Determination Of Sound Power Levels Research Articles

Sound power level determination of roads in Tokyo using aerial photographs, machine learning, and ASJ RTN-Model 2018

The traffic noise map is a visual representation of the sound level distribution in and around a road based on the sound power levels of vehicles on the road and the diffraction and reflection by the surrounding buildings. The purpose of creating the traffic noise map is to facilitate the government, researchers, industry, and the public in their efforts to track trends in transportation-related noise. To create noise maps, sound power level determination is the most important. The road traffic noise prediction model "ASJ RTN-Model 2018" has been widely used for road traffic noise prediction in Japan. Provided a method of calculating sound power level by vehicle classification, traveling speed, and driving mode. In the study, to obtain the vehicles' classification and coordinates, YOLO (You Only Look Once) was used to process the aerial photos. This study constructed sound power level distribution on the road network in Tokyo. Additionally, the estimated data were compared with the measured data to confirm the estimated data's reliability.

Modernization of the instrumentation requirements to support ISO noise test standards

ISO TC43/SC1/WG28 develops the basic machinery noise test standards for products and equipment. This includes the determination of sound power levels in the ISO 3740 series and the measurement of operator/bystander sound pressure levels in the ISO 11200 series. The instrumentation requirements for these standards have historically been based on a reference the sound level meter standard, IEC 61672, supplemented by another to IEC 61260 for fractional octave filters. Both IEC standards are fundamentally based on the concept of the measurement system being a packaged sound level meter. Many modern implementations of these standards no longer use a sound level meter. Many now use multi-channel, computerized instrumentation systems and custom software. These systems provide measurement equivalence to the IEC sound level measurement standards. However, they don’t fully comply with all of the requirements in these IEC standards. Many acoustic testing programs have chosen to ignore these non-complianceissues, have implemented systems that are more efficient, lower measurement uncertainty and provide measurement equivalence to IEC 61672 and IEC 61260. As industry has already decided to implement these systems, there is a need to develop modernized instrumentation requirements to support the basic sound power and sound pressure level measurement standards using current technology.

First ideas for a revision of ISO 9614

ISO 9614 describes the determination of sound power levels by the two microphone intensity technique. Despite some physical advantages the method is relatively seldom used. To improve this situation, theoretical and experimental investigations were performed, which focused mainly on the adequacy of the currently standardized indicators and criteria. This paper summarizes these results and develops first ideas for a revision of ISO 9614. One main proposal is to perform measurements generally in the one-third octave bands between 50 Hz and 10 kHz with a 12 mm spacer and to apply appropriate corrections in the highest three one-third octave bands. Furthermore, it is proposed to require additional measurements with a larger spacer at lower frequencies, if the dynamic capability of the instrument is insufficient. The A-weighted sound power level is calculated from the one-third octave band levels, which may have different grades of accuracy. Calculating different A-weighted sound power levels from different sets of frequency bands fulfilling criteria for different grades of accuracy then allows for designating a grade of accuracy to the A-weighted sound power level. This is considered to be a major improvement since the A-weighted sound power level is the main descriptor for the sound emission of sources.

ERROR AND UNCERTAINTY IN NEAR-FIELD SOUND POWER ASSESSMENTS OF INDUSTRIAL SOURCES

Near-field sound pressure measurements may be converted into sound power levels (Lw) in order to populate propagation models. Although standards exist such as ISO 3740:2019 which present rigorous methods for the accurate determination of sound power levels, complying with such standards is not always feasible once an industry is operational. In such cases, it is common to see propagation models populated using a sound power estimate from a single field-based measurement. Alternatively, propagation models can be populated using sound power data that have been provided by equipment manufacturers or that have been presented in other standards such as BS 5228-1:2009+A1:2014. Previous papers commonly consider the isolated uncertainties associated with laboratory-based sound power assessments. This paper will explore multiple sources of error and uncertainty within near-field sound power estimates from field-based sound pressure levels and will suggest ways to minimise them.

A noise emission and vibration study of a MISTA RD-165 FHAD grader to reduce environmental harmful impact

Noise emitted by construction machinery is one of the most important harmful factors having impact on human health. The noise emission risk comprises people working on the construction site but as well as other persons around the machine. The article concerns the issues of noise level and noise emission measurements applied in heavy machinery / construction machinery which are covered by the EU directive 2005/88/EC. The methods of noise testing during design and in the certification process has been described. The basic information about testing the noise emission to the environment has been presented. The reference documents and EU standards concerning this topic has been described. The noise testing methods has been presented based on the prototyping and R&D cycle of the Mista RD-165 FHAD grader which is subjected to the European noise limits. The results of noise measurements and sound power level determination has been presented. The testing procedure where implemented during two stages of R&D cycle. The article describes the effects of the improvements in the grader focused on noise emission limitation limits.

