Place Of Installation Research Articles

Developments in Non-Fire Sensitivity Testing of Optical Smoke Detectors - Proposal for a New Test Method

The purpose of an automatic fire detection system is the fast and reliable detection of arising fires in order to keep damage as low as possible. The European Standard EN54 defines a series of tests to prove and certify the functionality of smoke detectors, i.e. to prove that the detector is able to detect a fire in a prescribed period of time. Unfortunately the complex problem of avoiding false alarms is not completely addressed. In contrast to the well standardised methods for the evaluation of the detection capability of a smoke detector, there is a lack of a reproducible and representative test method concerning the false alarm susceptibility with regard to nuisance aerosols. The consequences of false alarms should not be underestimated, as they may cause several costs to the operator, especially in airborne applications. Several approaches are possible to reduce the false alarm susceptibility of optical smoke detectors, e.g. different wavelengths and scattering angles. Unfortunately the developer has no test methods to quantify improvements due to new developments. This paper presents a new approach for the test of smoke detectors regarding their susceptibility to false alarms due to nuisance aerosols, like steam and dust. Fog and spray tests in the developed set-up are planned. The presented test apparatus is a helpful tool for developers as well as for test houses during the developing and certification process. System designer will have a decision criterion to find an adequate detector for a specific place of installation. The objective of the project was the development of a standardised test method for sensitivity tests of fire detectors to hazardous substances. The presented test apparatus has been developed in a cooperation of Airbus and the University of Duisburg-Essen and can contribute to a test standard. The design is similar to the EN54 test duct, however due to its small volume of only around 32 l, the duct is much smaller, easier to clean, portable and cheaper. The duct allows a qualitative statement on the sensitivity of the tested detector regarding nuisance aerosols with reproducible results. Also a slow pollution with dust of the measuring chamber can be emulated. The achieved results of this study are a promising first step in the development of a new test standard.

Developments in Non-Fire Sensitivity Testing of Optical Smoke Detectors - Proposal for a New Test Method

The purpose of an automatic fire detection system is the fast and reliable detection of arising fires in order to keep damages as low as possible. The European Standard EN54 defines a series of tests to prove and certify the functionality of smoke detectors, i.e. to prove that the detector is able to detect a fire in a prescribed period of time. Unfortunately the complex problem of avoiding false alarms is not completely addressed. In contrast to the well standardised methods for the evaluation of the detection capability of a smoke detector, there is a lack of a reproducible and representative test method concerning the false alarm susceptibility with regard to nuisance aerosols. The consequences of false alarms should not be underestimated, as they may cause several costs to the operator, especially in airborne applications. Several approaches are possible to reduce the false alarm susceptibility of smoke detectors, e.g. different wave lengths and scattering angles. Unfortunately the developer has no test methods to quantify improvements due to new developments. This paper presents a new approach for the test of smoke detectors regarding their susceptibility to false alarms due to nuisance aerosols, like steam and dust. Fog and spray tests in the developed set-up are planned. The presented test apparatus is a helpful tool for developers as well as for test houses during the developing and certification process. System designer will have a decision criterion to find an adequate detector for a specific place of installation. Target of the project was the development of a standardised test method for sensitivity tests of fire detectors to hazardous substances. The presented test apparatus has been developed in a cooperation of Airbus and the University of Duisburg-Essen and can contribute to a test standard. The design is similar to the EN54 test duct, however due to its small volume of only around 32 l the duct is much smaller, easier to clean, portable and cheaper. For an accurate and reproducible aerosol feeding the duct has been combined with a commercialised particle generator. The particle generator Palas RBG 1000 disperses a pre-defined amount of standardised dusts. With the developed duct, detector tests under different flow directions and velocities can be performed in the same way as with the EN54 test duct. An optical reference measurement of the aerosol concentration is performed by a light extinction path in the infrared range. The duct allows a qualitative statement on the sensitivity of the tested detector regarding nuisance aerosols with reproducible results. Also a slow pollution with dust of the measuring chamber can be emulated. The achieved results of this study are a promising first step in the development of a new test standard.

