BS EN 25136:1994
Superseded
A superseded Standard is one, which is fully replaced by another Standard, which is a new edition of the same Standard.
A superseded Standard is one, which is fully replaced by another Standard, which is a new edition of the same Standard.
Acoustics. Determination of sound power radiated into a duct by fans. In-duct method
Hardcopy , PDF
04-17-2003
English
02-15-1994
Cooperating organizations
National foreword
Foreword
Method
1. Scope
2. Normative references
3. Definitions and symbols
4. Test facilities and instrumentation
5. Test arrangements
6. Test procedure
7. Calculations
8. Information to be recorded
9. Information to be reported
Annexes
A. (normative) Computational procedures for calculating
A-weighted sound power level from octave or one-third
octave band power levels
B. (normative) Determination of the signal-to-noise
ratio of sound to turbulence noise in the test duct
C. (informative) Guidelines for the design and
construction of an anechoic termination
D. (informative) Evaluation of performance of anechoic
terminations
E. (informative) Example of a sampling tube
F. (informative) Measurement of the swirl component
G. (informative) Bibliography
Tables
1. Precision of the method of measurement
2. Cross-sectional areas of ducts
3. Maximum pressure reflection coefficients
4. Limiting values of the directivity constant K
5. Flow velocity correction, C3, in decibels, for the
frequency response of the sampling tube
6. Modal correction, C4, for the frequency response of
the sampling tube
7. Radial positions of the sampling tube
A.1 Values of Cj
B.1 Maximum allowable difference between the sound
pressure level readings of a microphone fitted with
a nose cone, LPNC, and of a microphone fitted with
a sampling tube, LPST, as a function of the
turbulence noise suppression delta Lt, of the
sampling tube, for a minimum signal-to-noise ratio
of sound to turbulence noise of 6 dB
E.1 Turbulence noise suppression, delta Lt, of the
typical sampling tube shown in figure E.1 as
compared with a 13 mm nose cone
Figures
1. Test arrangement and limiting dimensions of test
ducts, intermediate ducts and transitions
2. Limiting curves for the directivity of the sampling
tube (broad-band noise of one-third octave bandwidth)
3. Radial position of the sampling tube
C.1 Examples of anechoic terminations
C.2 Example of one-sided anechoic terminations
C.3 Example of anechoic termination
C.4 Example of two-sided anechoic termination
C.5 Examples of throttling sections
E.1 Schematic drawing of a typical sampling tube
E.2 Typical mountings of microphone and sampling tube
National annexes
NA (informative) Committees responsible
NB (informative) Cross-reference
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