Acoustic velocity
Those Acoustic velocity, symbols <math>\vec v</math>, indicates, with which the air particles (and/or Particle the sound transmission medium) around their rest position swing; thus the momentary speed of a swinging particle. The acoustic velocity is in that a linear, Sound field size, those often briefly as "Snaps"one designates and one indicates in m/s. It computes itself as that Deflection <math>\vec \xi</math> the particle after the time:
<math>{\vec v} = \frac{d{\vec\xi}}{dt} = \dot\vec \xi </math>
The acoustic velocity may not however with that C, the propagation speed of the acoustic waves in the transmitting medium to be thus confounded, although both are measured in m/s.
For numerical value data of the acoustic velocity usually that becomes Rms of the consulted. Usual is besides an indication as Level value:
- <math>
L_v = 20 \, \log_{10}\left(\frac{v_1}{v_0}\right)dB </math> .
v1 stands here for the rms (measured) snaps, v0 for the reference value. The reference value became by standardization up
- <math>
v_0 = 5.0 10^{-8 \cdot} \frac{m}{s} </math>
specified.
The acoustic velocity v in m/s is with even progressive Acoustic waves:
- <math>
v = \frac{p}{Z} = \frac{I}{p} = \sqrt \frac{I}{Z} = \xi \cdot \omega = \frac{a}{\omega} = \sqrt \frac{E}{\rho} = \sqrt \frac{P_{ak}}{Z A \cdot} </math>
Here the symbols stand for the following sizes:
| Symbol | Units | Meaning |
|---|---|---|
| v | m/s | Acoustic velocity |
| p | = N/m2 | Sound pressure |
| Z = C ·? | ·s/3 | Sound radiation impedance, acoustic field impedance |
| I | /2 | Loudness |
| ? | , | Sound deflection |
| <math>\omega</math> = 2 · <math>\pi</math> · f | /s | |
| A | /s2 | Sound acceleration |
| ? | /3 | Atmospheric pressure, density of air (the medium) |
| f | ||
| E | ·s/3 | Schallenergiedichte |
| Pak | , | |
| A | 2 | Durchschallte |
| C | /s |
The acoustic velocity is over those Euler equation with that Sound pressure linked. This becomes z.B. with the regulation that Loudness, the product of acoustic velocity and sound pressure (s. there), used. With an even progressive wave are acoustic velocity and sound pressure.
The measurement of the acoustic velocity becomes difficult, because a diaphragm is used like it in microphones, the movement of the air particles inertialess follows and therefore to be practically massless would have. Small band microphones very small diaphragm masses reach and can be seen therefore with restrictions as acoustic velocity receivers. Hot wire microphones permit the collection of the rms to the acoustic velocity in certain directions, do not show however the acoustic signal not.
See also:
Sound deflection | Particle displacement | Sound field size | Sound acceleration | Sound pressure | Loudness | Schallenergiedichte | | Even wave | Kugelwelle | Near field | Far field |
Or also the levels:
| Acoustic velocity level | Loudness level | Sound-power level |
