Acoustic impedance
- Sound pressure
- SPL
- Sound velocity
- Schallauslenkung
- Sound acceleration
- Sound intensity
- Sound power
- Sound energy density
- Sound energy
- Sonic flow
- Acoustic impedance
- Speed of sound
Together with the acoustic impedance and the flow impedance of the mechanical characteristic acoustic impedance, also called acoustic impedance or field specific acoustic impedance, one of the three used in the acoustic impedance definitions. ZF is the acoustic impedance, the specific impedance is referred to as characteristic impedance of the medium.
The characteristic acoustic impedance is a physical quantity and is defined by the ratio of sound pressure to particle velocity. Your character formula is IF and their derived SI unit is Ns/m3. Acoustic resistance and acoustic resistance are obsolete names for the characteristic acoustic impedance. Another little physically meaningful label is sound hardness. Move sound waves from one medium to another ( eg from air to water ), so they (the water surface in this case) reflected at the boundary surface, the stronger the larger the difference of the characteristic acoustic impedances of the two media. The acoustic reflection coefficient is the ratio of sound pressure pr of the reflected wave at the boundary surface to the sound pressure of the incident pump wave. This is also the ratio of the difference between the two characteristic acoustic impedance to the sum of the characteristic acoustic impedance.
The acoustic reflection coefficient r is:
At normal sound incidence.
In the far field pressure and velocity are in phase, so the characteristic acoustic impedance calculated from real-valued
The constant of proportionality between the sound pressure and velocity is also referred to as impedance. The word " resistance " is the analogy to the electric resistance R = V / I signal because the voltage similar to the sound pressure is related to the power and speed with a particle stream.
The individual symbols stand for the following sizes:
The above equation shows that the product of density and velocity of sound is the characteristic acoustic impedance of the same, and thus in a homogeneous sound field is invariant in space and constant in time. This relationship is also called " ohmic law as acoustic equivalent ".
Temperature dependence in air
Air is the characteristic acoustic impedance ZF = 414 Ns/m3 at 20 ° C or at 25 ° C. 410 Ns/m3 As can be seen, this size is strongly temperature dependent.
Material dependence
(*) Physics textbook: Vol I: mechanics, acoustics, thermodynamics. Ernst Grimsehl, Walter Schallreuter. P.256.