Specific sound power level

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Physical size
Surname	Specific sound power level
Formula symbol	${\displaystyle L_{w,\mathrm {spez} ,n}}$
Size and unit system unit dimension SI dB decibel ${\displaystyle {\mathsf {1}}}$
See also: Sound power level , sound pressure level , fan

The specific sound power level is a characteristic of fans in technical acoustics . It is used to compare fans with regard to their acoustic sound radiation (see sound power ). For this purpose, the dependence of the sound power of the fan on the current operating point on the fan curve is mathematically abstracted according to Madison's relationship.

The specific sound power level results from:

${\displaystyle L_{w,\mathrm {spez} ,n}=L_{w,n}-10\log {\frac {Q}{1\,\mathrm {\tfrac {m^{3}}{s}} }}-20\log {\frac {\Delta p}{1\,\mathrm {Pa} }}}$

Here are

• ${\displaystyle L_{w,\mathrm {spez} ,n}}$ the specific sound power level at the speed ${\displaystyle n}$
• ${\displaystyle L_{w,n}}$the measured sound power level at the volume flow and the pressure increase ${\displaystyle Q}$ ${\displaystyle \Delta p}$

For a further improved comparability, the specific sound power level is given at a speed of . If a measurement is not possible at this speed, it is recommended to convert the specific sound power level measured at a speed using the following method: ${\displaystyle {2900\,\mathrm {min} ^{-1}}}$ ${\displaystyle n}$

${\displaystyle L_{w,\mathrm {spez} ,2900}=L_{w,\mathrm {spez} ,n}-\Delta L_{n}}$

Here are

• ${\displaystyle L_{w,\mathrm {spez} ,2900}}$the specific sound power level for a speed of ${\displaystyle n}$ ${\displaystyle {2900\,\mathrm {min} ^{-1}}}$
• ${\displaystyle \Delta L_{n}}$ the conversion value for a speed of ${\displaystyle {2900\,\mathrm {min} ^{-1}}}$
  • Axial fans: ${\displaystyle \Delta L_{n}=8{,}5\log {\frac {n}{2900}}}$
  • Centrifugal fans: ${\displaystyle \Delta L_{n}=17{,}3\log {\frac {n}{2900}}}$

Figure 1: Specific sound power level as a function of the number of diameters . Fans with good acoustic properties are located in the gray hatched area.

Figure 1 shows the dependency of the specific sound power level on the number of diameters for implemented fans based on Schlender . Fans with good acoustic properties are in the area shown in gray.

swell

1. ↑ H.-U. Banzhaf, T. Carolus, M. Schneider, U. Mauch, C. Kirschinger: Combined aerodynamic and acoustic characteristics map for the selection of axial fans with optimal efficiency and noise . In: VDI reports No. 1922 . March 2006 ( uni-siegen.eu [PDF]).
2. ^ Madison, RD: Fan Engineering (Handbook) 5th ed., Buffalo, New York, Buffalo Forge Company, 1949
3. ↑ Fasold W., Kraak W., Schirmer W .: Taschenbuch Akustik, Part 1, Verlag Technik, Berlin, 1984
4. ^ Schlender F., Klingenberg G .: Fans in action, VDI-Verlag, Düsseldorf, 1996