NF EN ISO 7235

NF EN ISO 7235

November 2009
Standard Current

Acoustics - Laboratory measurement procedures for ducted silencers and air-terminal units - Insertion loss, flow noise and total pressure loss

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.

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National standards and national normative documents

Publication date

November 2009

Number of pages

60 p.

Reference

NF EN ISO 7235

ICS Codes

17.140.01   Acoustic measurements and noise abatement in general
91.120.20   Acoustics in building. Sound insulation

Classification index

S31-127

Print number

1 - 18/11/2009

International kinship

ISO 7235:2003

European kinship

EN ISO 7235:2009
Sumary
Acoustics - Laboratory measurement procedures for ducted silencers and air-terminal units - Insertion loss, flow noise and total pressure loss

ISO 7235:2003 specifies methods for determining

  • the 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, and
  • the 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.

Replaced standards (1)
NF EN ISO 7235
February 2004
Standard Cancelled
Acoustics - Laboratory measurement procedures for ducted silencers and air-terminal units - Insertion loss, flow noise and total pressure loss

ISO 7235:2003 specifies methods for determining the 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.

Table of contents
  • Avant-propos
    iv
  • Introduction
    v
  • 1 Domaine d'application
    1
  • 2 Références normatives
    2
  • 3 Termes et définitions
    2
  • 4 Symboles
    7
  • 5 Installations d'essai et appareillage de mesure
    9
  • 5.1 But et types d'installations d'essai
    9
  • 5.2 Equipement pour l'essai acoustique des silencieux
    9
  • 5.3 Equipement pour l'essai acoustique des unités terminales
    15
  • 5.4 Equipement pour l'essai d'écoulement
    16
  • 5.5 Equipement pour essai dynamique
    21
  • 6 Modes opératoires d'essai
    22
  • 6.1 Généralités
    22
  • 6.2 Perte d'insertion
    22
  • 6.3 Perte de transmission
    24
  • 6.4 Niveau de puissance acoustique du bruit d'écoulement (ou bruit régénéré)
    24
  • 6.5 Débit-volume et coefficient de perte de pression
    25
  • 7 Informations à consigner
    29
  • 7.1 Description de l'objet en essai
    29
  • 7.2 Appareillage
    29
  • 7.3 Source sonore
    29
  • 7.4 Conduits de mesurage, de substitution et éléments de transmission
    30
  • 7.5 Pièces de raccordement
    30
  • 7.6 Terminaison anéchoïque
    30
  • 7.7 Salle réverbérante
    30
  • 7.8 Résultats de l'essai acoustique
    30
  • 7.9 Incertitude de mesure
    31
  • 8 Informations à fournir dans le rapport d'essai
    31
  • Annexe A (normative) Conception du dispositif d'excitation du champ acoustique et essais de qualification
    32
  • Annexe B (normative) Élément de transmission
    34
  • Annexe C (normative) Parois du conduit et perte limite d'insertion
    37
  • Annexe D (normative) Conversion des valeurs d'atténuation en bande de tiers d'octave en valeurs d'atténuation en bande d'octave
    40
  • Annexe E (normative) Mesurages sur des silencieux de grande taille à baffles parallèles
    41
  • Annexe F (normative) Essai relatif à l'atténuation longitudinale
    44
  • Annexe G (informative) Terminaisons anéchoïques
    45
  • Annexe H (informative) Exemples de dispositifs de mesure
    47
  • Bibliographie
    49
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