TRANSLATIONS OF SERVICE LEVEL AGREEMENT IN SYSTEMS BASED ON SERVICE-ORIENTED ARCHITECTURES

The gain of the article is to introduce and to discuss a formal specification of a computer system's service level agreement (SLA) and its translation into the structure of complex services (composed of atomic services) delivering required functionalities and nonfunctionalities in a distributed environment. It is assumed that the SLA is composed of two parts specifying quantitative and qualitative requirements. The former requirements define the structure of the adequate complex services in form of a directed graph, where potential parallelism of atomic services performance may be taken into account. The latter—qualitative requirements—are applied to select the optimal complex service realization scenario; it is based on assumption that various atomic services distinguished in the complex services structures are available at the considered distributed environment in different versions and locations. Different versions of atomic services are atomic services delivering the required functionalities and satisfy nonfunctionalities at various levels. Different locations (installation place) of available atomic services means that the cost of atomic services delivery (communication and calculation) depends on parts of the distributed systems where the services are performed. The proposed model of SLA translation into complex services structures and variants may be applied—among others—to calculate upper and lower complex services' delivery times and to estimate the validity of possible parallelism in complex services.

입자추적기법을 이용한 바다숲 조성지의 확장에 관한 수치예측

바다숲 조성용 시설물의 효율적인 배치를 위하여 수치실험을 통하여 바다숲 조성 예정지의 조석류에 의한 해수흐름을 분석하였으며, 분석된 해수흐름을 바탕으로 하여 해조포자의 거동을 파악하기 위하여 입자추적실험을 수행하였다. 수치실험에 사용된 수치모형은 EFDC(Environmental Fluids Dynamics Code)를 사용하였으며, 연직방향으로 총 5개 층으로 나누어 실험을 수행하였다. 실험결과, 바다숲 조성대상해역의 해수흐름패턴은 대상해역 바깥쪽의 주류에 크게 영향을 받고 있음을 알 수 있었고, 잔차류를 분석한 결과 크게 두 개의 순환 고리가 형성되어 있음을 확인하였다. 해수흐름의 패턴을 고려하여 3곳의 바다숲 시설물의 설치장소를 선정하고 저층에 입자를 투입하여 15일간 추적을 실시한 결과, 1번과 3번 정점은 해안선에 연하여 띠형태로 시설하며, 2번 정점은 연안에서 약 300 ~ 500m정도 떨어진 곳에 타원의 형태로 시설하는 것이 보다 효율적일 것으로 판단되었다.

Measurement of Micro Vibration of Car by Piezoelectric Ceramics -Detection of Bio-Informations in the Car and Application for Security-

Recently, there are various accidents and crimes related to the car. In some cases, the accidents and the crimes can be prevented if it is possible to detect a human who is in the car. For example, we can prevent a baby who is left in a car under the hot weather from dehydration or death occurred by heat inside disease. In another case, it is estimated that the United States currently has as many as 12 million illegal immigrants. In order to prevent further influx of illegal immigrants, the police are physically searching incoming vehicles at national boundaries aiming at finding those who are hiding inside. However, the physical inspections require much manpower cost and time. An inspection method to see inside the vehicles through X-ray images has also been used for this end. But the cost and the installation places are the problems of the large-scale X-ray system. Proposed in this paper is a piezoelectric ceramic system to handily measure the micro vibrations of motor vehicles. And applying the algorithm of Support Vector Machine (SVM), the existence of human body inside vehicles can be detected. The experiment was carried out using four types of vehicles: a mini car; an auto mobile; a van; and a truck weighing 1.5 tons. As the results, the correct determination ratio was 91.2% for the experiment with the piezoelectric ceramic under the front wheels and 97.0% under the rear wheels, when the vehicle used for the examination had also been used together with other three types of vehicles to obtain SVM training data. When the vehicle used for the examination had not been used together with the other three to obtain SVM training data, on the other hand, the correct determination ratio was 93.7% for the experiment with the piezoelectric ceramic under the front wheels and 95.7% under the rear wheels.

Sensor Placement to Improve the Positioning Performance Based on Angle of Arrival (AOA)

In this paper, a method for sensor placement to improve the placement quality based on angle of arrival of signal in a specific area is proposed. The installation place of sensors may be constrained with specified boundaries. In this me-thod, the criterion of maximum quality of placement is the Cramer-Rao bound. The generalized pattern search as an effective method is used to maximize error bound of the placement problem by angle of arrival. Better results are ob-tained in comparison with results of genetic algorithm. The derived results are compared from two aspects of run time and result quality.

