哈工程振动噪声--第7章-机械噪声的分析测量和控制

page1授课人——柳贡民2021年1月21日星期四动力与能源工程学院CollegeofPowerandEnergyEngineeringChapter7NoiseAnalysis,Measurement,andControl第7章机械噪声的分析测量和控制page2授课人——柳贡民2021年1月21日星期四动力与能源工程学院CollegeofPowerandEnergyEngineeringTheroot-meansquare(rms)soundpressureCombinedsoundpressureofp1andp2TTedtppTdtpTp022102211TTTdtppTdtpTdtpT021022022111TeedtppTpp0212221222211121coscostptppppmmChapter7NoiseAnalysis,Measurement,andControl7.1CombinationofSoundLevels1111cosmppt2222cosmpptpage3授课人——柳贡民2021年1月21日星期四动力与能源工程学院CollegeofPowerandEnergyEngineering121211220022cos()cos()TTmmppdtppttdtTT121212121201cos()cos()TmmppttttdtT12121201cos[()()]TmmpptdtT(1)两列频率相同且以恒定相位差相交的单频率噪声声波的叠加21tconstan21)cos(21221021mmTppdtppTmepp22)cos(21221eepp相干波：频率相同、相位差固定不变的波称为相干波。Chapter7NoiseAnalysis,Measurement,andControl7.1CombinationofSoundLevelspage4授课人——柳贡民2021年1月21日星期四动力与能源工程学院CollegeofPowerandEnergyEngineering)cos(2122122212eeeeeppppp021if2212eeepppmmpp2112eeppif212212eeepppmmpp210ep这两种情况下的平均声能密度分别为12121220020eeppc1212122002eeppcChapter7NoiseAnalysis,Measurement,andControl7.1CombinationofSoundLevelspage5授课人——柳贡民2021年1月21日星期四动力与能源工程学院CollegeofPowerandEnergyEngineering(2)两列不相干噪声声波的叠加22212eeeppp'12'020TppdtT21orthefrequencyissame,butthephaseanglevariationisofrandom02021TdtppTTimeislongenough21两列具有不同频率，或频率相同但相交时相位差无规律变化的噪声声波叠加后的合成声场，其平均声能量密度等于每列噪声声波平均能量密度之和，这两列噪声波称为不相干波，它们的合成声场将遵守“能量相加法则”。Chapter7NoiseAnalysis,Measurement,andControl7.1CombinationofSoundLevelspage6授课人——柳贡民2021年1月21日星期四动力与能源工程学院CollegeofPowerandEnergyEngineeringNoiseisemittedusuallyfrommorethanonesourceoratdifferentfrequencies,anditisnecessarytocalculatethecumulativeoroverallsoundlevels.Obviously,sincethesoundlevelscalesarelogarithmic,theycannotbeaddedalgebraically.CombiningofsoundlevelsmaybeperformedusingtheenergyadditiontheoremandtheoveralllevelL(OA)isdeterminedbyHere,eachsoundleveltobecombinedmightbethenoisefromnindividualsourcesorthesoundlevelsassociatedwithnoctavebands.Theymaybesoundpowerlevelsorsoundpressurelevels.niLiOAL110/10lg10)(Chapter7NoiseAnalysis,Measurement,andControl7.1CombinationofSoundLevelspage7授课人——柳贡民2021年1月21日星期四动力与能源工程学院CollegeofPowerandEnergyEngineering222221eneeepppp22222221lg10lg10)(reneereppppppOAL221010reiippL22lg10reippLiniLniireippOAL11012210lg10lg10)(Chapter7NoiseAnalysis,Measurement,andControl7.1CombinationofSoundLevelspage8授课人——柳贡民2021年1月21日星期四动力与能源工程学院CollegeofPowerandEnergyEngineering122222eeeennppppChapter7NoiseAnalysis,Measurement,andControl7.1CombinationofSoundLevels设有n个不同频率，或频率相同但相位差无规律变化的噪声源，则其平均声压级可推导得到1222222222eeeenrrrrppppnpppp122222222222111()eeeeneinirrrrrppppppnpppnp21021110log10log(10)ieLnpirpLpnpage9授课人——柳贡民2021年1月21日星期四动力与能源工程学院CollegeofPowerandEnergyEngineeringL1-L2012345678910Lc-L13.02.52.11.81.51.21.00.80.60.50.4Anothereasyandusefulmethodforcombiningsoundlevelsistoutilizethetableasbellow.Thecombinedeffectofsoundsdependsonthedifferenceintheirdecibellevels.实际计算表明，两列声压级相同的噪声叠加后，总声压级仅增加3dB；两列噪声的声压级相差10dB以上，则声压级低的那列噪声对总声压级的贡献可以忽略不计，总声压级近似等于声压级高的那个值.Chapter7NoiseAnalysis,Measurement,andControl7.1CombinationofSoundLevelspage10授课人——柳贡民2021年1月21日星期四动力与能源工程学院CollegeofPowerandEnergyEngineering(1)OctaveBandand1/3OctaveBandSpectralAnalysisInnoisecontrolengineering,thebandsarerelatedbythefollowingrelationshipnluff2n=1,octavebandn=1/3,one-third-octavebandThecenterfrequencyofanysuchbandisdefinedasthegeometricmeanulcfffThelowerandupperlimitfrequenciesmaybedeterminedfromthecenterfrequencyas22nlcff22nucffChapter7NoiseAnalysis,Measurement,andControl7.2SpectralAnalysisofNoisepage11授课人——柳贡民2021年1月21日星期四动力与能源工程学院CollegeofPowerandEnergyEngineeringOctaveBand1/3OctaveBandLowerLimitFrequency(Hz)CenterFrequency(Hz)UpperLimitFrequency(Hz)LowerLimitFrequency(Hz)CenterFrequency(Hz)UpperLimitFrequency(Hz)2231.54422.42528.228.231.535.535.54044.744638844.75056.256.26370.870.88089.18812517789.1100112112125141141160178177250355178200224224250282282315355355500710355400447447500562562630708Chapter7NoiseAnalysisandMeasurement7.2SpectralAnalysisofNoisepage12授课人——柳贡民2021年1月21日星期四动力与能源工程学院CollegeofPowerandEnergyEngineering7101,0001,4207088008918911,0001,1221,1221,2501,4131,4202,0002,8401,4131,6001,7781,7782,0002,2392,2392,5002,8182,8404,0005,6802,8183,1503,5483,5484,0004,4674,4675,0005,6235,6808,00011,3605,6236,3007,0797,0798,0008,9138,91310,00011,22011,36016,00022,72011,22012,50014,13014,13016,00017,78017,78020,00022,390Chapter7NoiseAnalysisandMeasurement7.2SpectralAnalysisofNoisepage13授课人——柳贡民2021年1月21日星期四动力与能源工程学院CollegeofPowerandEnergyEngineering(1)OctaveBandand1/3OctaveBandSpectralAnalysisBandNumber12345678CenterFreq.(Hz)631252505001000200040008000SPLat3ft(dB)1261321281191151089890133134.3134.4OverallSPL134dBChapter7NoiseAnalysisandMeasurement7.2SpectralAnalysisofNoise128.5115.898.6115.9L1-L2012345678910Lc-L13.02.52.11.81.51.21.00.80.60.50.4page14授课人——柳贡民2021年1月21日星期四动力与能源工程学院College