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
Annex ZA (informative) - Relationship between this European Standard
                         and the Essential Requirements of EU
                         Directive 98/37/EC
Annex ZB (informative) - Relationship between this European Standard
                         and the Essential Requirements of EU
                         Directive 2006/42/EC
Bibliography

ISO 7235:2003 specifies methods for determiningthe insertion loss, in frequency bands, of ducted silencers with and without airflow,the sound power level, in frequency bands, of the flow noise (or regenerated sound) generated by ducted silencers,the total pressure loss of silencers with airflow, andthe transmission loss, in frequency bands, of air-terminal units.The measurement procedures are intended for laboratory measurements at ambient temperature. Measurements on silencers in situ are specified in ISO 11820.It is to be noted that the results determined in a laboratory according to ISO 7235:2003 will not necessarily be the same as those obtained in situ (installation), as different sound and flow fields will yield different results. For example, the pressure loss will be lower under laboratory conditions than in situ, but will be comparable between different laboratories.ISO 7235:2003 is applicable to all types of silencer including silencers for ventilating and air-conditioning systems, air intake and exhaust of flue gases, and similar applications. Other passive air-handling devices, such as bends, air-terminal units or T-connectors, can also be tested using this International Standard.It is not applicable to reactive silencers used for motor vehicles.