Reducing the rail component of rolling noise by vibration absorber: theoretical prediction

A compound track—absorber model is employed to study the performance of a rail vibration absorber in reducing the rail component of rolling noise. The rail vibration and radiation due to a roughness excitation are calculated with the use of the absorber. Different types of rail absorber and installation locations are considered in calculations to investigate their influence on the absorber's performance. The theoretical predictions show that the rail-radiated noise can be reduced by about 6—8 dB(A) using the rail absorber for the situation modelled here. The most appropriate installation place for a discrete absorber is at mid-span between sleepers because the vibration response there is large. As the rail vibration amplitude is small at sleepers, they are not the appropriate installation place for a discrete absorber to reduce rail radiation via energy dissipation. It should be noticed that the performance of the rail absorber is predicted under idealized conditions, and the noise reduction that can be achieved using the absorber is dependent on some practical factors, which are not further studied in this work.

시험 선로 결빙 방지를 위한 전기 가열식 융설 및 융빙 시스템의 최적 조건에 관한 연구

The snow melting system by electric heating wires which is adopted in this research is a part of road facilities to keep surface temperature of the road higher than freezing point of water for melting the snow accumulated on it. The electric heating wires are buried under paved road at a certain depth and operated automatically and manually. Design theory, amount of heating, and installation standard vary according to economic situation, weather condition, installation place and each country applying the system. A main purpose of this study is figuring out the appropriate range of required heat capacity and installation depth and pitch for solving snowdrifts and freezing problems with minimum electric power consumption. This study was performed under the ambient air temperature( 2 C, 5 C), the pitches of the electric heating wires(200 mm, 300 mm), heating value(250 W/m 2

RESEARCH AND ASSESSMENT OF WIND TURBINE'S NOISE IN VYDMANTAI/VYDMANTŲ VĖJO JĖGAINĖS KELIAMO TRIUKŠMO TYRIMAI IR ĮVERTINIMAS/ИССЛЕДОВАНИЕ И ОЦЕНКА ШУМА ВИДМАНТАЙСКОЙ ВЕТРЯНОЙ ЭНЕРГОУСТАНОВКИ

The decreasing reserve and growing costs of coal, oil and gas has persistently led us to use renewable energy resources. Using them environmental harm, air pollution and greenhouse effect can significantly be decreased. According to the European Union Parliament's and Council Directive 2001/77/EC approved in July 27, 2001, the member countries (Lithuania has been a member country from May 1, 2004) must seek to use not less than 12 per cent of renewable energy sources in total energy balance and 22,1 percent in the country's energy balance (including large hydroelectric power station). The numbers are significant. Thus, using wind energy can be one of the ways to fulfil the requirements. Lithuanian seaside, where the strongest winds are blowing, has been the most favourable place for the wind turbine's installation. However, usage and development of wind energy has been facing resistance from the society. One of the biggest arguments against the wind turbine is the noise which can cause inconveniences for the permanent residents and holidaymakers of the health‐resort zone. Therefore, environmental impact of the wind turbine requires exhaustive investigations. The research was carried out in the vicinity around the only one presently active industrial wind turbine in Vydmantai (region of Klaipeda, Lithuania). During the investigation it was established that the highest noise level was registered opposite the airscrew. The smallest noise level was measured in both sides from the tower in windscrew plane. It has been measured that noise level is noticeably higher in Vydmantai wind turbine's zone than in the background, which does exceed 250–300 m (5–6 windscrew diameters). Santrauka Mažejančios akmens anglies, naftos ir duju atsargos elektros gamyboje verčia naudoti kitus energijos šaltinius, tokius kaip atsinaujinantieji energijos šaltiniai, kurie gali sumažinti aplinkos žalojima, atmosferos teršima, šiltnamio efekta. Remiantis Europos Sajungos Parlamento ir Tarybos 2001 07 27 direktyva 2001/77/EB šalys nares (nuo 2004 05 01 ir Lietuva) turi siekti, kad 2010 m. atsinaujinančiuju energijos ištekliu dalis bendrame energijos balanse sudarytu ne mažiau kaip 12 %, o šalies elektros balanse 22,1 % (su didelemis hidroelektrinemis). Tai dideli skaičiai. Šis padidejimas galimas visu pirma pasitelkus vejo energetika. Šiuo metu pastebeta, kad vejo energetika susilaukia visuomenes pasipriešinimo. Vienas iš pagrindiniu motyvu ‐ šiu jegainiu keliamas triukšmas. Atsižvelgiant i tai, kad vejo jegainiu statybai Lietuvos pajūris yra palankiausia vieta, kur yra daug smulkiu gyvenviečiu ir poilsiaviečiu zonu, šiam vejo jegainiu poveikiui ištirti reikejo papildomu išsamiu tyrimu. Šie tyrimai buvo atlikti Vydmantuose (Klaipedos rajonas) prie veikiančios pramonines vejo jegaines. Tyrimais nustatyta, kad didžiausias triukšmo lygis buvo registruotas priešais vejarati. Mažiausias triukšmo lygis buvo išmatuotas i abi puses nuo bokšto vejaračio plokštumoje. Vydmantu vejo jegaines zona, kurioje triukšmu lygis yra didesnis nei foninis, neviršija 250–300 m (5–6 vejaračio skersmenys). Резюме Уменьшающиеся запасы каменного угля, нефти и газа способствуют применению альтернативных источников энергии для её получения, например, возобновляемых источников энергии, которые могут уменьшить наносимый окружающей среде вред, а также снизить уровень загрязнения атмосферы и тепличный эффект. Руководствуясь директивой Европейского Союза 2001/77/ЕС, страны, входящие в его состав (с 01-05-2004 и Литва), должны стремиться к тому, чтобы к 2010 г. часть электроэнергии, получаемой из возобновляемых источников энергии, составляла не менее 12 % в общем энергетическом балансе и 22,1 % (включая крупные гидроэлектростанции) в энергетическом балансе страны. Это большие цифры. Их достижение возможно прежде всего благодаря использованию энергии ветра. Однако в настоящее время ветроэнергетика вызвала недовольство общественности. Одним из основных мотивов недовольства является шум, распространяемый ветряными электростанциями. В Литве наиболее приемлемым местом для строительства ветрогенераторов является приморье, где находится много мелких населённых пунктов, а также зон туризма и отдыха, поэтому фактор общественного недовольства требует серьёзных всесторонних исследований. С этой целью исследовался шум, распространяемый ветряной электроустановкой, находящейся в городе Видмантай (Кретингский р-он). Результаты исследования показали, что наибольший уровень шума наблюдался перед ветровиком, а наименьший – по обе стороны от башни установки в плоскости ветровика. Зона, в которой уровень шума выше фонового, не превышает 250–300 м (5–6 диаметров ветровика).

