SIST EN ISO 7235:1997

Acoustics - Measurement procedures for ducted silencers - Insertion loss, flow noise and total pressure loss (ISO 7235:1991)

This International Standard specifies the substitution method for determining the insertion loss of ducted silencers. It sets out requirements for determining:  - the insertion loss, in frequency bands, of silencers with and without air flow;  - the sound power level, in frequency bands, of the flow noise generated by silencers;  - the total pressure loss of silencers with air flow.  The measurement procedures are intended for laboratory measurements on silencers but may also be used for in situ measurements on silencers if the requirements of this International Standard can be met.  This International Standard applies to silencers for ventilating air-conditioning systems which are usually connected to ducts or splitter absorbers mounted in ducts. Other duct elements, such as bends or T-connectors, may also be tested using this Intenational Standard.  This International Standard does not apply to reactive silencers used for motor vehicles.  [There is a note on the precision of the method]

Akustik - Messungen an Schalldämpfern in Kanälen - Einfügungsdämpfungsmaß, Strömungsgeräusch und Gesamtdruckverlust (ISO 7235:1991)

Diese internationale Norm beschreibt das Substitutionsverfahren zur Bestimmung des Dämpfungsverlustes von Schalldämperfn in Kanälen. Sie trifft Festlegungenzur Bestimmung - des Einfügungsdämpfungsmaßes von Schalldämpfern mit und ohne Luftstrom, gemessen in Frequenzbändern - des Schalleistungspegels des Strömungsgeräusches, verursacht durch Schalldämpfer, gemessen in Frequenzbändern - des Gesamtdruckverlustes von luftdurchströmten Schalldämpfern.

Acoustique - Méthodes de mesurage pour silencieux en conduit - Perte d'insertion, bruit d'écoulement et perte de pression totale (ISO 7235:1991)

Akustika - Merilni postopki za dušilnike za kanale - Dodano dušenje, hrup zaradi pretoka in padec totalnega tlaka (ISO 7235:1991)

General Information

• Status: Withdrawn
• Publication Date: 31-Mar-1997
• Withdrawal Date: 31-Dec-2003
• ICS: 17.140.01 - Acoustic measurements and noise abatement in general
• ICS: 91.120.20 - Acoustics in building. Sound insulation
• ICS: 91.140.30 - Ventilation and air-conditioning systems
• Technical Committee: AKU - Acoustics
• Current Stage: 9900 - Withdrawal (Adopted Project)
• Start Date: 01-Jan-2004
• Due Date: 01-Jan-2004
• Completion Date: 01-Jan-2004
• Directive: 89/392/EEC - Machinery - Safety of machinery: general essential health and safety requirements
• Directive: 98/37/EC - Machinery
• Mandate: M/BC/CEN/88/13 - Standardization request to CEN/CENELEC relating to machinery
• Ref Project: EN ISO 7235:1995 - Acoustics - Measurement procedures for ducted silencers - Insertion loss, flow noise and total pressure loss (ISO 7235:1991)

Relations

• Replaced By: SIST EN ISO 7235:2004 - Acoustics - Laboratory measurement procedures for ducted silencers and air-terminal units - Insertion loss, flow noise and total pressure loss (ISO 7235:2003)
• Effective Date: 01-Jan-2004

Standards Content (Sample)

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Akustika - Merilni postopki za dušilnike za kanale - Dodano dušenje, hrup zaradi pretoka in padec totalnega tlaka (ISO 7235:1991)Akustik - Messungen an Schalldämpfern in Kanälen - Einfügungsdämpfungsmaß, Strömungsgeräusch und Gesamtdruckverlust (ISO 7235:1991)Acoustique - Méthodes de mesurage pour silencieux en conduit - Perte d'insertion, bruit d'écoulement et perte de pression totale (ISO 7235:1991)Acoustics - Measurement procedures for ducted silencers - Insertion loss, flow noise and total pressure loss (ISO 7235:1991)91.140.30VLVWHPLVentilation and air-conditioning91.120.20L]RODFLMDAcoustics in building. Sound insulation17.140.01Acoustic measurements and noise abatement in generalICS:Ta slovenski standard je istoveten z:EN ISO 7235:1995SIST EN ISO 7235:1997en01-april-1997SIST EN ISO 7235:1997SLOVENSKI
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ISO 7235:1991 (E) A-A Mineral wo01 Petforated sheet L L *Sd e - H=2000mm Figure D.4 - Example of two-sided anechoic termination [tested for d = 400 mm, d = 500 mm (see [13j) and d = 630 mm] 23 SIST EN ISO 7235:1997



ISO 7235:1991 (E) 1 2 3 4a 4b 5 6 7 8 9 10 Annex E (informative) Examples of measurement arrangements \ / 4 I 2 A 6 \ / V 5 ? /’ Loudspeaker unit Test duct in frontof the test silencer Transition eiements Test silencer Substitution duct Test duct behind the test silencer Transmission element 1 (as an alternative to 10) Reverberation room Microphone positions behind the test silencer (as alternatives to 9) Microphone positions in the reverberation room (as alternatives to 8) Anechoic termination (as an alternative to 6 and 7) Microphone b O0 O0 positions Figure E.1 - Examples of arrangements for the test facility for measuring the insertion loss of a silencer without air flow by the Substitution method 24 SIST EN ISO 7235:1997



ISO 7235:1991 (E) a) Arrangement for in-duct measurements 7 1 (’ I t I &-y,:gy, 11 12 IO 13 1‘2 13 11 b) Arrangement when using a reverberation room 1 Loudspeaker unit in the Source chamber 10 Fan (instaiied to generate either forward or reversed 2 Test duct in front of the test siiencer fiow relative to the direction of Sound propagation) 3 Transition eiements 11 Fan siiencers 4a Test siiencer 4b Substitution duct 12 Flexible duct sections 5 Test duct behind the test siiencer 13 Vibration insuiation 6 Transmission eiement, also used as fiow diffuser 14 Nozzie for measurement of fiow rate (alternative: 7 Reverberation room orifice or venturi nozzie) 8 Wind-shieided microphones
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