Sound Pressure Level Values Research Articles

Numerical investigation of geometrical parameters on the hydrodynamic noise characteristics of submerged bodies and comparisons with experiments

The effects of the geometrical parameters on the hydroacoustic characteristics of the flow over rectangular, square and circular cylinders are investigated by numerical analyses and experiments. The numerical simulations are carried out by using a hybrid method which combines RANS with FWH equation. In order to validate the numerical results, the hydroacoustic measurements are also performed for the circular cylinders. The circular cylinders with diameters of 9.5, 19.0, 38.0 and 65.0 mm and aspect ratios of 2.5, 5.0 and 10.0 are employed for the hydroacoustic measurements and analyses. The rectangular cylinders with side ratios of 0.3, 0.6, 1.8 and 3.0, and also square cylinder with the side ratio of 1.0 are considered in hydroacoustic analyses. The Reynolds numbers are in the range of 2.25 × 104 and 1.7 × 105. The hydroacoustic characteristics of the cylinders are obtained to be completely different due to the differences in the shear layer separation, reattachment mechanism and the intensity of disturbance. The shape of the noise spectrum significantly changes with the geometrical shapes of the cylinders. The spectrum becomes narrower by an increase in the side ratio. The main peak frequency reduces when the side ratio increases. The highest value of the maximum sound pressure level, SPLmax are observed for the square cylinder and the lowest value for the rectangular cylinder with the side ratio of 0.6. The peak spectrum becomes like a line spectrum as the cylinder diameter decreases. The main peak frequency decreases when the cylinder diameter increases but it is almost constant with the aspect ratio. At the constant Reynolds number, the broadband noise level and SPLmax decrease with an increase in the cylinder diameter and decrease in the aspect ratio. A good agreement between the numerical and experimental results are obtained.

Acoustic Characteristics of Vocal Sounds Used by Professional Actors Performing Classical Material Without Microphones in Outdoor Theatre

Theatre actors use voice in virtually any physical position, moving or still, and perform in a wide range of venues. The present study investigated acoustic qualities required to perform classical material without electronic amplification in outdoor spaces. Eight professional actors, four female, four male, from NY Classical Theatre performed one-minute monologues, first stationary, then moving, for audio recording in Central Park. Four subjects recorded two monologues each, from productions in which they played both male and female characters. Data were analyzed for fundamental frequency (F0), sound pressure level (SPL), and long-term average spectrum (LTAS). Overall, F0 ranged between 75.38 and 530.33 Hz. Average F0 was 326 Hz stationary and 335.78 Hz moving for females, 248.54 Hz stationary, 252.82 Hz moving for males. SPL ranged from 28.54 to 110.51 dB for females, and 56.69 to 124.44 dB for males. Average SPL was 82 dB for females, 96.98 dB for males. On LTAS, females had a peak between 3 and 4 kHz ranging from 1.5 to 4.5 dB and another between 4 and 5 kHz ranging from 2 to 4.5 dB, while males had a peak between 3 and 4 kHz ranging from 1 to 8.5 dB. Actors appear to use a similar F0 range across gender and performing conditions. Average F0 increased from stationary to moving. Males had greater SPL values than females, and the amplitude of peaks in the region of the Actor's Formant of LTAS curves was higher in male than female voices.

Acoustic analysis of a single-cylinder diesel engine using magnetized biodiesel-diesel fuel blends

Fuels have important effects on the quality parameters of engines such as noise pollution and vibration. Diesel fuel are used in wide range of applications especially in compression ignition engines. The objective of the present research is evaluation of the noise emitted from a single-cylinder diesel engine using magnetized biodiesel-diesel fuel blends. In general, samples were provided with different percentages of the biodiesel-diesel blends as diesel (100, 95, 90, and 80%) and biodiesel (0, 5, 10, and 20%) by applying magnetic field (0, 5300 and 7000 G) to fuel line known as DxByMz. The measurements were done on a power tiller engine at a 10 cm distance from driver ear with three replications. The statistical approach in time domain and signal processing in frequency domain were applied for data analysis. The results of the variance analysis approved significant differences between the studied fuel blends and magnetic levels at 1% probability level. The highest and lowest average value of sound pressure level was corresponded to D100B0M0 and D80B20M5300, respectively. The results in frequency domain showed that the maximum sound pressure level values were in the frequency range of 31.5–200 Hz for all fuel blends and magnetic levels. The frequencies related to the maximum sound values varied by changing biodiesel percent and magnetic level.