Installation Places of Criticality Accident Detectors in the Plutonium Conversion Development Facility

At the Plutonium Conversion Development Facility (PCDF) in the Nuclear Fuel Cycle Engineering Laboratories, the co-conversion technologies to purify the mixed plutonium and uranium nitrate solution discharged from a reprocessing plant have been developed. The probability of a criticality accident in PCDF is extremely low. However, the criticality accident alarm system (CAAS) has been in place since 1982 to reduce the radiation dose to workers in case of such a rare criticality accident. The CAAS contains criticality accident detector units (CADs), one unit consisting of three plastic scintillation detectors, and using the 2 out of 3 voting system for the purpose of high reliability. Currently, eight CADs are installed in PCDF evaluating the dose using a simple equation allowing for a safety margin. The purpose of this study is to show the determination procedures for the adequate relocation of the CADs which adequately ensures safety in PCDF.

일반용 전기설비의 원격 전기안전 감시를 위한 수용가 설치 장치 모델

대부분의 전기화재와 부재로 인한 미점검 문제가 발생하고 있는 일반용 전기설비의 효율적 안전관리를 위한 원격감시시스템의 도입을 위해서는 비용과 설치를 고려한 수용가 장치 모델의 개발이 필요하다. 본 논문에서는 일반용 전기설비의 원격 전기안전 감시를 위한 수용가 장치 모델들을 제시하였고 일반용 전기설비 설치 장소에 따른 합리적 모델을 찾기 위해 비용, 설치 및 통신 방법을 비교하였다. 그 결과 일반용 전기선비의 대부분을 차지하고 있는 주택 전기설비의 원격 전기안전 감시를 위한 합리적 모델은 저압원격겁침 계량기에 안전감시 기능을 부여하는 것으로 나타났다.

Spectroscopic characterization of a microplasma used as ionization source for ion mobility spectrometry

We report a miniaturized excitation source for soft ionization of molecules based on a dielectric barrier discharge. An atmospheric plasma is established at the end of a 500 μm diameter capillary using He as buffer gas. The plasma jet which comes out of the capillary is dependent on the gas flow rate. The mechanism of the production of N 2 + outside the capillary, which is relevant for the protonation of molecules and sustains the production of primary ions, is investigated by spatially resolved spectroscopic measurements throughout the plasma. Possible application of such miniaturized plasmas is the ionization of gaseous compounds under atmospheric pressure as an alternative to traditional APCI (atmospheric pressure chemical ionization). The miniaturized plasma was applied as ionization source for ion mobility spectrometry where the common sources are radioactive, thus limiting the place of installation. First measurements of gaseous compounds with such a plasma ion mobility spectrometer with promising results showed detection limits comparable or even better than those obtained using common radioactive ionization sources.

