Foreword

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This document was prepared by Technical Committee ISO/TC 70, Internal Combustion Engines.

This second edition cancels and replaces the first edition ( ISO 15619:2013 ), which has been technically revised.

The main changes are as follows:

added sources for terms and definitions cited in clause 3.
deleted 4.2.1.2 of the original document;
described the use of the instrument in the 7.1 as a separate subclause, 5.3;
removed duplicate descriptions mentioned in ISO 3046-1 and revised the text appropriately in 6.4 and 7.3.2;
moved 1.1 in the original document to 7.2;
revised descriptions in A.3.3;
bibliography supplement.

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 specifies methods for measuring the sound power level of exhaust noise and the insertion loss of exhaust silencers installed on reciprocating internal combustion engines and a method for measuring the power loss ratio of reciprocating internal combustion engines.

Sound power level of exhaust noise, insertion loss, and transmission loss are parameters to characterize the acoustic performance of exhaust silencers. Sound power levels of exhaust noise and insertion loss are important parameters to characterize the acoustic matching performance of exhaust silencers and reciprocating internal combustion engines. Transmission loss is the difference in sound power level of exhaust noise between the noise before and after transmitting through the exhaust silencer, which is the parameter to characterize the acoustic performance of the exhaust silencer itself and not relevant to the reciprocating internal combustion engine. Power loss ratio and pressure loss are parameters to characterize the aerodynamic performance of exhaust silencers. Power loss ratio is an important parameter to characterize the aerodynamic matching performance of exhaust silencers and reciprocating internal combustion engines, whereas resistance coefficient which is closely related to pressure loss is to characterize the aerodynamic performance of the exhaust silencer itself and is irrelevant with the reciprocating internal combustion engine on which the exhaust silencer is installed. The matching parameters of the sound power level of exhaust noise, the insertion loss, and the power loss ratio are used in this document as the measurement parameters.

For sound power level of exhaust noise, the measurement results at 90° direction and 45° direction can be different. The measurement results at 45° direction is slightly greater than the actual value, the measurement results at 90° direction is much closer to the actual results. For insertion loss, the measurement results at 90° direction and 45° direction may be different, but the measurement uncertainty at 90° direction is smaller than that at 45° direction. Measurement at 90° direction is used for the laboratory measurement (engineering method). The measurement at 90° or 45° direction is used for laboratory measurement (survey method). The measurement at 45° direction is used for site measurement.

1 Scope

This document specifies a measurement method and requirements for exhaust silencers which are installed on reciprocating internal combustion engines, including laboratory measurement and site measurement.

This document applies to all exhaust silencers installed on reciprocating internal combustion engines falling within the field of application of ISO 3046 1 . This document can also apply to other exhaust silencers for which no suitable International Standard exists.

NOTE Throughout the text, exhaust silencer is referred to as silencer and reciprocating internal combustion engine as engine.

2 Normative references

3 Terms and definitions

4 Test environment

4.1 General

4.2 Criteria for background noise

4.3 Criterion for acoustic adequacy of test environment

5 Instrumentation

5.1 General

5.2 Calibration

5.3 Use

6 Installation and operation of noise source under test for laboratory measurement

6.1 General

6.2 Source location

6.3 Installation requirements

6.4 Operation condition

7 Measurement

7.1 General

7.2 Measurement uncertainty

7.3 Laboratory measurement

7.4 Site measurement

8 Calculation

8.1 General

8.2 Calculation of sound power level of exhaust noise

8.3 Calculation of insertion loss

8.4 Calculation of power loss ratio

9 Information to be recorded

9.1 General

9.2 Description of the tested exhaust silencer and substitution pipe

9.3 Description of the engine on which the exhaust silencer is installed

9.4 Acoustic environment

9.5 Description of instrumentation

9.6 Acoustical data

10 Test report

Bibliography