ISO 9611:1996 download

07-15-2021 comment

ISO 9611:1996 download.Acoustics Characterization of sources of structure-borne sound with respect to sound radiation from connected structures Measurement of velocity at the contact points of machinery when resiliently mounted.
ISO 9611 is one of a series of frame documents specifying various methods for the characterization of machines or equipment as sources of structure-borne sound with respect to sound radiation from connected structures.
The application of ISO 9611 to a certain family of machines needs additional requirements such as, for example, well-defined operating conditions given in a specific test code. ISO 9611 describes how, at each connection point for a resilient element, six components of the vibration can be measured and gives estimated standard deviations for their measurement uncertainty for frequencies in a given range of frequency. For a specific machine, a family of machines or for a specific application, fewer components may be sufficient to charactenze the source, thus the number of components measured could be reduced and the defined frequency range could be appropriately expanded or reduced.
01 General considerations
Airborne sound in buildings, ships and vehicles and the underwater sound radiated by ships is very often caused by vibrations of machinery or equipment. In general. such sound is emitted in at least two ways:
a) directly from the outer surface of the machine into surrounding air; measurement methods for its determination are given in the series ISO 3740 to ISO 3747 and in ISOITR 7849; and
b) from structures connected to the machine; this sound radiatEon results from structure-borne sound being emitted by the machine into the connected structures such as foundation, pipes, other coupled machines or linked auxiliary equipment.
ISO 9611 deals according to b) with machines or equipment which are sources of structure-borne sound emission into connected structures with respect to airborne or liquid-borne sound radiation of connected structures.
The measurement and evaluation of machinery vibration with respect to human response, trouble-free operation of coupled or connected mach nery, as well as structural fatigue and the lifetime of the machine itself are outside the scope of this International Standard. These fields are covered by International Standards of Technical Committee ISO/TC 108, Mechanical vibration and shock (see, for example, ISO 10816-1).
A major problem associated with the measurement of structure-borne sound emission is the choice of the quantities that characterize the ‘strength of a soirca. The complete and fully accurate characterization of a source of structure-borne sound would involve an extremely large number of measurements: thus, one has somehow to trade accuracy against the simplicity of the method. In the context of standardization, emphasis is
on simplicity; therefo4e an attempt has been made to describe the “strength by a limited number of frequency-dependent quantities.
Simplified source descriptions are possible when the two following assumptions are both satisfied:
a) the connections of the machine with the surrounding structure can be treated as ‘points”; and
bI there is a considerable mobility mismatch for all degrees of freedom of vibration at the connection points.
In such cases, the sources can be described with a limited number of force spectra if the source has relatively high mobilities, and with a limited number of velocity spectra if the source has relatively low mobilities as compared with the corresponding point mobibties of the receMng structure. An important feature is the fact that, for a certain range of receiving structures, these source descriptions are independent of the precise characteristics of the receiving structure.
For many practical purposes, the resulting source descriptions are still too complicated and a further simplification to one-, two- or three-frequency dependent quantities is necessary. The annexes give guidelines for the selection of circumstances under which further simplifications are possible.
0.2 Specific considerations
ISO 9611 is one of a series specifying various methods for the characterization of sources of structure-borne sound (i.e. for the characterization of sources of vibrations) in the frequency range of audible sound. It gives a detailed description of a first method of a series11. The results of ISO 9611 may be used for the following purposes:
a) obtaining data for preparing technical specifications;
b) comparing the structure-borne sound emission of resiliently mounted machines of the same type and size;
C) obtaining input data for planning and noise purposes (e.g. input data for the calculation of structure-borne sound Transmission through resilient mountings into the connected structure).
the method concerns the measurement of translational and angular velocity levels on the supports and other contact points of a machine which is mounted on resilient mountings (isolators). In the frequency range of the method, the selected isolators, flexible connections and foundation are such that the vibration of the contact point is not significantly affected by their presence. Consequently the results represent the free vibratory velocity levels of the contact points. The method is further restricted by the requirement that a machine support or the contact Structure of a machine to another flexible connection can be considered to vibrate as a rigid body. This implies an upper frequency limit.
The direct application of the results is limited by the above restrictions. In spite of these restrictions, there is a large variety of machines for which the method may be valuable. Examples are diesel engines, diesel gener
awrs, electric motors, compressors, fans, lathes and presses. For most of these machines, it will be possible to apply the method in the frequency range between about 20 Hz and at east 1 kHz, which is the most important frequency range for practical problems of structure-borne sound.
ISO 9611 describes measurements for all six degrees of freedom, i.e. six components of velocity (three orthogonal translations and three orthogonal rotations) at each contact. For specific machines and specific applications, some of these components can be neglected.
There is significant experience with the method for some types of machines (e.g. diesel generators for shipboard applications) which provides the basis for this International Standard.
ISO 9611 should be taken as a general document which may be used to define a standard measurement procedure for a specific class of machine. Details about the operational conditions of the machine under test, the type of mounting and foundation to be applied, the vibrational components to be taken into account, the procedure for selecting or averaging data, checks of the test arrangements and the accuracy of the method and the applicability of the results should be given.
The following International Standards were mainly consulted when preparing this International Standard: ISO 1683, ISO 2017. ISO 2041. ISO 5347-1 (and other parts), ISO 5348, ISO 7626-1. ISO 10816-1, IEC 651 and IEC 1260. To a certain extent, ISO 9611 is a further elaboration of ISO 10816-1, especially with respect to the solution of acoustical problems.

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