'Attack of the Drones' Exploration of Sound Power Levels Emitted and the Impact Drone's could have upon Rural Areas, Roxwell, Essex, UK

This study considers the acoustic emission from a DJi Phantom 4 commercial drone using different rotor blades. Measurements were taken from a hovering drone with four commercial product blade configurations. Measurements were taken in accordance with (BS) EN ISO 3745: 2009 'Acoustics - Determination of sound power levels and sound energy levels of noise sources using sound pressure - Precision methods for anechoic rooms and hemi-anechoic rooms'. The aim of the project was to consider the sound characteristics emitted, specifically tonality and to determine the distance a drone could be heard from, with the different blade configurations, in a rural setting. By considering the different blade configurations within a rural setting, the role drones have within society is considered.

Road traffic noise mapping based on aerial photographs - sound power level determination of road vehicles

As the first step to obtain a city urban area noise map of road traffic noise, sound power levels of vehicles on the roads should be accurately estimated over a wide area. In Japan, ASJ RTN-Model 2018 was proposed as the representative road traffic noise prediction model, and by using the model sound power level of a vehicle can be determined if the vehicle type, traveling speed, and driving mode are known. As such data on urban road network, the Ministry of Land, Infrastructure and Transport of Japan publishes the road traffic census including road traffic volume and travel speed of major roads in Japan. The data, however, is limited to major roads and there is no data on minor roads. In this study, to estimate noise condition and situation on arbitrary road, a method for estimating the traveling speed and the traffic volume of vehicles on the road from aerial photographs was examined. Road traffic noise levels along several roads in Tokyo were analyzed by the proposed method and the validity of the calculation results were verified by comparing with short-time measurement results obtained along the target roads.

Response from Author to “Comments on Determination of Sound Power Level of Mining Equipment” by J. Parnell

In the April 2017 edition of this journal, the Author published a theoretical Technical Note in the peer-reviewed section of the journal. Commentary on that Technical Note was provided in Forum section of that same issue by Jeff Parnell of the NSW Department of Planning and Environment. The primary concerns were that simplification of the method could result in underestimation of noise impacts. This reply aims to allay some of those concerns.

Procedure for determination of sound power levels of direct-radiator loudspeakers in the low-frequency range using the sound pressure within the system enclosure

In this paper, a method of sound power level determination in the low-frequency range applied to direct-radiator loudspeakers and using the sound pressure within the system enclosure is proposed and discussed. The procedure is based on the Thiele-Small model of the loudspeaker, whereby the emitted sound power over a 2π sr solid angle is related to the total acoustic volume velocity radiated by the system, which simultaneously can be linked to the internal sound pressure in the box. Under normal conditions, this sound pressure is independent of the acoustic environment present outside the loudspeaker. To determine the internal sound pressure, the microphone could be easily inserted into the enclosure, usually through the bass-reflex opening in vented-box systems or via a small orifice in closed-box loudspeakers. The proposed method has been tested and compared with the standard methods used commonly nowadays (the reverberation room method and the anechoic room technique) on a bass-reflex loudspeaker system whose electrical analogous circuit model and sound power response are deeply known. To assess the results, the theoretical sound power response based on the electrical analogous circuit of the loudspeaker (Thiele-Small model) has been compared with all the former measurements, obtaining high agreement in the low-frequency range when the proposed method is compared with the sound power response of the theoretical model, thus validating the procedure. Even more, the measurements on the loudspeaker using the method here proposed seem to be better in the low-frequency range than that obtained by the standard methods, that is, the reverberation and the anechoic room techniques.

Sound Intensity Test Analysis of the Acoustic Enclosure for the Refrigeration Compressor

According to the international standard ISO 9614-1:1993 " Determination of sound power levels of noise sources by the sound intensity method - Part1: Measurement at discrete points, the sound intensity test was conducted on the acoustic enclosure for the refrigeration compressor with the PULSE software. The sound insulation performance of the acoustic enclosure was analyzed by comparing the compressors noise with and without the enclosure. The result shows that the noise of the compressor with the acoustic enclosure is less than 60dB (A), and the high-frequency noise can be greatly reduced, which meets the design requirements of noise control. Therefore, it is easy to conclude that the sound insulation of the acoustic enclosure reaches the design standards and the acoustic enclosure design is feasible. The paper provides a valuable reference for the further study on the designing and optimizing of the acoustic enclosure.

