ASTM_E_2459_-_05_2011.pdf

Designation:E245905(Reapproved 2011)Standard Guide forMeasurement of In-Duct Sound Pressure Levels from LargeIndustrial Gas Turbines and Fans1This standard is issued under the fixed designation E2459;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This guide is intended to provide a simple and consistentprocedure for the in-situ field measurement of in-duct soundpressure levels in large low pressure industrial air ducts,suchas for gas turbines or fans,where considerations such as flowvelocity,turbulence or temperature prevent the insertion ofsound pressure sensors directly into the flow.This standardguide is intended for both ambient temperature intake air andhot exhaust gas flow in ducts having cross sections of four(4)square meters,or more.1.2 The described procedure is intended to provide a repeat-able and reproducible measure of the in-duct dynamic pressurelevel at the inlet or exhaust of the gas turbine,or fan.The guideis not intended to quantify the“true”sound pressure level orsound power level.Silencers,as well as Waste Heat Boilers,must be designed using the in-duct sound power level as thebasis.Developing the true sound power level based on in-ductmeasurements of true sound pressure within a complete oper-ating system is complex and procedures are developmental andoften proprietary.1.3 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.Extreme caution ismandatory when working near hot exhaust gas systems andappropriate safety precautions such as the installation of quickacting isolation valves are recommended.2.Referenced Documents2.1 ASTM Standards:2C634 Terminology Relating to Building and EnvironmentalAcoustics2.2 ANSI Standards:S1.4 Specification for Sound Level Meters3S1.43 Specification for Integrating Averaging Sound LevelMeters33.Terminology3.1 Definitions of the acoustical terms used in this guide aregiven in Terminology C634.3.2 Definitions of Terms Specific to This Standard:3.2.1 anechoic tubea constant diameter tube of sufficientlength that a sound wave reflected from the far end of the tubetermination arrives at the microphone position sufficientlyattenuated that it will not appreciably affect the microphonereading.3.2.2 dynamic pressurethe total instantaneous pressureincident upon the opening of the test port,including theinfluence of convective turbulence,local tangential modes,localized boundary layer effects at the test port and theindeterminate effects of all duct acoustical modes.3.2.3 fixturethe apparatus containing the microphone fit-ting which locates the microphone flush with the insidediameter of the anechoic tube,the necessary fittings permittingairtight connection of the fixture and anechoic tube to the testport,and the anechoic tube.3.2.4 probe microphonea commercially available micro-diameter microphone probe that is inserted into the anechoictermination near the test port connection.Some probes requirea pressure compensation connection.Use and installation shallfollow manufacturers procedures/instructions.3.2.5 test portthe hole in the duct wall to which theanechoic tube is connected and whose diameter is equal to theinside diameter of the anechoic tube.In general the term testport,as used herein,will usually include any semi-permanentlyinstalled hardware in the wall of the duct permitting closure ofthe test port when not in use(ball valve and threaded pipe cap,or both)as well as the pipe elements permitting attachment ofthe fixture and the anechoic tube.1This guide is under the jurisdiction of ASTM Committee E33 on Building andEnvironmentalAcoustics and is the direct responsibility of Subcommittee E33.08 onMechanical and Electrical System Noise.Current edition approved April 1,2011.Published August 2011.Originallyapproved in 2005.Last previous edition approved in 2005 as E245905.DOI:10.1520/E2459-05R11.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.3Available from American National Standards Institute(ANSI),25 W.43rd St.,4th Floor,New York,NY 10036,http:/www.ansi.org.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 4.Summary of Guide4.1 Key features of this guide:4.1.1 Athrough-wall test port opening,25.4 mm(nominally,1 in.)or less,to which is connected the fixture,having aconstant inside diameter tube,to which the anechoic tube isconnected.The test po