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1

Estimation of sound power level of machine by inverse method

Piechowicz Janusz

Vibrations in Physical Systems

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2021

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Vol. 32, nr 1

art. no. 2021113

EN

The paper presents the inverse method to estimate the sound power level of machines operated in industrial environments. Values of the partial sound power sources of machine components could be predicted based on the distribution of sound field parameters measured around the machine. Assigning partial sound power levels of machine components allows for the effective selection of efficient noise protection solutions for this machine. Measurements were carried out in an actual mechanical workshop. The multichannel measurement system for simultaneous recording of sound pressure levels and the angle of phase angle shift was used in measurements. Based on the determined the sound power of partial sources, the A-weighted sound pressure levels at the operator's workplace were determined.

2

Determinig of the sound power of the fan in in situ conditions using the virtual reference source method

Suder-Dębska Katarzyna, Czajka Ireneusz, Łojek Paweł

Vibrations in Physical Systems

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2021

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Vol. 32, nr 2

art. no. 2021206

EN

Sound power is one of the basic parameters characterizing the sound source and has a direct impact on the acoustic climate in its surroundings. Therefore, the determining of the sound power of machines is a practical problem. While there are many methods of determining the sound power, each of them has its own limitations. The authors presented the implementation of a comparative method of determining the sound power with the use of a virtual reference source. The method was used to test a high-efficiency flue gas exhaust fan installed on a laboratory stand. The sound source was placed in the geometric centre of the fan and the acoustic field distribution in the room was determined using geometrical methods. After determining the influence factors, the value of the source sound power of the source was calculated by means of the Moore-Penrose pseudo-inverse. Since the problem under study belongs to the inverse problems, the Tikhonov regularization was used, where the value of the parameter α was determined by the L-curve method.

3

Modeling of sound power transmission within duct systems

Strek Tomasz

Vibrations in Physical Systems

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2020

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Vol. 31, nr 3

art. no. 2020320

EN

External boundaries of acoustic devices can channel sound propagation, and in some cases can create buildup or attenuation of acoustic energy within a confined space. In this paper, it is proposed an efficient practical numerical method (based on FEM) of calculation of attenuation of sound power transmission through ducts. The method shows its viability by presenting the reasonably consistent anticipation of the experimental result. One can observe the mechanical behaviour of the duct’s medium for lower frequencies (high transmission loss) and wave behaviour for higher frequencies (small or zero attenuation). The authors proved that mechanical vibrations of medium reduce the possibility of acoustic energy transmission in duct systems. The radiation impedance for the duct is calculated as well.

4

The research of acoustic emission of a low-power aircraft engine

Gęca M., Pietrykowski K., Rosiński K.

Transactions on Aerospace Research

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2018

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Nr 3 (252)

19--29

EN

This paper presents the methodology and investigation of the sound power level produced by a radial piston aircraft engine operating at varied speeds. The research model aircraft engine of a maximum power of 5.5 kW with a two-bladed airscrew was placed on a test bend. Its sound power level was calculated from the sound pressure level measured at 9 measurement points distributed on a hemispherical surface in a confined space in line with PN-EN 3744. Mean sound power generated by the ASP FS400AR engine is 96 dB at idle (2,880 rpm) and 105 dB at a cruising speed (4,740 rpm). Accordingly, it can be concluded that a sound level meter registered a higher sound power level at the points in front of the model aircraft engine than at the points behind it, whereas the lowest sound power level was registered directly above the engine.