The Feasibility of a Neck-Surface Accelerometer for Estimating the Amount of Acoustic Output During Phonation Regardless of the Difference in the Mouth Configuration

This study aimed to assess the feasibility of a neck-surface accelerometer (ACC) for estimating the amount of acoustic output produced during phonation regardless of individual differences or the mouth configuration. The sound pressure levels (SPL) and signals of a neck-surface ACC were simultaneously recorded, while each of healthy nondysphonic speakers was asked to perform the following phonatory tasks: (1) repetitive phonation of the vowel /e:/ at various loudness levels; (2) gradually increasing vocal loudness (crescendo) during sustained phonation of the vowel /e:/; (3) repetitive smooth transition between phonation of the vowel /a:/ and /u:/ with the same vocal effort or between phonation of the vowel /e:/ and production of a hum /m:/. The skin acceleration levels (SAL) were calculated from the ACC signals. Although the correlations between the SPL and SAL values were nearly linear in both repetitive-vowel-phonation and vowel-crescendo tasks, the crescendo task showed a higher correlation within individuals than the repetitive task, but with substantial individual differences. The correlation between the increments in the SPL and SAL was higher than that between the SPL and SAL. In the smooth-transition tasks, the SAL-but not the SPL-showed no significant differences between the vowels or hum. These results show that the signal intensity of a neck-surface ACC reflects the amount of acoustic output during phonation irrespective of the mouth configuration, but shows nonnegligible individual differences. The use of the increment in the SAL is suggested to be suitable for comparing the amount of acoustic output.

Avaliação de ruído ambiental da região central da cidade de Uberaba – MG

A poluição sonora ocorre quando um som ultrapassa o limite auditivo normal. Segundo a Organização Mundial de Saúde (OMS) a poluição sonora é a segunda maior causa de poluição, sendo considerada um problema de saúde pública mundial, pois afeta a saúde física e mental da população. É uma das fontes de poluição que mais geram incômodos atualmente em decorrência dos excessivos ruídos gerados por diferentes fontes. Devido aos diversos problemas de saúde acarretados pela poluição sonora o objetivo do estudo foi avaliar alguns pontos da região central de Uberaba – MG a fim de quantificar os níveis de intensidade sonora existentes e verificar se os níveis de ruído encontram-se acima do permitido causando efeitos negativos nos seres humanos. Foram realizadas medições de nível de pressão sonora de acordo com a NBR 10.151/2019 em 5 zonas da região central de Uberaba e em cada zona foram realizados 4 pontos de medição. Para cada ponto, a medição foi realizada de 1 em 1 minuto, totalizando 10 minutos. A partir dos valores de níveis de pressão sonora foi obtido o nível de pressão sonora equivalente que corresponde à média do ruído de cada local e este valor foi comparado com as normas referentes a poluição sonora. Os resultados obtidos ficaram acima dos estabelecidos por normas podendo acarretar danos à saúde da população que está submetida a esta poluição. Desta forma é necessário um melhor planejamento urbano da cidade e a incorporação de medidas de controle e de atenuação sonora para o bem-estar da comunidade. Palavras-chave: Ruídos. Poluição sonora. Danos à saúde.

