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Noise abatement using concurrent component-product optimisation

Deliverables

NST approach comprises the identification of internal sources of noise, the active components. This is known under the name of component source strength (CSS). The main result is the definition of the procedures of CSS identification and the test rigs for implementing it. CSS characterisation procedures have been defined and documented for different types of noise sources mechanical components involved in the project: electric motor, hermetically sealed compressor, axial fan, water pump. The fundamental characterisation concept is to replace the real source by one or more elementary sources identified via measurements. The method for characterisation of small electric motors uses: - The measurement of blocked forces in conjunction with an eddy current brake loading (structure-borne CSS) - Equivalent monopole (air-borne CSS). The characterisation of hermetic compressors is done by a 6-accelerometer method (air- and structure-borne CSS) and a 3-pressure sensor method (fluid-borne CSS). The characterisation of axial fans is done using the concept of an acoustic monopole and a rotating dipole the parameters of which are identified by measurements. The methods are described in reports. The rigs have been built and documented in reports. The documentation enables the use of the methods and reproduction of the corresponding test rigs.
Generic model of an industrial product (GSM) is the means of representing acoustically the frame (body) of the product, which plays an equally important role in noise radiation as do the primary noise sources, the mechanical components. A GSM is actually one real frame model backed by one or several sub-models the role of which is to assess the effects of design modifications on the emitted noise. A frame, and thus the GSM representing it, usually consists of several principal mechanical parts, such as supporting struts, plating etc. It was shown that the vibro-acoustic performance of the structural parts which are directly excited by noise sources and of those which ultimately radiate noise seem more important than of those corresponding to the remaining, interconnecting parts. This important finding affects the GSM design practice. GSMs for some products, such as air handling unit and washing machine are physical models, while some other types of products, such as telecommunication station or refrigerator, favour use of mathematical models implemented in numerical computation codes. Several reports have been produced describing GSM design and manufacture.
NST – a particular technology for noise control of industrial products, has been developed, validated and taken in by the project partners. Here the components – sources of noise - and the product frame (body) are first identified separately and then taken interactively at a later stage within a computer with the objective of prediction and reduction of noise of the assembled product the parts of which originate from different manufacturers. The NST technology was applied first to laboratory cases and then to real products selected by the Partners. In order to enable its use by the industry, a multi-task self-standing software named PRONS (PROduct Noise Synthesiser) was developed. The role of PRONS is prediction of product noise, selection of least noisy components and evaluation of efficient noise reduction measures. The input to PRONS is the component and frame individual characteristics. Two basic types of PRONS output results are: synthesised noise in the form of band-averaged levels and audible noise reproduction. The development of PRONS was done in three steps, with each new version adding new features and new improvements. PRONS was designed with enough flexibility to allow for a wide industrial use. It is intended for the market. Partners have demonstrated their ability to use the software.

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