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ACOUSTIC THEORY. WAVE VELOCITY ACOUSTIC IMPEDANCE REFLECTION AND TRANSMISSION REFRACTION RADIATION ATTENUATION. ACOUSTIC WAVE VELOCITY Sound velocity, speed of sound (SOS) Depend on the medium/material properties c solid > c liquid > c gas. = specific heat ratio
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ACOUSTIC THEORY • WAVE VELOCITY • ACOUSTIC IMPEDANCE • REFLECTION AND TRANSMISSION • REFRACTION • RADIATION • ATTENUATION
ACOUSTIC WAVE VELOCITY • Sound velocity, speed of sound (SOS) • Depend on the medium/material properties • csolid > cliquid > cgas • = specific heat ratio o = mass density Pp = pressure Gases : B = modulus bulk = compressibility Liquids : Y = Young modulus = Poisson ratio Solids :
ACOUSTIC IMPEDANCE • Defined by the ratio of acoustic pressure and particle velocity • Z = c Wave velocity and acoustic impedance in gases
REFLECTION AND TRANSMISSION Pt Pi Pr First medium Z1 Z2 Second medium R = Reflection factor T = Transmission factor
Acoustic Intensity : R = Power reflection coefficient T = Power reflection coefficient
REFRACTION Pi Pt r t x i Pr First medium Z1 Z2 Second Medium Critical angle :
WAVE RADIATION N D Fresnel zone Fraunhofer zone N = Near field length D = Transducer diameter = Wave length
ATTENUATION x Io I Io = Initial intensity I = Intensity after propagation = Coefficient of attenuation