Impact noise of prostate biopsy devices

Objective: To analyse the impact noise generated by prostate biopsy devices.Materials and methods: In a laboratory setting, repeated impact noise was recorded at distances of 50 cm and 100 cm using five brands of device on chicken meat, an apple and an empty target. In a clinical setting, the impact noise levels of prostate biopsy devices were recorded in 40 real patient cases using three brands of device.Results: In the laboratory setting, the average SPL (sound pressure level) peak level ranged from 104.3 to 121.3 dB. The highest impact noise levels were measured with the Monopty device, ranging from 114.8 to 122.4 dB. In the clinical setting, there were no statistical differences between repeated SPL values for each specific target. Also, the noise levels were equal when the same device brand was used at 50 cm and 100 cm. The highest SPLs were recorded with the Monopty device, which ranged from 110 to 127 dB. The corresponding values for the Max-Core and Multicore were from 106 to 122.5 dB and from 108 to 116.5 dB, respectively.Conclusions: Biopsy devices generate high peak levels of impact noise. Personnel performing biopsies are advised to consider using hearing protection, even though the impact noise may not induce permanent hearing loss.

Song amplitude and population density in two sympatric warblers, Phylloscopus schwarzi and P. fuscatus

ABSTRACT In passerine birds, song is widely used broadcasting signal. One song trait that so far has received little attention is amplitude, i.e. the sound pressure level of a song. It has been shown that there is a considerable variation in song amplitude between species, but the causes and consequences of this variation are poorly studied. Here, we measured song amplitude in two similar-sized sympatric Phylloscopus, Radde’s Warbler P. schwarzi and Dusky Warbler P. fuscatus. We found that Radde’s Warbler males sing much more loudly than males of Dusky Warbler. The sound pressure level values of songs of Radde’s and Dusky Warblers were 78.6 ± 2.4 dB(A) (n = 16 males) and 70.9 ± 1.5 dB(A) (n = 16) at a distance of 1 m, respectively. The analysis of video-recordings revealed the larger extension of the neck region (‘throat sac’) in Radde’s Warbler than in Dusky Warbler. We hypothesised that the larger maximum ‘throat sac’ volume might be responsible for the louder song of Radde’s Warbler. We also found that Dusky Warbler males settled twice as close to each other than Radde’s Warblers. We hypothesised that the louder song of Radde’s Warbler could be useful for males of this species given their need to communicate through a larger distance.

“Gear fault Types and Condition Monitoring Indicators for Gearbox” – A Combined Assessment

Lot of research is going in area of condition monitoring and fault diagnosis of gearboxes. Also it has been witnessed that there is no paper which combines the information about gear faults of gearbox and faults identification clues, condition monitoring statistical indicators. In order to develop new condition monitoring indicators, the information of gear faults is important. The condition indicators provide particular information regarding the health of machine or machine components. The intent of this paper is to assess and summarize literature to give a noble reference for firsthand researchers in the area of condition based monitoring of gearbox and in this way to enhance the research in gearbox development. The experiment shows, at 1100 rpm speed and at healthy gear pair the value of Equivalent sound pressure level is 87.4 db. Maximum equivalent sound pressure level is 92.1 db for faulty condition.

Vocal Loudness Variation With Spectral Slope.

Objective This investigation addresses the loudness variations in sones achievable with spectral slope variations (higher harmonic energy) in human vocalization and compares it to the sound pressure level (SPL) variations typically reported in the voice range profile (VRP). Method The primary methodology was computational. The ISO standard 226 was used to convert SPL values to sones for a 125- to 1000-Hz range of fundamental frequency and a -3 dB/octave to -12 dB/octave range of spectral slope. In addition, a retrospective analysis of human subjects' VRPs was conducted, and the experimental results were compared to the theoretical results. Results A very small range of SPL variation (less than 5 dB) in the VRP can produce a large range of loudness. The sensitivity can be on the order of 4 sones per dB SPL change. Conclusion For vocalization in the modal register, loudness variation is not well described by SPL change in dB, especially at high fundamental frequencies where the SPL range in the VRP becomes very small but sizeable loudness variations are still possible.

