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Measurement uncertainties in the determination of the sound power level and emission sound pressure level of machines.

Payne, R C; Simmons, D (1996) Measurement uncertainties in the determination of the sound power level and emission sound pressure level of machines. NPL Report. CIRA(EXT)007

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Abstract

The EC Machinery Directive 89/392/EEC requires manufacturers to declare certain basic noise information about the noise emission of their products. Underpinning the Directive is a range of ISO/CEN standards specifying agreed methods of measuring sound power level and emission sound pressure level. Most of these standards have been subject to extensive revision over the past few years, and some are completely new. The standards make it clear that measurements are subject to an uncertainty which is reflected in the reproducibility of results when the standard is applied by different organisations, by different personnel, using different equipment. This report describes a programme of measurements undertaken by four laboratories on each of four different machines to test the validity of the estimates of reproducibility given in the sound power standards ISO 3744, ISO 3746 and ISO 9614-1, and the emission sound pressure level standards ISO 11201 and ISO 11202.
The report examines: the intra-laboratory repeatability of the measurements (the ability of each laboratory to produce repeatable results); the intra-standard repeatability (the repeatability of measurements made by each laboratory to each standard over a range of different conditions within the bounds permitted by the standards); and the reproducibility of the measurements (the overall dispersion of measurements made by the four laboratories). The report also analyses differences between results obtained using hemispherical and parallelepiped measurement surfaces of different sizes in different acoustical environments, and finally inter-compares results obtained using the three sound power standards and using the two emission sound pressure levelstandards.
With the exception of ISO 3744, the experimental reproducibility standard deviations were all within the estimates published in the standards. In general, there were no statistically-significant differences between results obtained using different measurement surfaces and distances. Inter-comparison of the three sound power standards, and the two emission sound pressure level standards, showed agreement fully consistent with the experimental reproducibilities of the standards.

Item Type: Report/Guide (NPL Report)
NPL Report No.: CIRA(EXT)007
Subjects: Acoustics
Acoustics > Sound in Air
Last Modified: 02 Feb 2018 13:19
URI: http://eprintspublications.npl.co.uk/id/eprint/442

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