Foreword

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The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types of ISO document should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).

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This document was prepared by Technical Committee ISO/TC 117, Fans.

This second edition cancels and replaces the first edition ( ISO 13347-4:2004 ), which has been technically revised. It also incorporates the Technical Corrigendum ISO 13347-4:2004/Cor 1:2006 .

The main changes are as follows:

inclusion of acoustic methods for installation category E fans;
symbols harmonized with those used in ISO 5801 and other ISO standards listed as normative references [2];
closer alignment with the superordinate ISO 9614 series relating to sound intensity measurement;
editorial revisions.

A list of all parts in the ISO 13347 series can be found on the ISO website.

Any feedback or questions on this document should be directed to the user’s national standards body. A complete listing of these bodies can be found at www.iso.org/members.html.

Introduction

This document establishes a method for determining the sound power level of a fan. The method is reproducible in all laboratories which are qualified according to the requirements of this document.

The method specified in this document employs standard sound measurement instrumentation. The test set-ups are generally designed to represent the physical orientation of a fan as installed, in accordance with ISO 5801 or ISO 13350 .

Since sound power levels are considered independent of the acoustic environment around the fan, a good comparison can be made between two or more fans proposed for any specific air performance condition. Moreover, these values establish an accurate base for estimating the acoustical outcome of the fan installation in terms of sound pressure levels. A successful estimate of sound pressure levels requires extensive information on the fan and the environment in which it is to be located.

It is often advantageous for the equipment user to employ acoustical consultation to ensure that all factors which affect the final sound pressure levels are considered. More detailed information on the complexity of this situation may be found in acoustic textbooks.

This document has been developed in response to the need for a reliable and accurate enveloping surface method for determining the sound power levels of fan equipment. Where possible, it has been based on existing National standards and combines state-of-the-art with practical considerations.

NOTE The bibliography contains further references for those wishing to explore this subject in greater detail (see References [1] to [7]).

1 Scope

This document specifies a method to measure sound power by using sound intensity measurements on a measurement surface which encloses the sound source. This document provides guidelines on the acoustical environment, ambient noise, measurement surface, and number of measurements. The installation categories are generally designed to represent the physical orientation of a fan installed in accordance with ISO 5801 , ISO 13350 and also defined in ISO 13349-1 .

This document is applicable to fans defined in ISO 5801 and ISO 13349-1 . This document is limited to the determination of airborne sound emission for the specified installation categories. Vibration is not measured, nor is the sensitivity of airborne sound emission to vibration effects determined.

The sizes of the fan, which can be tested in accordance with this document are limited only by the practical aspects of the test installations.

2 Normative references

3 Terms, definitions and symbols

3.1 Terms and definitions

3.2 Symbols — fan sound power levels

3.3 Other symbols

4 Instruments and methods of test

4.1 General

4.2 Reference sound source (RSS)

4.3 Calibration and field check

4.4 Performance verification

4.5 Test method

5 Equipment and installation categories

5.1 Test environment

5.2 Fan installation

5.3 Measurement surface

5.4 Reference sound source (RSS)

6 Test method

6.1 General

6.2 Sampling of sound on the measurement surface

6.3 Number of measurements

6.4 Observations

7 Calculations

7.1 Surface average level

7.2 Reference sound source adjustment, R_W

7.3 Sound power level, L_W

8 Report and results

8.1 Uncertainty of results

8.2 Presentation of results

8.3 Results

8.4 Minimum information to be reported

Bibliography