What if, installed components were measured for acoustic limits before installation?
- Then we would know their influence on the NVH behavior in advance.
- How can the sound emission of a component be determined?
What is sound power?
Sound power is the sound energy emitted by a component or machine in all directions. It is independent of distance and cannot be measured with a simple sound level meter.
How to calculate the sound power level?
Enveloping surface method of sound pressure levels
- ISO 3745 precision class 1, for anechoic rooms and half-spaces, criterion for measuring environment K2 ≤ 0.5 dB
- ISO 3744 precision class 2, for a free sound field above a reflecting plane, criterion for measurement environment K2 ≤ 4.0 dB
Example of a sound power measurement with 10 microphones and a 10-channel CCP GRAS hemisphere
Determining the sound power with 10 microphones is usually done in the following steps:
- Place the 10 microphones for the sound power measurement so that they are positioned on an imaginary enveloping surface around the test specimen at a specified distance (radius).
- Make sure that the microphones are evenly distributed and capture the sound from different angles to obtain an accurate representation of the total sound power.
- Record the sound data with all 10 microphones simultaneously.
- Calculate the average sound pressure level (Leq) for each microphone during the recording period.
- Calculate an averaged LEQ value based on the LEQ values and add the enveloping surface in dB to the sound power level.
- It is important to use calibrated microphones and follow standardized measurement procedures such as ISO 3744, ISO 3745 to obtain accurate and reliable results.
How does the Sound Power Correlate to the Distance from the Measurement Object?
The Sound power is Independent of Distance:
Regardless of the distance of the sound level meter, the sound power remains the same, it depends only on the sound source
Scientific Fact:
The sound level changes by the distance to the sound source. If the distance to the source is twice as nilwide, the sound level is reduced by 6 dB
The Sum of Sound Level [dB] and Surface [dB] Remain the Same
However, this is cancelled by the integration via the surface
The Result:
When the distance doubles, the sound level decreases by 6 dB, while the surface area increases by 6 dB.
How are the Sound Powers Added up to a Total Sound Power Level?