Sistematização do dimensionamento técnico e econômico de sistemas fotovoltaicos isolados por meio de programa computacional

Uma das principais questões referentes à energia solar é como compará-la, técnica e economicamente, com outras fontes de energia, tanto alternativas quanto com as convencionais (como a rede elétrica). O propósito deste trabalho foi desenvolver um programa computacional que reúne os principais dados técnicos e econômicos, para identificar, por meio de métodos de análise microeconômica, a viabilidade comercial no dimensionamento de sistemas fotovoltaicos, além de considerar os benefícios provenientes da própria geração energética. Na análise microeconômica da energia solar, foram identificados os custos da energia proveniente da rede convencional durante o período de vida útil dos componentes do sistema gerador de eletricidade fotovoltaica, pelo estudo dos custos de investimentos iniciais e manutenção do sistema. Para comparação com as fontes convencionais - rede elétrica e grupo diesel - foram usados três cenários de custos de painéis fotovoltaicos e dois para o fator de disponibilidade do grupo diesel. Pelos resultados, verifica-se que, quanto mais baixo o custo dos painéis e mais distante o local situar-se da rede elétrica, o sistema fotovoltaico torna-se a opção mais vantajosa.

RΟCKFALL S DURING THE EARTHQUAKE OF 14/8/03 AND PROBABLE SOLUTIONS AT THE UPPER LEVEL OF DRIMONA S VILLAGE SLOPE, MUNICIPALITY OF SFAKIOTON LEUKADA ISLAND

Big rocky blocks of indicative dimensions of 2.5*2.5x2.5 m, were activated and fell down-slope during the earthquake (Ms=6.4) of 14/8/03 from the upper part of the hill slope behind Drimon village (Municipality of Sfakiotes in Leukada island). The area is geologically composed of thick bedded white neritic limestones, of Pantokratoras unit (Upper Triassic age). The slope angle is roughly 50° to the NW, at the place of rockfall activation. The limestone is cut in blocks of edge 2-3 m long, due to the geometry of the tectonic discontinuities and the orientation of bedding. In this paper, the mechanism of rockfalls was studied regarding to their horizontal and vertical jumps as well as their kinetic energy. Furthermore, the type, the geometry, the place of installation and the necessary absorbing capacity of barriers were studied for restraining future rockfalls in the area. According to our study, the blocks are necessary to be tied, in place, at the upper part of the slope, using bolting, wire cable and wire netting techniques. Nevertheless, two elastic metallic barriers, approximately 100 m long and 5 m high, able to absorb kinetic energy of 3000 kJ, were decided to be installed on the slope, for the case that blocks, of mean dimensions 2.5x2.5x2.5 m, fall down. These barriers will be placed at horizontal distances of 38.22 m and 94.08 m, from the rockfalls starting point.

Environmental impact of combustion

Large amounts of fuels, burned in various types of furnaces are one of the main sources of pollution in the environment. Flue gases pollute the atmosphere and the associated ashes pollute soil and water. To compare the influence of various fuels burned in different installations on the environment, one universal index would be helpful. Such a coefficient, which represents the harmfulness of combustion processes of a particular fuel in a particular installation, is defined in this paper. This coefficient takes into account the composition of the fuel, the thermal efficiency of the installation, the type and process efficiency of creation of harmful compounds in the combustion chamber, efficiency of cleaning devices, ability of emitter to propagate pollutants into the atmosphere, as well as the relative toxicity of various components. Finally methods of calculation of propagation of pollutants in the atmosphere are introduced. All these factors are essential for a reliable assessment and comparison of fuel and installations. An individual coefficient of harmfulness could be calculated for each compound present in the flue gases as well as a total coefficient for all compounds. Each compound created in the combustion processes is the source of many types of environmental impact. It could have significant influences on human health, plants and animals as well as for example on the corrosion process taking place in many different installations. We have to take into consideration that the result of a combustion process could appear in many different places, sometimes distant from the place of the process itself. All these results should be analyzed and introduced into the universal coefficient of “harmfulness” of specific compound. Economic parameters and methods are important and therefore are also introduced into the assessment method presented in the paper. In this way we are able to compare the values of extremely different phenomena such as a human health and corrosion.

