NBN EN ISO 7235 : 2009

Foreword
Introduction
1 Scope
2 Normative references
3 Terms and definitions
4 Symbols
5 Test facilities and requirements for instrumentation
  5.1 Purpose and types of test facilities
  5.2 Equipment for acoustic testing of silencers
  5.3 Equipment for acoustic testing of air-terminal
      units
  5.4 Equipment for flow testing
  5.5 Equipment for dynamic testing
6 Test procedures
  6.1 General
  6.2 Insertion loss
  6.3 Transmission loss
  6.4 Sound power level of the flow noise (or regenerated
      sound)
  6.5 Volume flow rate and pressure loss coefficient
7 Information to be recorded
  7.1 Description of the test object
  7.2 Instrumentation
  7.3 Sound-source equipment
  7.4 Test, substitution and transmission ducts
  7.5 Transitions
  7.6 Anechoic termination
  7.7 Reverberation room
  7.8 Acoustical test results
  7.9 Measurement uncertainty
8 Information to be reported
Annex A (normative) Design of the sound field excitation
        equipment and qualification tests
Annex B (normative) Transmission element
Annex C (normative) Duct walls and limiting insertion
        loss
Annex D (normative) Conversion of one-third-octave-band
        attenuation values to octave-band attenuation
        values
Annex E (normative) Measurements on large parallel-baffle
        silencers
Annex F (normative) Test of longitudinal attenuation
Annex G (informative) Anechoic terminations
Annex H (informative) Examples of measurement
        arrangements
Bibliography

Specifies the substitution method for determining the insertion loss of ducted silencers. Sets out the requirements for determining: the sound power level, in frequency bands, of the flow noise generated by silencers; the insertion loss, in frequency bands, of silencers with and without air flow; the total pressure loss of silencers with air flow. Applies to silencers for ventilating and air-conditioning systems which are usually connected to ducts or splitter absorbers mounted in ducts.