朗德科技声学测试培训.ppt

Highfrequencycomponentscouldgothroughsmallholesminimizinganyinsulationinstallation!!(holedimensiondl).高频成分更容易穿过小孔（dl）lddlSddlSldAllthesoundthroughtheapertureistransmitted.(TL=0,TransmissionLoss,Transmissioncoefficientt=1)通过小孔的声音被完全传播(TL=0，传播系数t=1)Example:Diffusionofsound(soundpassesthroughholes)例：声音的散射（声音通过小孔传播）Thesoundwillpassthroughtheholere-radiatedinanomnidirectionalwaysimilartotheoriginalbutTLisnotzero.Thesoundpowertransmittedisfarless(t1).声音通过小孔发散，像初始声源一样，但是TL≠0，声能大大减小。adSWWTFrequencydecompositionofsoundisveryimportantbecause:声音的频率分析非常重要，因为：Theauditorysystemsensitivityvarieswithfrequencies听觉系统的灵敏度会随着频率的不同发生变化Speechrange:200Hz---6000Hz语音频率范围：200Hz---6000HzSpeechintelligibilityrange:500Hz---4000Hz清晰语音频率范围：500Hz---4000HzMaterialThicknessIncludinganyairspace(mm)Frequency(Hz)631252505001000200040008000Brickwork_0.050.050.040.020.040.050.050.05Polishedmarble_0.010.010.010.010.010.010.010.01Glassorrockwool(mediumdemsity)250.050.100.350.600.700.750.800.75Thickpilecarpetonspongerubberunderlay150.050.150.250.500.600,700,700.65Typicalabsorptioncoefficientsfor4materials4种典型材料的吸声系数（吸声系数——用以表征材料和结构吸声能力的基本参量）Frequencydecompositionofsoundisveryimportantbecause:声音的频率分析非常重要，因为：Thenoisepropagationvarywithfrequencieswithinaclosedspace在封闭的空间内，声音的传播随频率变化Propagationofwavesinsidearoomwillbedifferentaccordingtofrequencies:室内声波的传播随着频率的不同而变化：Someofwavesfromasourceinsideanenclosurewillreflectedonthewallandwillbebackatanypointinphase在密闭空间里，部分声波被墙壁反射，并以不同相位反射 amplificationofthewavedisturbance对声波的幅值进行增益 Normalmodewillberesonant引起固有振荡Whenfrequencyofthesource=resonancefrequencyofanormalmodeofroom当声源频率=室内固有振荡的频率时 resonanceoccursroomrespondsstrongly(spatialdistributionofpressurecharac