Nível de ruído emitido por conjuntos mecanizados em função da velocidade e da condição do solo

The noise generated by agricultural mechanization has brought side effects, and one of them is the damage to the hearing of agricultural machinery operators. According to NR-15, which establishes the tolerance limits for continuous noise, the exposure to noise levels above 115 dB (A) for individuals who are not adequately protected is not permitted, given that the maximum tolerable limit, considering an 8-hour working day, is 85 dB (A). The objective of this work was to study the influence of the travel speed and soil condition on the determination of sound power levels emitted by the tractor in several agricultural operations. The study was conducted at the Campus of Agricultural Sciences of Universidade Federal do Vale do São Francisco, Petrolina, Pernambuco, Brazil, using a Valtra tractor model 785 TDA without cabin and a noise level meter. The sound power level of the tractor was evaluated in five speeds (0.83; 1.39; 2.42; 2.97 and 3.61 m s-1) on prepared soil and soil covered with weeds, with the machinery: tractor (control), off-set disk harrow, chisel plow and rotary mower. Data were analyzed by polynomial regression when significant at least 5% probability by the F test. The most significant values were found in the tractor and plowing, observing that the need for higher engine power increased the sound power level. The other operations had noise values above the sound power established by the NR-15, considering the 8-hour working day.

NÍVEL DE POTÊNCIA SONORA NAS OPERAÇÕES AGRÍCOLAS

SUMMARY: The noise generated by agricultural mechanization brought side effects, and one of them is the damage the hearing of the operator of agricultural machinery. The NR-15 establishes the limits of tolerance for continuous noise, and exposure to the maximum allowable noise level of 115 dB (A) for individuals who are not using individual protection equipment and 85 dB (A), considering a shift work of 8 h. The objective was to study the influence of working speed and soil condition in agricultural operations in the determination of sound power levels emitted by the tractor. The study was conducted at the Center for Agricultural Sciences - UNIVASF, Petrolina / PE using a Valtra tractor model 785 TDA cabin and meter without the sound power level. We evaluate the sound power level of the tractor in five speeds (3.0, 5.0, 8.7, 10.7 and 13.0 km h -1 ) on prepared soil and ground covered with weeds, with the equipment: lightweight tandem grid, grid light off-set with discs of 55.8 cm, grade mild off-set with discs of 60.8 cm, chisel plow, mower and distributor commuting. The most significant amounts were found in the tractor and plow in operation, noting that the requirement of increased power in the engine sound power level.

Acoustic assessment of pneumatic and electric jackleg drills used in the mining industry.

Hearing loss is the most prevalent disease among miners. A study of U.S. western hard-rock mines revealed that 96% of machine operators were overexposed to noise, with jackleg drill operators having the most rapid noise dose accumulation. Traditionally, jackleg drills have been driven by pneumatic power. However, there are currently available rotary hammer drills powered by electricity. This paper presents an acoustic assessment of pneumatic and electric jackleg drills that involved noise source identification (NSID), penetration rate and operator’s cumulative noise dose measurements, and determination of sound power levels. NSID using microphone phased array technology revealed two dominant noise sources for the electric drill, one located at the drill and one located at the drill steel-rock interaction place. In contrast, NSID for the pneumatic drill showed only one dominant noise source located at the drill. Penetration rate and noise dose measurements were combined to estimate the accumulated dose and time required to drill a reference depth hole. Sound power level measurements yielded overall 115 and 125 dB(A) for the electric and pneumatic drills, respectively. The results show that the acoustic performance of the electric drill, despite its slower penetration rates, overcomes the benefits of traditional pneumatic drills.

Anechoic chamber verification for calibration of reference sound sources.

Confidence in the capability of a testing facility to perform repeatable/reproducible product testing mandates study of each test chamber utilized by the facility. The Owens Corning Acoustic Research Center (OCARC) provides product sound power level determination for many differing product types ranging from the power generation, appliance, automotive, to medical equipment industry utilizing a fully anechoic chamber with a removable horizontal reflecting plane. Recently the OARC completed a verification study identifying the performance of the chamber relative to the requirements of test standard ISO 6926: Requirements for the performance and calibration of reference sound sources used for determination of sound power levels and ANSI S12.5: Requirements for the performance and calibration of reference sound sources. These standards provide strict guidelines for the repeatability/reproducibility of test results. This paper will review the verification testing process and present results from the study.

Method of Acoustic Assessment of Machinery Based on Global Acoustic Quality Index

For the use of acoustic assessment of machinery, a global index of acoustic quality has been developed. Acoustic quality index is considered as a product of the following partial indices: sound power index, index of distance between the workstation and the machine, radiation directivity index, impulse and impact noise index and noise spectrum index. Each partial index always assumes positive value. If the value of global index does not exceed 1, the noise of the assessed machine will not exceed the admissible value of A-weighted sound pressure level at the workstation. Experimental tests were carried out in order to determine the values of global indices for a group of engine-generators, with the use of inversion method allowing for the determination of sound power level. The correctness of the determined values of indices was confirmed by the results of A-weighted sound pressure level measurements, at the hypothetically assumed workstations in simulated in situ conditions.