PL

W artykule przedstawiono metodologię oraz badania emisji akustycznej tłokowego lotniczego silnika w układzie gwiazda przy określonych prędkościach obrotowych silnika. Na badanym modelarskim silniku gwiazdowym o maksymalnej mocy 5,5 kW umieszczono śmigło dwułopatowe. Silnik umieszczono na stanowisku badawczym. Przeanalizowano budowę napędów lotniczych ze szczególnym uwzględnieniem modelarskich silników tłokowych, przyrządy do pomiaru poziomu dźwięku, normy i przepisy dotyczące emisji akustycznej z silników lotniczych oraz jak hałas lotniczy wpływa na zdrowie człowieka. W pracy również przedstawiono metody pomiarów akustycznych oraz elementy stanowiska badawczego. Wyznaczono poziom mocy akustycznej źródła w oparciu o pomiary poziomu ciśnienia akustycznego w 9 punktach pomiarowych na półkulistej powierzchni pomiarowej w przestrzeni zamkniętej zgodnie z normą PN-EN 3744. Przed zasadniczymi pomiarami zmierzono poziom ciśnienia akustycznego tła. Średnia moc akustyczna wytwarzana przez silnik ASP FS400AR na biegu jałowym (2880 obr/min) wynosi 96 dB a przy prędkości przelotowej (4740 obr/min) 105 dB. Na podstawie wyników stwierdzono, że miernik ustawiony w punktach znajdujących się przed silnikiem, zarejestrował wyższy poziom mocy akustycznej niż punkty znajdujące się za modelarskim silnikiem tłokowym, natomiast najmniejsza moc akustyczna wyznaczona w czasie pomiarów znajduje się bezpośrednio nad silnikiem.

5

Sound Radiation by a Cylindrical Open Cavity with a Surface Source at the Bottom

Szemela K.

Archives of Acoustics

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2018

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Vol. 43, No. 1

49--60

EN

The rigorous solution describing the sound radiation by an arbitrary surface source located at the bottom of a cylindrical open cavity embedded in a flat baffle has been obtained. The open cavities of different shapes can be found in some architectural structures as well as are components of sensors, musical instruments and vehicles. The presented formulas have been expressed in the form of Infinite sums. To use them, the infinite sums have to be truncated to the finite number of terms. Therefore, in practice, the results obtain based on the proposed solution are not exact and their accuracy is determined by the truncation error. The use of presented formulas is an alternative method for the finite element method (FEM). However, taking into account that the calculation efficiency of FEM rapidly decrease when a volume of considered region increases, the obtained in this study solution can be more useful in some practical cases. The approximated formula of a high computational efficiency has been presented for the sound pressure in the far field. The sound radiation has been analyzed for a rectangular piston as a sound source. The influence of cavity depth ratio on the radiation efficiency has been investigated. The cases for which the cavity radiation efficiency can be approximately calculated from the formula valid for a baffled sound source have been determined.

6

Metody wyznaczania poziomu mocy akustycznej źródła

Nolepa A., Kiprian K., Siemiątkowski G., Łach P.

Prace Instytutu Ceramiki i Materiałów Budowlanych

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2015

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R. 8, nr 21

43--57

PL

Podstawowym dokumentem regulującym procedury wyznaczania mocy akustycznej jest PN-EN ISO 3740: 2003 – Akustyka. Wyznaczanie poziomów mocy akustycznej źródeł hałasu. Wytyczne stosowania norm podstawowych. W normie tej przedstawiono wytyczne do stosowania serii norm międzynarodowych ISO 3740 i ISO 9614 opisujących wiele metod wyznaczania mocy akustycznej różnych typów maszyn i urządzeń. Zalecaną klasą dokładności dla celów deklarowania hałasu jest klasa dokładności technicznej, tj. klasa dokładności 2. Do badań wytypowano dwie normy PN-EN ISO 3744 oraz PN-EN ISO 3746. Norma PN-EN ISO 3744 spełnia wymagania 2 klasy dokładności, natomiast norma PN-EN ISO 3746 spełnia wymagania 3 klasy dokładności. W artykule opisano i porównano wymagania obydwu norm. Wykonano badania 9 źródeł hałasu zgodnie z normą PN-EN ISO 3744 i wyznaczono dla nich moce akustyczne. Przeprowadzono analizę spełnienia wymagań zawartych w normie PN-EN ISO 3744 wykorzystanej do badań. Wszystkie wymagania zostały spełnione, w związku z czym można było uznać wyniki badań jako wykonane z 2 klasą dokładności.

