Sound pressure

That Sound pressure (Symbol ) is in that the most important linear Sound field size.

Table of contents

Definition

As sound pressure the pressure fluctuations of a compressible sound transmission medium become (usually arise, designation. These pressure fluctuations become of als in motion for hearing feeling converted. If it concerns audible sound, these movements can then by that (hearing brain system) to be noticed. The sound pressure p thus the change pressure (a wechselgroesse) is, that the static ( with the unit symbol Pa. A Pascal corresponds to a pressure of one per square meter:

<math>

1 \ \mathrm{Pa} = 1 \ \frac{\mathrm{N}}{\mathrm{m^{2}}} = \frac{1 \ \mathrm{kg}}{\mathrm{m} \cdot \mathrm{s^{2}}} </math>

The sound pressure becomes usually as level size (s. usually.

It concerns with the sound one Clay/tone, thus a harmonious oscillation (often also as "SineOscillation "marks) with only one <math>f</math>, thus arises:

<math>

p(t) = \hat{p} \sin (2\pi ft) = \hat{p} \sin (\omega t) </math>

whereby <math>\hat{p}</math> those Sound pressure amplitude and ? those <math>\omega = 2 \cdot \pi \cdot f</math> is.

The sound pressure p takes in Direktfeld (Freifeld) and in Space sound field (Diffusfeld) in reverse proportionally to r from a punctiform acoustic source to that 1rLaw (Spacer law) off:

<math>

p \propto \frac{1}{r} </math>

<math>

\frac{p_1} {p_2} = \frac{r_2}{r_1} </math>

<math>

p_1 = p_{2} \cdot r_{2} \cdot \frac{1}{r_1} </math>

(note: The square Sound energy sizes, like z.B. those Loudness take with 1r2 over the distance off.)

As one can recognize here, absolutely the indication of the situation of the measuring point is necessary for the evaluation of an acoustic source apart from the indication of the measured sound pressure.

In the reverberation chamber this sound pressure acceptance is made by the distance less strongly, because it is affected by overlaying reflections. That distance of the acoustic source, with the one equality of Direct sound D too Space sound R prevails, thus the relationship D/R = 1 is, becomes Resounding radius rH called.

Connection with other acoustic sizes

The sound pressure p is with the acoustic sizes Z, Pak, v and Loudness I links as follows:

<math>

p = Z \cdot v = \frac{I}{v} = \sqrt{I \cdot Z} = \frac{P_{ak}}{v \cdot A} = \sqrt{\frac{P_{ak} \cdot Z}{A}} = {\xi \cdot Z \cdot \omega} = \frac{a \cdot Z}{\omega} = \frac{a \cdot Z}{\omega} = C \cdot \sqrt{\rho \cdot E} </math>.

Here is:

Symbol Units Meaning
p Sound pressure
f
? Sound deflection
C m/s
v m/s
<math>\omega</math> 1s
? /3 Atmospheric pressure (density of the medium)
Z = C ·? ·s/3 Sound radiation impedance, acoustic field impedance
A /s2 Sound acceleration
I /2 Loudness
E ·s/3 Schallenergiedichte
Pak
A 2 Durchschallte

Literature

  • Breuer, Hans: Dtv Atlas physics, volume 1. Mechanics, acoustics, thermodynamics, optics. Munich: Dtv publishing house, 1996, ISBN: 342303226X
  • Kuttruff, Heinrich: Acoustics. Stuttgart: Hirzel, 2004, ISBN: 3777612448
  • Mueller, Gerhard; Moeser, Michael: Paperback of the technical acoustics. Berlin: Springer, 3., erw. u. over work. Aufl. 2003, ISBN: 3540412425
  • Veit, Ivar: Technical acoustics. Peppering castle: Bird publishing house, 2005, ISBN: 3834330132

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