of LT. Currently, before the new airport operates, environmental noise around LT is primarily caused by traffic noise from nearby roads near the selected houses. The 24-hour A-weighted equivalent continuous sound level (LAeq) at a representative house in each area ranged from 51 to 72 dB. In August 2022, 641 residents were surveyed to assess their health conditions. It was found that traffic noise was the most frequently cited environmental nuisance among the surveyed participants. However, the regression model considers contextual factors, noise exposure, and other factors impacting health and indicates that the health of the residents is associated with factors beyond noise exposure, such as noise sensitivity, mobility, and attitude towards transport modes.

An analytical investigation into noise levels in public health sector neonatal intensive care units in the eThekwini District

Background. Noise is a known environmental stressor in the neonatal intensive care unit (NICU), as it may result in adverse effects on preterm neonates because of the unique vulnerability and physiological immaturity of their central nervous systems. Objective. To investigate noise levels in public sector NICUs in the eThekwini District, KwaZulu-Natal Province, South Africa. Methods. An analytical observational study design with purposive sampling of public sector hospitals was used. Noise was continuously measured with a sound level meter in a central location for 48 hours on 2 consecutive days (Sunday and Monday) in the four NICUs. A sample of noise sources, as well as their frequency of occurrence, was identified through direct observation and a frequency spectrum analysis using one-third octave bands. Data were analysed using descriptive and inferential statistics. Results. This study included one tertiary hospital and three regional hospitals in the eThekwini District. Mean noise levels exceeded international recommendations of an A-weighted equivalent continuous sound level (LAeq) of 45 A-weighted decibel (dBA) and an A-weighted maximum sound level (LAmax) of 65 dBA in all four hospitals. The most frequently occurring sources of noise were staff conversations (30.9%, Hospital A), device alarms (21.0%, Hospital B) and closing metal pedal bins (20.0%, Hospital B). Mean LAeqs >45 BA were found in the mid and high frequencies (250 Hz - 6 300 Hz) in all hospitals, particularly during the afternoon. Conclusion. The findings emphasise the need for continuous noise monitoring, awareness and education among healthcare professionals in the NICU. Future research should expand on existing findings and focus on interventions for noise control in NICUs.

Room Acoustical Parameters as Predictors of Acoustic Comfort in Outdoor Spaces of Housing Complexes.

Room acoustical parameters have frequently been used to evaluate or predict the acoustical performance in rooms. For housing complexes in urban areas with high population density, it is important to improve acoustic performance not solely indoors, but outdoors as well; for example on the balconies or in the yards. This paper investigates to what extent classic room acoustical parameters would be able to predict the perceived acoustic comfort in outdoor spaces (i.e., courtyards) of virtual housing complexes. Individual and combined effects of a series of independent variables (such as facade absorption, sound source, and observer position) on short-term acoustic comfort were investigated in three laboratory experiments. ODEON software was used for virtual inner yard simulation, whereby 2D spatialization was carried out for a playback over five loudspeakers. Moderate facade absorption was found to increase acoustic comfort. Relatively pleasant and relatively unpleasant sounds were associated with comfort and discomfort, respectively. Lower acoustic comfort ratings were observed at receiver positions with high sound pressure levels and/or strong flutter echoes. A further analysis of the results is carried out here with respect to the room acoustical parameters and their ability to predict the acoustic comfort ratings. Speech transmission index (STI), definition (D50), clarity of speech (C50) and music (C80), early decay time (EDT), and lateral energy fraction (LF80) were found to be significantly correlated with acoustic comfort. They were found to be significant predictors of acoustic comfort in a series of linear mixed-effect models. Furthermore, linear mixed-effect models were established with the A-weighted equivalent continuous sound level, LAeq, as a significant predictor of acoustic comfort.

An experimental study to measure the acoustical properties of natural fibers at real case broadband excitations

The acoustical properties such as sound transmission loss (STL) and A-weighted equivalent continuous sound level (LAeq) of natural fibers are measured experimentally in this paper. The acoustical properties are measured for various real case acoustic broadband disturbances such as white noise, pink noise, road traffic noise, train noise, ambulance siren noise, aircraft noise, and construction and machinery noises. The above acoustic excitations are passed through the specimens of natural fiber material in order to measure their acoustical properties. The natural fibers used in this study are banana, coconut coir, hemp, jute and kenaf. It is observed in the experimental investigations that kenaf is the best noise absorbing material. The sound reduction of kenaf varies from 5.67 dB to 7.82 dB. The second best material is jute whose sound reduction varies from 4.5 dB to 6.28 dB. Third best material is hemp whose sound reduction varies from 2.88 dB to 5.51 dB followed by the banana fiber. The coconut coir is found to be the worst noise absorbing material among the five natural fibers considered for experimental investigation.

