BS 5944-4:1984

Foreword
Committees responsible
Method
0 Introduction
1 Scope
2 Definitions
3 Measurement uncertainty
4 Test environment
5 Instrumentation
6 Installation conditions for valve
7 Operating conditions
8 Location and number of sound measurement points
9 Test procedure
10 Calculation of valve mean sound pressure levels and
    sound power levels
11 Calculation of mean sound pressure level at a
    reference distance
12 Information to be recorded
13 Test report
14 Identification statement
Appendices
A Guidance on valve instability and its detection
B Guidance on measuring in an anechoic chamber
C Errors and classes of measurement
Tables
1 Standard deviation of sound power level
    determination
2 Environmental qualification procedures
3 Flow settings
4 Pressure settings
5 Limit of variations in test conditions
6 Permissible systematic errors of measuring
    instruments as determined during calibration
Figures
1 Example of test installation in an anechoic chamber
2 Relationship between the reference box and
    hemispherical measurement surface
3 Coiling of return hose

Describes procedures for the determination of sound power levels of a hydraulic fluid power valve under controlled conditions of installation and operation, suitable for providing a basis for comparing the noise levels of valves.

This British Standard describes procedures for the deter-mination of the sound power levels of a hydraulic fluid power valve, under controlled conditions of installation and operation, suitable for providing a basis for comparing the noise levels of valves in terms of:

1. A-weighted sound power level;
2. octave band sound power levels.

From these sound power levels, reference sound pressure levels may be calculated for reporting purposes (see clause 11). For general purposes, the frequency range of interest includes the octave bands with centre frequencies between 125 Hz and 8000 Hz.

This method is applicable to all types of fluid power control valves operating with oil hydraulic fluids^* under steady state conditions, irrespective of size or specific function, provided that the noise level measured is dominantly cavitation noise and the physical provisions of the method can be complied with.

The procedures described are intended to measure the airborne noise level obtainable from a valve installation representing good noise control practice, including valve casing noise and the noise radiated by flexible fluid lines immediately adjacent to the valve. Other systems depen¬dent factors are eliminated.

The measurement of valve noise due to instability is specifically excluded from the provisions of this standard. Guidance on valve stability and its detection is given in appendix A. Guidance is also given in appendix B on measuring in an anechoic chamber.

Accuracy of measurement is divided into three classes, A, B and C, which are explained in appendix C.

NOTE. The titles of the publications referred to in this standard are listed on the inside back cover.

^* e.g. hydraulic fluid designations L-HH, L-HL, L-HM, L-HR, L-HV and L-HG only as classified in BS 6413 : Part 4.