ABOUT PAL

 

 Sound Power Level Measurement Service

 
 
What is sound power?
 
Sound Power is defined as the energy emitted by a sound source per time with unit Watt (W). It usually uses 10-12 Watt (W0) to be the reference power and expresses logarithmically in dB or Bell (10dB), as shown in below:
 
 
Where LW is the sound power level
 
For a stationary sound source, its sound power is a fix value and independent with the measurement position. Oppositely, sound pressure is directly dependent on the measurement position. Therefore, when declaring sound pressure level, the measurement position also shall be declared clearly, otherwise the measurement would be meaningless. On the other hand, when declaring sound power level, measurement position is not necessary to report.
Analog sound power/pressure to an air conditioner can give you a simple comprehension. Sound power could be analogized to the BTU of an air conditioner. It is a fix value, independent with the position. Sound pressure could be analogized to the measured temperature at a certain distance of the air conditioner.
 
 
Extracted from http://www.sengpielaudio.com/SoundPressureAndSoundPower.pdf
 
 
How to choose to measure sound power or sound pressure?
 
General speaking, if you want to know the noise level that a user really perceived, measuring the sound pressure level is preferred. For example, when a person uses a laptop, the operation position is almost fixed. PAL recommends following ISO7779 operator position to measure the sound pressure level. On the other hand, if you want to know to the noise specifications among different products. PAL recommends measuring the sound power level directly. Because the sound power levels are fixed values, it is more straightforward than the sound pressure. There are more and more international labels adopt sound power level to be their noise criteria, such as Blue Angel (Germany), Nordic Swan (Nordic area), Energy Star (USA), EU-flower (EU), TCO, GS Mark, and Green Mark (Taiwan)…etc.
 
    
 
 
How to measure and declare sound power level?
 
PAL follows the below ISO standards to perform sound power level test:
● ISO7779: Acoustics - Measurement of airborne noise emitted by information technology
                  and telecommunication equipment
● ISO3744: Acoustics-Determination of sound power levels of noise sources using sound
                  pressure-Engineering method in an essentially free field over a reflecting plane
● ISO6926: Requirements for the performance and calibration of reference sound sources
                  used for the determination of sound power levels
 
Besides, PAL follows the below ISO standards to declare the sound power:
   ● ISO9296: Acoustics - Declared noise emission values of computer and business equipment
   ● ISO9295: Measurement of high frequency noise emitted by computer and business
                       equipment
 
When measuring, the equipment under test (EUT) will be placed inside a hemi-sphere
or parallelepiped surface depending on the size or characteristic of the sound source,
as shown in below picture:
 
 
 
 
Contact with PAL
 
If you need more info, please contact with PAL’s sales representative directly.
      
     E-mail: sales@pal-acoustics.com
     Tel: 886-2-26272515