Acoustical Perceptions of Building Occupants on Indoor Environmental Quality in Naturally-Ventilated Building Façades

Accelerated growth of urban population and motor vehicles has resulted in constant exposure to urban traffic noise that is one of the significant environmental stressors in urban environments. The aim of this research as a preliminary study is to evaluate acoustical perceptions of building occupants on their dwelling satisfaction with outdoor traffic noise through naturally-ventilated glazed building facades in the Seoul metropolitan area. This area has the highest population density among the largest countries of Organization for Economic Co-operation and Development (OECD). First, quantitative data of the A-weighted equivalent continuous sound levels (LAeq) at six sites in the Seoul metropolitan area were analyzed, showing that LAeq exceeded the thresholds of noise level standards, 65 dB(A) for day-time (06:00 AM to 10:00 PM) and 55 dB(A) for night-time (10:00 PM to 06:00 AM) respectively. Second, a questionnaire survey was conducted to find the environmental impacts of urban noise transmission on building occupants’ comfort and their ventilation behaviors. It showed that approximately 87% of building occupants (n = 92) used mechanical ventilation systems rather than window ventilation methods. Eighty-two percent of participants have experienced sick building syndrome (SBS)-related symptoms such as skin irritations or coughs. Thirty-three percent of the respondents were deterred from opening windows for natural ventilation due to outdoor traffic noise transmission, and 49% of respondents complained mostly of poor task productivity. The survey outcomes propose the importance of acoustically-treated ventilation openings in naturally-ventilated glazed building facades for building occupants’ indoor environmental quality in high-noise urban areas.

Conductor Surface Conditions Effects on Audible Noise Spectrum Characteristics of Positive Corona Discharge

Conductor surface conditions of high voltage overhead transmission lines have a large influence on corona characteristics. Both audible noise and corona current is highly depended on the corona discharge characteristics. However, relatively few investigations have previously been made on conductor surface conditions effects on audible noise spectrum characteristics. In the present work, the artificial pollution experiments were carried out to simulate the various surface conditions. At the same time, the audible noise spectra and the corona current of the polluted conductor are recorded. From the analysis of the experiment results, it was found that the audible noise spectra level (>1 kHz) and corona current increased obviously as the relative permittivity grew and the amount of pollution increased. Furthermore, from the results of the long-term statistical measurement about A-weighted equivalent continuous sound level (LAeq) of the polluted conductor, the close correlation between the surface potential gradient and the audible noise spectra were obtained.

공기청정기와 가습기의 소음특성

This study investigated noise characteristics of air cleaners and humidifiers in terms of frequency domains and measurement directions. Noise levels of 31 air cleaners and 36 humidifiers were measured in an anechoic chamber according to the related group standards. As for air cleaners, 5 receiving points of 1 m off from front, rear, left, right and top surfaces of the product were considered. In case of humidifiers, 4 receiving points without the rear position were considered in the same manner as air cleaners. In each case, A-weighted equivalent continuous sound level was measured three times for 1 min. As a results, most of the measured air cleaners and humidifiers showed the highest noise levels at top directions due to the air ventilating location. In case of air cleaners, averaged noise levels of top and rear positions were 49.9 and 48.2 dB(A), respectively, whereas averaged noise level of other positions was all 45.2 dB(A). In case of humidifiers, averaged noise level of top position was 44.1 dB(A) whereas averaged noise levels of other positions were 38.7 to 39.1 dB(A). In addition, high frequency content of 1 kHz and 3.15 kHz to 4 kHz for air cleaners and middle frequency content of 500 Hz to 1.6 kHz for humidifiers showed significant contribution to determination of overall noise levels with correlation coefficient of 0.9 and above.