Frequencies Rotation at High Sound Pressure Levels Toward Low Frequencies

Today, analyzing of sound pressure level and frequency is considered as an important index in human society. Sound experts believe that analyzing of these parameters can help us to better understanding of work environments. Sound measurements and frequency analysis did to fix the harmful frequency in all sections in Shiraz gas power plant with sound analyzer model BSWA 308. The sound pressure levels (LP) and the one and one-third octave band were continuously measured in A and C weighting networks and slow mode for time response. Excel 2013 and Minitab 18.1 software used for statistical calculations. Results analyzed by Minitab 18.1 software. The highest harmful frequency in Shiraz Gas Power Plant (SGPP) was 50 Hz with 115 dB. The sound pressure level (SPL) ranged from 45 dB to 120 dB in one-third octave band and weighting network C. The maximum sound pressure level was in Craft electricity generator with 105.3 dB and 67 Hz. Sound pressure level in surrounded environment was 120 dB. According to the results, in this industry the sound pressure level exceeded the Occupational Exposure Level of Iran (OEL). The value of sound pressure level were higher than the Standard of occupational health. SGPP consumes 47000 cubic meters of natural gas per hour to produce 100 MW (Mega Watt) of electricity. It is very high and it is not economical and cost effective. These numbers indicate that the power plant’s efficiency is low. It could be concluded that the noise pollution is an important issue in these industries. Moreover, SGPP produce noise with loss energy. Frequencies rotation at high sound pressure levels toward low frequencies were happened.

Case study: Analysis of the propagation of noise generated by construction equipment

In the construction industry, workers are exposed to several risks, among them is the noise generated by construction equipment. This research had as its objective to evaluate the noise emitted by circular saws and concrete mixers, equipments usually present on construction sites, in order to propose noise control measures. For that purpose, the propagation curves (isoclines) of the sound pressure level (SPL) were measured and analyzed during the operation of three concrete mixers and three circular saws. The sound measurements were conductedwith the type 2 sound level meter, while for air temperature and wind speed a digital thermo-anemometer was used. Contour lines representing the isoclines of SPL were generated, and control measures were proposed. The results show that values of SPL above 85 dB(A) were observed at a maximal distance of 7 m from the source for concrete mixers and 16 m for circular saws. It was also confirmed that the furthest distance that the SPL is greater than 85 dB(A) depends on the number of barriers, screens and masonry walls. In obstacle-free areas, the rate of reduction of sound intensity was 1.26 dB(A) per meter for concrete mixers and 1.47 dB(A) per meter for circular saws. The SPL isoclines should be considered in planning of construction sites and organizing adequate control measures.

Experimental investigation of acoustic agglomeration of diesel engine exhaust particles using new created acoustic chamber

Many researchers have considered air quality degradation due to the emission of fine particles from industrialized and urban areas during recent decades. Recently, the European Parliament has had concerns about ensuring a healthy human environment. Therefore, the experimental and theoretical investigations of the dynamics of fine particulate matter are for determining efficient monitoring and cleaning air from industrially generated air pollutants. These investigations also imply the use of alternate methods that stimulate fine particle agglomeration. One of the methods is the use of acoustics. Many experimental investigations of particles with a diameter between 1 and 10μm have proven that the use of acoustic agglomeration increases the particle size. Then, conventional air filters can be used to collect the larger particles. This process improves the collection efficiency of the particles. Particulate agglomeration chamber consisting of an acoustic field generator and an inner part was created for the test particles of diesel engines (range from 0.3 to 10μm). Modeling of its elements was performed using Comsol multifunctional software. This sound pressure level is enough [1] to lead the acoustic agglomeration process of particles in the measurable range from 0.3 to 10μm. The sound pressure level reach this value (130–140dB) at the acoustic agglomeration zone.Additionally, the theoretical evaluation of the agglomeration time of two sub-micron particles enabled the estimation of efficient agglomeration of particles with sizes between 0.3 and 10μm during the measurement period. A starting value of 136dB of sound pressure level (SPL) was created in the experimental chamber with the turbulence condition, where SPL values were measured by using the Bruel&Kjaer measurement system “Type 9727” with hydrophone 8104. The observation concentrations of diesel engine exhaust particles in the experimental chamber with and without acoustic influence were performed using Particle Concentration Analyzer 4 APC ErgoTouch Pro 2.The results of experimental research shows that the acoustic agglomeration effect formed the proper conditions for the agglomeration of particles of all diameters (0.3, 0.5, 1.0, 3.0, 5.0 and 10μm).