Considerations related to the standardization of methods for the qualification of free field test environments.

The methods for qualification of acoustic free field environments, such as anechoic and hemi‐anechoic chambers, have historically been defined in Annexes to the basic sound power standards, such as ISO 3745. However, free field test environments are used for many applications other than just sound power level determination, such as basic acoustic research, audio test, and hearing sciences. There currently are no general standards for free field qualification that addresses the unique needs of these test methods. Although the basic inverse square law qualification method is very straightforward theoretically, there are a number of practical considerations that can make this qualification method technically complex, logistically difficult, and expensive to implement. Industry standards must strike the right balance between the technical needs of the test methods and the costs associated with chamber qualification, particularly in the chamber vendor/chamber customer business environment. This paper will address some of the practical issues associated with the current inverse square law qualification method and the work of ISO Technical Committee 43, Working Group 8 that is currently in the process of developing a more general and improved document for the qualification of free field environments using this method.

Strategic Noise Mapping of the City of Ljubljana, Slovenia

Currently Ljubljana is the only agglomeration according to the definition of the directive 2002/49/EC in Slovenia. For this agglomeration, separate noise maps not only for road and rail traffic but also for industrial sources were made. As for the first phase of preparation there is no precise methodology stated for representing industrial noise sources in strategic noise maps regarding END and following the vision of other EU countries, only industrial plants classified as IPPC installations were taken into consideration of noise mapping. Short term noise measurements around industrial plants conducted according to ISO 1996 during previous three years were used as reverse engineering techniques for the determination of sound power levels of industrial plants. Elaboration of road and rail traffic noise maps required development of perfect acoustical model with 3D terrain modelling including all possible obstacles (barriers, walls, bridges, viaducts, etc.). For calibration of noise maps more then 30 measurements were performed following the standard DIN 45642. During all stages of elaborating noise maps, quality assurance procedures were performed with a view to estimate accuracy of the results. Strategic noise maps of the agglomeration performed at municipal level of Ljubljana will be used mainly for drawing up action plans and spatial planning of areas with different noise levels allowed.

Determination of sound power levels using sound pressure: The uncertainties related with the measurement surface and the number of microphones

The ISO 3740 series of standards allows the sound power levels emitted by a machine to be calculated by measuring the sound pressure levels with a limited number of microphones distributed over the surface enveloping the machine. This series of seven standards is designed for various environments and achieves three levels of accuracy. The A-weighted expanded uncertainties associated with these standards vary from 1 dB(A) to 8 dB(A). Till now, they have been obtained experimentally by using inter-laboratory measurements (reproducibility uncertainty). These uncertainties are generally overestimated. Calculation of these uncertainties would make it possible to reduce their current values. It is then necessary to determine the uncertainties related to each parameter affecting the measurement (measuring instrumentation, operating conditions, environmental correction, meteorological conditions, the finite number of microphones, the angle error, the impedance error, etc.). This paper shows the results of the calculation of the uncertainties related to the limited number of microphones, the angle error and the impedance error in the case of a free field above a reflecting plane with a hemispherical measurement surface. These uncertainties are calculated as a function of a descriptor describing the complexity of the acoustic field. The reduction of each individual uncertainty is then possible by changing several parameters of the experiment (number of microphones, distance between the measurement surface and the source, shape of the measurement surface).

Protocol for measuring dishwasher sound power levels

A leading retailer of home appliances came to the OC acoustics laboratory to evaluate the noise generated by dishwashers sold in their stores. A protocol based on a methodology used in Europe was used. It was modified to account for North American building standards. The standard provides an overall sound power level determination for the complete dishwasher cycle with and without the drying portion of the cycle. As a result customers making a purchasing decision can compare the noise performance of the various products using the same yard stick.

Determination of sound power levels of some pyrotechnic devices using sound pressure measurements

A noise measurement study was conducted at five reservoirs in New York State during the winter and summer of 2003 to determine the sound power levels generated by some specific pyrotechnic devices (bangers, screamers, and CAPAs) using sound pressure techniques. The study was performed in support of an environmental impact statement (EIS) that defined the areas around each of these reservoirs where any significant impacts would occur as a result of the pyrotechnic operations. Sound characteristic data for each pyrotechnic device was collected at short distances with a direct line of sight to the pyrotechnic sources. The sound pressure levels for each pyrotechnic device were measured in two conditions (winter and summer) to examine the accuracy of measured data. The sound power levels, including both A-weighted and C-weighted 1/1 octave band values, were calculated based upon the measured sound pressure levels. With the absence of literature and manufacturing data supports, the values of this study were believed to be the most comprehensive emission data for the EIS noise analysis.