EN

The basic document regulating procedures of determination of sound power is a polish standard no. PN-EN ISO 3740 called – Acoustics. Determination of sound power levels of noise source. Guidelines for the use of basic standards – which was published in October 2003. In this standard the guidelines for the use of international standards ISO 3740 and ISO 9614 were presented, which describe different methods of determining the sound power for machinery and equipment of various types. Favoured accuracy class for the purposes of noise declaration is technical accuracy class, i.e. 2. accuracy class. Two standards PN-EN ISO 3744 and PN-EN ISO 3746 were chosen for research. PN-EN ISO 3744 meets requirements 2. accuracy class and PN-EN ISO 3746 meets requirements 3. accuracy class. In this paper the requirements of two standards were described and compared. The research of 9 noise sources according to PN-EN ISO 3744 standard were performed and the sound powers were determined for these sources. The analysis of the requirements used in this standard was performed. All the requirements were met therefore the research results were accepted as performed according to the accuracy class 2.

7

Sound Radiation from a Surface Source Located at the Bottom of the Wedge Region

Szemela K.

Archives of Acoustics

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2015

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Vol. 40, No. 2

223--234

EN

Applying rigorous analytical methods, formulas describing the sound radiation have been obtained for the wedge region bounded by two transverse baffles with a common edge and bottom. It has been assumed that the surface sound source is located at the bottom. The presented formulas can be used to calculate the sound pressure and power inside the wedge region. They are valid for any value of the wedge angle and represent a generalization of the formulas describing the sound radiation inside the two and three-wall corner region. Moreover, the presented formulas can be easily adapted for any case when more than one sound source is located at the bottom. To demonstrate their practical application, the distribution of the sound pressure modulus and the sound power have been analyzed in the case of a rectangular piston located at the wedge’s bottom. The influence of the transverse baffle on the sound power has been investigated. Based on the obtained formulas, the behaviour of acoustic fields inside a wedge can be predicted.

8

A Numerical Approach to Calculate the Radiation Efficiency of Baffled Planar Structures Using the Far Field

González-Montenegro M. A., Jordan R., Lenzi A., Arenas J. P.

Archives of Acoustics

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2014

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Vol. 39, No. 2

249--260

EN

A numerical method is developed for estimating the acoustic power of any baffled planar structure, which is vibrating with arbitrary surface velocity profile. It is well known that this parameter may be calculated with good accuracy using near field data, in terms of an impedance matrix, which is generated by the discretization of the vibrating surface into a number of elementary radiators. Thus, the sound pressure field on the structure surface can be determined by a combination of the matrix and the volume velocity vector. Then, the sound power can be estimated through integration of the acoustic intensity over a closed surface. On the other hand, few works exist in which the calculation is done in the far field from near field data by the use of radiation matrices, possibly because the numerical integration becomes complicated and expensive due to large variations of directivity of the source. In this work a different approach is used, based in the so-called Propagating Matrix, which is useful for calculating the sound pressure of an arbitrary number of points into free space, and it can be employed to estimate the sound power by integrating over a finite number of pressure points over a hemispherical surface surrounding the vibrating structure. Through numerical analysis, the advantages/disadvantages of the current method are investigated, when compared with numerical methods based on near field data. A flexible rectangular baffled panel is considered, where the normal velocity profile is previously calculated using a commercial finite element software. However, the method can easily be extended to any arbitrary shape. Good results are obtained in the low frequency range showing high computational performance of the method. Moreover, strategies are proposed to improve the performance of the method in terms of both computational cost and speed.

9

Badania hałasu infradźwiękowego generowanego przez turbiny wiatrowe przy użyciu normy pn-en 61400-11

Malec T.

Zeszyty Naukowe. Elektryka / Politechnika Opolska

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2012

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z. 67

59-61

PL

Opis sposobu rozszerzenia normy PN-EN 61400-11 do wyznaczania poziomu mocy akustycznej turbin wiatrowych w zakresie infradźwiękowym.

EN

Describes how to extend the standard PN-EN 61400-11 to determine the sound power level wind turbines in the infrasound range.

10

Modelowanie rozkładu wskaźników hałasu ulotu w otoczeniu linii wysokiego napięcia

Wszołek T.

Przegląd Elektrotechniczny

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2010

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R. 86, nr 11b

111-114

PL

W pracy pokazano model do obliczania poziomu mocy akustycznej jednostkowej długości przewodów fazowych w funkcji intensywności opadów, stanu technicznego oraz wysokości zawieszenia przewodów dla dowolnego układu geometrycznego linii WN. Przykładowe obliczenia rozkładu wskaźników długookresowych hałasu ulotu przeprowadzono w przekrojach poprzecznych oraz w postaci mapowej dla zróżnicowanych uwarunkowaniach terenowych.

