BS 7721(1994) : 1994 AMD 14748

Committees responsible
National foreword
Introduction
Method
1 Scope
2 Normative references
3 Definitions
4 Acoustic environment
5 Instrumentation
6 Object under test and test conditions
7 Sound pressure levels on the measurement surface
8 Calculation of surface pressure level, sound power
     level and directivity factor
9 Information to be recorded
10 Test report
Annexes
A (normative) Qualification procedures for the
     acoustic environment
B (informative) Examples of suitable instrumentation
     systems
C (informative) Calculation of directivity index and
     directivity factor using a hemispherical microphone
     array
D (informative) Bibliography
Tables
1 International Standards specifying various methods
     for determining the sound power levels of machines
     and equipment
2 Limits for correction
3 Uncertainty in determining sound power levels,
     expressed as the largest value of the standard
     deviation
4 Correction for background noise
Figures
1 Identification of the principal noise sources
2 Microphone locations (9 positions) and measurement
     surface for small gas turbine sets
3 Microphone locations and measurement surface for
     medium-sized gas turbine sets
4 Microphone locations for large gas turbine sets
5 Measurement surface and microphone positions for
     measuring the intake-inlet noise when no reflecting
     plane exists
6 Measuring surface and microphone positions for
     measuring the intake-inlet noise emitted from inlet
     systems of the gas turbine
7 Measurement surface and microphone positions for
     measuring exhaust-outlet noise when no reflecting
     plane exists
8 Measurement surface and microphone positions for
     measuring exhaust-outlet noise when b/a < 1,5
9 Measurement surface and microphone positions for
     measuring exhaust-outlet noise when b/a > 1,5
A.1 Environmental correction K, in decibels

Specifies methods for measuring the sound pressure levels on a measurement surface enveloping a source, and for calculating the sound power level produced by the source. Applies to gas turbines and gas turbine sets for: installation on board ships, or offshore installations, road and railway vehicles; industrial applications. Does not apply to gas turbines in aircraft applications. Coverage includes definitions, acoustic environment and instrumentation. Also includes detailed diagrams, tables and annexes.