Acoustic efficiency

The acoustic efficiency , (Engl. Acoustic efficiency) is at the sound sources , the ratio between the recorded for the purpose of sound generating electrical or mechanical output and the radiated sound power. Analogous to the general efficiency , the acoustic efficiency is also designated with η ( Eta ) and, like this, can assume values ​​between 0 and 1 (corresponding to 0 to 100%).

${\displaystyle \eta ={\frac {P_{\mathrm {ak} }}{P_{\mathrm {el} }}}\,}$

With:

P _ak = given acoustic power

P _el = electrical or mechanical power consumed

In the case of devices, the purpose of which is not to generate sound, but in which the generated sound is an undesirable side effect, the ratio of the two powers is not called efficiency, but conversion rate . Machine noise is an example of this.

Examples of the acoustic efficiency of some sound sources

Sound source	Acoustic efficiency
Electric motor	10 −8
transmission	10 −7
fan	10 −6
Gas turbine	10 −5
Internal combustion engine	10 −4
Propeller plane	10 −3
speaker	10 −2
siren	10 −1

Of these sound sources, only the siren and the loudspeaker must necessarily emit high-level useful sound.

Specification of the acoustic efficiency for loudspeaker data

Acoustic efficiency η of a loudspeaker:

${\displaystyle \eta ={\frac {P_{\mathrm {ak} }}{P_{\mathrm {el} }}}\,}$

With:

P _ak = given acoustic power

P _el = supplied electrical power

The definition of the acoustic efficiency corresponds to that of the acoustic conversion efficiency.

In the loudspeaker data, the very low level of efficiency is never given as a percentage, but rather the characteristic sound pressure level in dB / W / m, which is incorrectly referred to as "efficiency". The efficiency is between 0.002 and 0.02 - so only between 0.2 and 2 percent. It can be converted into the characteristic sound pressure:

${\displaystyle {\text{Kennschalldruckpegel in dB}}=112+10\cdot \log _{10}({\text{Wirkungsgrad}})\,}$

See also

• Efficiency

literature

• G. Moschioni, B. Saggin: A new method for measurement of acoustic efficiency of classic guitars . In: Instrumentation and Measurement Technology Conference , 2004. IMTC 04. Proceedings of the 21st IEEE, Volume 3, Issue 18-20, May 2004, Vol. 3, pp. 1953-1958.
• Tomonao Okubo, Kohei Yamamoto: Procedures for determining the acoustic efficiency of edge-modified noise barriers . Kobayasi Institute of Physical Research, 3-20-41 Higashi-motomachi, Kokubunji, 185-0022 Tokyo, March 2006.

Individual evidence

1. ↑ tu-clausthal.de: Acoustic efficiency