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Published byMarsha Harrington Modified over 9 years ago
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ACOUSTIC THEORY WAVE VELOCITY ACOUSTIC IMPEDANCE REFLECTION AND TRANSMISSION REFRACTION RADIATION ATTENUATION
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Gases : Liquids : Solids : B = modulus bulk = compressibility Y = Young modulus = Poisson ratio = specific heat ratio o = mass density P p = pressure ACOUSTIC WAVE VELOCITY Sound velocity, speed of sound (SOS) Depend on the medium/material properties c solid > c liquid > c gas
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ACOUSTIC IMPEDANCE Defined by the ratio of acoustic pressure and particle velocity Z = c GasTemperature [ o C] Mass Density [kg/m 3 ] Wave Velocity [m/s] Acoustic Impedance [Rayls] Air01,293331,5428 Air201,21343415 O2O2 01,43317,2512 CO 2 01,98258532 H2H2 00,091269,5114 Steam1000,6404,8242 Wave velocity and acoustic impedance in gases
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LiquidTemperature [ o C] Mass Density [kg/m 3 Velocity [m/s] Acoustic Impedance [MRayls] Water2099814811,48 Water13102615001,54 Alcohol2079011500,91 Oil2095015401,46 Mercury2013600145019,72 Glyserin20126019802,50 Wave velocity and acoustic impedance in liquids
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SolidVelocity [ o C] Mass Density [kg/m 3 Acoustic Impedance [MRayls] Rubber110024002,64 Plastic118026703,15 Copper8900500044,5 Steel7800585045,63 Aluminum2700630017,01 Concrete260031008,06 Wood45035001,58 Wave velocity and acoustic impedance in solids
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REFLECTION AND TRANSMISSION PiPi PrPr PtPt First medium Z 1 Z 2 Second medium R = Reflection factor T = Transmission factor
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R = Power reflection coefficient T = Power reflection coefficient Acoustic Intensity :
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PiPi PrPr PtPt First medium Z 1 Z 2 Second Medium x ii rr tt REFRACTION Critical angle :
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D N Fraunhofer zoneFresnel zone WAVE RADIATION N = Near field length D = Transducer diameter = Wave length
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ATTENUATION x IoIo I I o = Initial intensity I = Intensity after propagation = Coefficient of attenuation
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