Investigation of Noise Level and Penetration Rate of Pneumatic Drill vis-à-vis Rock Compressive Strength and Abrasivity

In this paper, detailed studies were carried out to determine the influence of rock properties on the sound level produced during pneumatic drilling. Further, investigation was also carried out on the effect of thrust, air pressure and compressive strength on penetration rate and the sound level produced. For this purpose, a fabricated pneumatic drill set up available in the institute was used. Rock properties, like compressive strength and abrasivity, of various samples collected from the field were determined in the laboratory. Drilling experiments were carried out on ten different rock samples for varying thrust and air pressure values and the corresponding A-weighted equivalent continuous sound levels were measured. It was observed that, very low thrust results in low penetration rate. Even very high thrust does not produce high penetration rate at higher operating air pressures. With increase in thrust beyond the optimum level, the penetration rate starts decreasing and causes the drill bit to ‘stall’. Results of the study show that penetration rate and sound level increases with increase in the thrust level. After reaching the maximum, they start decreasing despite the increase of thrust. The main purpose of the study is to develop a general prediction model and to investigate the relationships between sound level produced during drilling and physical properties such as uniaxial compressive strength and abrasivity of sedimentary rocks. The results were evaluated using the multiple regression analysis taking into account the interaction effects of predictor variables.

Correlation of noise levels and particulate matter concentrations near two major freeways in Los Angeles, California

Near-freeway environments are important from public health and environmental justice perspectives. This study investigated the spatial profile of and correlations between noise levels and particulate matter concentrations near two major freeways in Los Angeles, CA. Five minutes averages of A-weighted equivalent continuous sound level (LeqA), ultrafine particle (UFP) number concentrations, and fine particle (PM2.5) mass concentrations were measured concurrently at increasing distances from the freeways on four streets with or without sound wall. Under upwind conditions, UFP showed relatively low concentrations and no obvious gradient, while LeqA showed decay with increasing distance as it did under downwind conditions. Moderate correlations between LeqA and UFP were observed under downwind conditions on all four streets. The presence of a sound wall changed the linear relationship between LeqA and UFP. These data may be used to study the independent and synergistic health impacts of noise and air pollutants near roadways.

Estimating rock properties using sound levels produced during drilling

An attempt has been made in this paper to experimentally investigate the estimation of rock properties like compressive strength and abrasivity using sound levels produced during drilling. The investigation was carried out on a laboratory scale using small portable pneumatic drilling equipment used in hard rock drilling. For this purpose, a pneumatic drill setup was fabricated for drilling vertical holes. The compressive strength and the abrasivity of various rock samples collected from the field were determined in the laboratory. A set of test conditions were defined for measurement of sound level of the pneumatic drill. Also, with the help of the experimental setup, vertical drilling was carried out on the rock samples for varying thrust and air pressure values and the corresponding A-weighted equivalent continuous sound levels were measured. Results of this study indicate that sound level can be a promising tool in estimating rock properties during drilling.

An experimental investigation of jack hammer drill noise with special emphasis on drilling in rocks of different compressive strengths

An attempt has been made in this paper to investigate the influence on sound level due to drilling in rocks of varying physical properties i.e. compressive strength and abrasivity using jackhammer drill. For this purpose, a jackhammer drill setup was fabricated wherein the thrust applied can be varied while drilling vertical holes. The compressive strength and the abrasivity of various rock samples collected from the field were determined in the laboratory. A set of test conditions were defined for measurement of sound level of the jackhammer drill.Also, with the help of the experimental setup, vertical drilling was carried out on the rock samples for varying thrust and air pressure values and the corresponding A-weighted equivalent continuous sound levels were measured.The results of this study indicate that, increase in thrust increases the sound level at higher midband frequencies in the noise spectrum. The study indicated the sound level near the drill rod to be 0.5 to 1.5 dB, 2.0 to 3.0 dB and 4.0 to 6.0 dB higher relative to that at the drill bit, the exhaust and the operator’s position respectively at an air pressure of 5 kg/cm 2 and 160 N thrust for all the rock samples tested. Both the thrust and air pressure were found to have a significant effect on the sound level produced by jackhammer drill at all the measurement locations. The study further shows that an increase in sound level of the order of 1.5 to 2.5 dB at the operator’s position can occur with an increase in air pressure by 2 kg/cm 2 at 160 N thrust and with an increase in compressive strength and decrease in abrasivity of rocks. Also, the increase in sound level at the operator’s position with increase in compressive strength and decrease in abrasivity of rock is of the order of 1.0 to 2.0 dB. In order to maintain a constant penetration rate in the rocks, both the thrust and air pressure need to be increased with an increase in compressive strength and decrease in rock abrasivity.Therefore,increased compressive strength and lower abrasivity of rocks will require higher air pressure and thrusts to be applied to achieve an optimum penetration rate and therefore will result in higher sound level at the operator’s position and at other measurement locations. © 2007 Institute of Noise Control Engineering.