Crimped metal ribbon flame arrestors for the protection of gas measurement systems

Abstract This paper summarises the results of extensive research to determine the limit of safety against flame transmission for flame arrestors of relatively small size fitted with arrestor elements made of crimped metal ribbon. Depending on the reactivity of the fuel gas/air mixture and the tube geometry the running up to detonation and hence the stressing of a flame arrestor by a detonation is possible in longer tubes with relatively small diameters. Only with reactive gas phases of explosion group I this stressing case for a flame arrestor can be excluded. With detonative gas phases the stressing of the flame arrestor decisively depends on the place of installation with respect to the point of transition from deflagration to detonation in the system considered. Five different stressing cases with a probably very different limiting pressure of safety against flame transmission must be distinguished. The results of the investigations will help to evaluate the results from testing of flame arrestors carried out according to the requirements in national and international standards or regulations.

Characterization of Fibers in an Existing Network for High Speed System (10Gb/s or Greater) Compatibility

With OC-192 communications systems being commercially available and higher bit rate systems in development, prudent telecommunications network administrators are testing their installed fibers to determine if they can be successfully used at 10 Gb/s and higher. Together with New Brunswick Telephone (NBTel), the Fiber Optics Group at UNB have tested various installed fibers and cables in the NBTel network for their losses at wavelengths of 1244, 1310, 1550, and 1625 nm, as well as for strain and polarization mode dispersion (PMD). Weather conditions, age, place of installation, and cable types have also been considered. Aging does not seem to affect the performance of the fibers. Although most fibers are high-speed system compatible when looking at attenuation measurements, about 40% of the fibers tested would not meet the 10 Gb/s OC-192 system manufacturer's design guidelines concerning PMD.

Characterization of Fibers in an Existing Network for High Speed System (10Gb/s or Greater) Compatibility

With OC-192 communications systems being commercially available and higher bit rate systems in development, prudent telecommunications network administrators are testing their installed fibers to determine if they can be successfully used at 10 Gb/s and higher. Together with New Brunswick Telephone (NBTel), the Fiber Optics Group at UNB have tested various installed fibers and cables in the NBTel network for their losses at wavelengths of 1244, 1310, 1550, and 1625 nm, as well as for strain and polarization mode dispersion (PMD). Weather conditions, age, place of installation, and cable types have also been considered. Aging does not seem to affect the performance of the fibers. Although most fibers are high-speed system compatible when looking at attenuation measurements, about 40% of the fibers tested would not meet the 10 Gb/s OC-192 system manufacturer's design guidelines concerning PMD.

Control of Angular Motion of the Robotic Space Module Transporting a Flexible Load

Consideration was given to designing the optimal control of a free-flying robotic space module equipped with relay actuators which carries a bulky flexible load. The procedure of designing a spatial modal-physical model of the robotic space module with a flexible load was described. For this construction, numerical analysis of the dynamic “portrait” which accompanies the model enables one to establish the profile of its elastic oscillations which has the form of a multiextremal function in the space of possible values of the coordinate of the point where the load is gripped by the manipulator. The global extremum (minimum) of this dependence, which was accepted as the goal function, was used as a criterion for designing the algorithm optimizing the gripper position on the load axis upon stabilizing the angular motion of the module. The calculated extremum is used in the loop of adaptive adjustment of the gripper parameter, which prevents resonance swinging of the flexible load transported to the place of installation.

Bestimmung der Schalleistung von Zentrifugen über Schallintensitätsmessungen

AbstractThe sound pressure level measured at a distance of one meter is frequently used to assess the sound emission of a machine. The sound pressure level depends on the measuring distance, the directivity pattern, if any, of the machine and on the sound‐absorbing properties of the place of installation. Because it is a local field parameter it is not very suitable for ascertaining the sound emission of a machine. In contrast to, the sound power level is far more suitable because the influence mentioned earlier can be corrected and the value is reproducible for any random test condition. Generally, it is calculated from the results of sound pressure level measurements by application of the standardised enveloping surface method. Concerning sound intensity measurements a special probe allows ascertainment of the sound intensities directly on the enveloping surface. Despite an initially elaborate measuring technology, this method is in fact often faster and more exact than the enveloping surface method because it does not require subsequent correction to determine the sound power level. The benefits and drawbacks of sound pressure and sound intensity measurements are compared with each other on the basis of measurements on centrifuges directly related to practical operation.