Hello All,
The well known formula to calculate the acoustic impedance is Z=pV [p=density, V=acoustic velocity].
Also, the sound wave velocity can be calculated using V=sqrt(E/p) [E=Elastic modulus, p=density].
If the velocity from the second equation plugs into the first equation it becomes, Z=sqrt(pE) [p=density, E=Elastic modulus].
Is this a correct formula to drive? Are both of the first and third formulas correct to use?
Thanks,
Hamed
A more general definition of acoustic impedance is
Z= p/V where p is the pressure and V is the acoustic velocity.
The formula given by Abdolrasol is right only for plane waves.
As said by Claude, Z=p/V and for the case of a plane wave in a fluid |Z|=rho*c (rho=density and c= sound velocity) in absolute value.
See the french wiki page : https://fr.wikipedia.org/wiki/Imp%C3%A9dance_acoustique
We can start from displacement y=a sin(kx -wt). Then particle velocity dy/dt=u=-aw cos(kx-wt) and pressure in terms of bulk modulus kappa is p= kappa dy/dx= -kappa k a cos(kx -wt). Then using definition: acoustic impedance = p/u= kappa k/w. Now propagation velocity of the (phase of a monochromatic) wave is v where v2= kappa/rho, or, kappa= rho v2. Again phase velocity v= w/k, then acoustic impedance = kappa k/w= rho v2/ v= rho v.
Hello, Hamed
FOR THE CORRECT ANSWER, YOU MUST REFINE.
1. WHAT IMPEDANCE DO YOU WANT TO GIVE - PURE ACOUSTIC, WAVE INPEDANCE, IMPEDANCE OF RADIATION.
2. FOR WHAT TYPES OF ACOUSTIC WAVE YOU WANT INVESTIGATE YOUR PROBLEM (PLANES, SPHERICALS, CYLINDRICALS WAVES)?
IN YOUR CASE YOU . OBVIOUSLY. MIXING CONCEPTS - PHASE SPEED AND OSCILATIN SPEED
REQUIRED UPDATES
BYE
Hi,
Mr. Alexey made correct statement, however first equation seems general.
Regards,
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