EN

The paper shows a model to calculate the sound power level of unit length phase conductors as a function of rainfall intensity, the technical condition and the height of the suspended conductors for any geometric arrangement of power line. Sample calculations of the distribution of the long-term noise indicators were performed in cross sections and the form of maps in diverse terrain considerations.

11

Determination of the sound power of a machine inside an industrial room by the inversion method

Piechowicz J.

Archives of Acoustics

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2009

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Vol. 34, No. 2

169-176

EN

Utilisation of the substitute sources system consisting of monopole sound sources is one of the methods of sound sources modelling in the industry. The knowledge of the actual acoustic pressure distribution around industrial sound sources is necessary for determination of the parameters of such models. In order to satisfy requirements, the distribution of acoustic pressure amplitudes as well as the distribution of phase shift angles between acoustic signals are to be determined. The presented investigations constitute a part of the research program related to the application of inversion methods in the assessment of acoustic parameters of machines operating under industrial conditions, as well as to the comparative analysis of the hereby obtained results with the results obtainable by other methods of testing.

12

The influence of a vibrating rectangular piston on the acoustic power radiated by a rectangular plate

Zawieska W. M., Rdzanek W. P.

Archives of Acoustics

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2007

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Vol. 32, No. 2

405-415

EN

The equation of motion of a flat simply supported rectangular plate has been solved. The plate has been excited by a surface force. The influence of the acoustic pressure radiated by the plate on its vibrations has been included. The corresponding sound pressure distributions have been presented as their backward Fourier transforms. The acoustic active and reactive sound power has been computed including the influence of the sound pressure radiated by the piston. The acoustic mutual sound power of both sources has also been presented.

13

Reduction of the sound power radiated by a two pistons system located near the three-wall corner

Rdzanek W. P., Szmela K.

Archives of Acoustics

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2007

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Vol. 32, No. 2

339-350

EN

The main aim of this study is to calculate magnitudes describing the sound radiation by a system containing two vibrating circular pistons located in tree-wall corner. It is assumed that there is no influence of the surrounding medium on the sources vibrations and the vibration velocities of the pistons are time-harmonic. Making use of the known form of the Green function valid for tree-wall corner area the formulae presenting the acoustic pressure radiated by considered sources has been obtained. In order to characterize the sound radiation of the examined system of sources the self and the mutual powers in the integral form have been also expressed. Employing the well known integral expressions the obtained formula for the self power can be presented in the form of the fast convergent sum. The investigations presented herein can be very useful for a projection systems containing some vibrating pistons. On the basis of the presented in this paper formulae the acoustic properties of the vibrating pistons embedded in tree-wall corner can be predicted. It can be very advantageous to design vibrating systems and helpful to reduce harmful noise.

14

Acoustic modelling of machines using the inversion method for the purposes of the acoustic assessment of machines

Pleban D.

Archives of Acoustics

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2007

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Vol. 32, No. 2

321-327

EN

Issues related to the development of acoustic models of machines are important factors both in the design of low-noise machines and in the prediction of machines noise. The acoustic modelling of machines may be carried out using a set of omni-directional substitute sound sources, located in points related to the functional elements of machines. The optimal parameters of these sources may be determined using an inversion method. To calculate these parameters by using the inversion method one must know the real distribution of sound pressure around the machine. This requires the determination, on the surface of hemisphere, of both the distribution of the amplitude of sound pressures, as well as the distribution of phase shift angles between acoustic signals. Computer simulations yield optimal parameters (sound power) for the individual omni-directional sound sources. Using the calculated parameters of the substitute sources it is possible to determine the radiation characteristics and to carry the acoustic assessment of the machine.

15

The influence of constructional parameters on stiffened plates sound radiation

Iwaniec M.

Archives of Acoustics

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2005

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Vol. 30, No. 4

483-494

EN

This work concerns the method of the plate parameter selection and the choice of the stiffening set, assuming the minimization or maximization of the energy stored or radiated by a stiffened plate as a criterion. The energy balance equations based on the SEA method were used in order to quickly evaluate the energy flow as a function of chosen constructional parameters. Calculations of mechano-acoustic energy flow were performed in AutoSEA and Matlab environment.