Relation between peak value and acoustic damping of sound pressure level of one dimensional sound field partitioned with perforated plates

Relation between peak value and acoustic damping of sound pressure level of one dimensional sound field partitioned with perforated plates

Noise Reduction Mechanisms of an Airfoil with Trailing Edge Serrations at Low Mach Number

Trailing-edge serrations have proven to be valid applications of trailing edge noise mitigation for an airfoil, while the physical noise reduction mechanism has not been adequately studied. We performed simulations employing Large-eddy simulation and the Lighthill–Curle method to reveal the variation in the hydrodynamic field and sound source due to the trailing edge serrations. The grid resolution and computational results were validated against experimental data. The simulation results show that: the trailing edge serrations impede the growth of spanwise vortices and promote the development of streamwise vortices near the trailing edge and the wake; the velocity fluctuations in the vertical cross-section of the streamwise direction near the trailing edge are reduced for the serrated airfoil, thereby obviously reducing the strength of the pressure fluctuations near the trailing edge; and the trailing edge serrations decrease the distribution of the sound source near the trailing edge and reduce the local peak value of sound pressure level in a specific frequency range as well as the overall sound pressure level. Moreover, we observed that, in the flow around the NACA0012 airfoil, the location where the strong sound source distribution begins to appear is in good agreement with the location where the separated boundary layer reattaches. It is therefore effective to reduce trailing edge noise by applying serrations on the upstream of the reattachment point.

Theoretical and experimental investigation of acoustic performance of multi-chamber reactive silencers

The acoustic attenuation and performance analysis for blast flow field inside a silencer is investigated. In this regard, a silencer system is designed to reduce the exhaust noise. The effect of position and the number of the baffles for each design on sound transmission loss have been investigated using theoretical, numerical and experimental studies. Three prototypes are manufactured for the experimental studies. Using the measured results, insertion loss graphics have been obtained. The silencer performances are dependent on the baffle geometry, number and the positions. The experimental results are in a good agreement with the simulation results. It is observed that by considering the same number of baffle numbers but located at various locations, the model which shows the best sound transmission loss performance has also the best insertion loss performance and has the least value of peak sound pressure level.

Noise Source Identification of Automotive Radiator by Using Sound Intensity Mapping Method

Automotive radiator played an essential role as a heat exchanger that exchange the circulated heated coolant inside the engine compartment to return into its ambient temperature. Radiator cooling fan that attached at the back of radiator, is a device that work to regulate the coolant temperature when the heated coolant is passed inside the radiator tubes. It produces external flow of air that passes through the fins and tubes of the radiator. However, this external flow contributes high noise level into the system. In consequence of this risk, a detailed experimental study on noise analysis to identify the location of maximum sound pressure level (SPL) generated by variations of cooling fan speed by using sound intensity mapping method is presented. Ethylene Glycol (EG)-water based was used as working fluid operate with engine temperature range from 80 to 90 °C. The cooling fan speed of radiator cooling fan were varied from 750 to 1250 rpm and the water flowrates were 8.0, 11.0, and 14.0 l/min. The results indicate that the noise level is increasing with the fan speed. However, there is no significance difference of change in coolant flow rate and type of coolant fluids to the noise level. The location of maximum sound pressure level is identified and the higher SPL value most located on the blade trailing edge of the suction surface with highest SPL value of 81 db for 1250 rpm fan speed. The project delivers the reliable input for the engineering practice to reduce automotive radiator noise level.

A novel thermal acoustic device based on vertical graphene film

Graphene is an excellent thermoacoustic material due to its small heat capacity per unit area. However, there is obvious thermal leakage from the substrate which lower the sound emission efficiency. Here, in order to improve the efficiency, vertical graphene has been used as thermoacoustic device. In this paper, the high-quality vertical graphene was prepared by the MPCVD method, and the height of the vertical graphene was about 3.4 μm. Then a thermoacoustic device was fabricated based on vertical graphene. Compared to graphene, the unique structure of vertical graphene makes the device less area to substrate with less thermal leakage and can produce a higher sound pressure level (SPL) per unit area under the same height, the SPL value can reach as high as 60 dB at a measure distance of 0.3 cm with input power of 1.2W. This sound device based on vertical graphene is potential to be used in a wide range of applications.

Analysis of the Acoustically Noise Situation in an Urbanized Area in the Presence of Vehicular and Industrial Noise

Acoustic noise is now becoming one of the important problems of the technosphere. The source of such noise in the streets of large cities is mainly motor transport, as well as industrial enterprises located in the city and construction sites. In the report some results of monitoring of acoustic pollution of the big industrially developed cities (on the example of the city of Murom) are considered. Monitoring is carried out with the help of a combined ecology-meteorological system. The measurement errors due to the standard octave analysis procedure with a control at central weighted frequencies are analyzed. It is shown that the application of the full spectral analysis using the fast Fourier transform allows us to compensate for these errors. The features of the construction of the measuring channel used in the monitoring procedure are considered. Some results of analysis of the spectrum and levels of acoustic noise on the streets of the city at different periods of the day are given. It is shown that in the most heavily loaded areas of the city, combining the activity of traffic flows and the functioning of industrial enterprises, the maximum values of sound pressure level of acoustic noise can reach 100 dB. Both maximum and average values of sound pressure are analyzed from the point of view of their compliance with the current sanitary norms. The conclusion is made that the actual noise levels exceed the maximum permissible levels for open spaces.

Travelers’ exposure to vibrations and noise depending on the type of transport – the results of pilot research

For some time residents of big cities have been encouraged to change their means of transport, that is, to swap passenger cars for public transport vehicles. This is meant to help to reduce the problems associated with heavy traffic and air pollution. The authors of the article decided to check if such a change is also beneficial from the point of view of comfort and health of a person who uses public transport. For this purpose values of vibration acceleration and sound pressure level to which Cracow’s commuters are exposed to have been analyzed, depending on the type of vehicle they choose. In this respect measurements have been carried out for passenger cars, buses and trams. Two vehicle models of each type, significantly different from each other (old and new) have been selected for the tests. The measurements during a few trips in each type of vehicle on a predetermined route have been conducted. This article presents a comparison of measured values of vibroacoustic parameters in the time domain. It attempts to assess vibration and noise parameters, taking into account their impact on the health and comfort of the traveler.

Study on acoustic source characteristics of gas pipeline leakage

The characteristics of acoustic source of gas pipeline leakage determine the accuracy and adaptability of leak detection for gas pipelines based on acoustic method. In order to explore the characteristics of leakage acoustic source of gas pipeline, a physical model of gas pipeline leakage was developed. Initially, generation mechanism of acoustic source of gas pipeline leakage is studied in order to identify the basic principle of leak detection of gas pipeline based on acoustic method. After that, the simulation model is developed according to the basic principle of aeroacoustics, the flow field, and sound source characteristics of the gas pipeline leakage. Then, the experimental platform for the study on acoustic source characteristics of gas pipeline leakage is set up using the basic principle of the leak detection based on acoustic method and simulation results. The characteristics of acoustic source of leakage are obtained through experiments. Finally, the simulation and experimental results of acoustic source of leakage under different operating conditions are compared, and the accuracy of the simulation results is verified, which provides a theoretical basis for the engineering application of leak detection for gas pipeline based on acoustic method. The results show that the acoustic source of gas pipeline leakage is mainly quadrupole source and the leakage acoustic energy is mainly in the range of less than 100 Hz. The mean value of sound pressure level is increased with the pressure in pipeline and the size of leak aperture.