Sound power measurement
Why are sound power measurements taken?
Why are sound power measurements taken?
- A quiet machine is a sign of high quality
- Sound power measurement can be used to determine whether sound insulation is necessary
- The Machinery Directive 2006/42/EC requires the airborne noise emission of the machine at the workplace to be specified. If the sound pressure level of 80 dB(A) is exceeded, the sound power must be specified
- Early detection of damage through noise and vibration measurements
Methods for determining sound power
Methods for determining sound power
Measuring sound pressure
In a sound pressure measurement, the local sound pressure level is recorded at a measurement location including all background noise. This means that you know the sound level at this local point, but not from which direction the sound is coming. This method is therefore well suited for a quiet measuring environment with little background noise.
Measuring sound intensity
In a measurement environment with potential background noise, sound intensity measurement is a good option. For example stationary systems in a production hall. In contrast to the sound pressure measurement, the sound intensity is a vectorial quantity, so that it can be determined from which direction the sound is coming from.
Ambient noise can therefore be better recognized and excluded from the results. The sound power can therefore usually be determined more accurately using sound intensity measurements.
Performance of a sound power measurement
Sound power is usually determined using standardized measurement methods. The following pictogram is a schematic representation of the general process of a sound power measurement.
- Preparation
- Determine microphone positions
- Measurement
- Result evaluation and logging
Step 1: Preparation
In addition to selecting the measurement object, the first step is to select the standard to be used for the measurement. The two series of standards DIN EN ISO 3740 - 3746 and DIN EN ISO 9614 1 - 3 are mainly used for this. The main difference between these two standards is that the 374x series involves sound pressure measurements, whereas the 9614 series involves sound intensity measurements. However, both series of standards have in common that sound pressure or sound intensity measurements are to be carried out at numerous, spatially precisely defined positions. The measurement positions are usually located on an enveloping surface surrounding the measurement object, which can be rectangular, cylindrical or spherical depending on the underlying standard and sound source. The dimensions of the enveloping surface and the measured sound quantities (Pa or W/m²) are then used to determine the total sound power level.
Calculation of LW for a sound pressure measurement (according to DIN EN ISO 3744):
Calculation of LW for a sound intensity measurement (according to DIN EN ISO 9614-1):
Step 2: Determine microphone positions
In practice, however, measuring the standard-compliant measuring positions is very time-consuming and in some cases is even left to the visual judgment of the measuring engineer. This is often helped by self-made constructions or adhesive tape markings on the floor. With the SI Local and the Sound Intensity module of our augmented reality software, however, this is no longer necessary. After entering the dimensions of the measurement object, the AR glasses automatically calculate the enveloping surface and the measurement positions and display them with spatial accuracy. The measurement setup can be seen virtually in the room and remains stationary in place. This allows the measurement engineer to walk around it and carry out the measurement conveniently at all virtual positions.
Step 3: Measurement
Certain criteria must be observed during the measurement. A selection of these criteria is listed below:
- The levels measured at the respective measurement locations must not fluctuate too much
- The background noise must meet certain criteria (e.g. 10dB quieter than the level to be measured)
- The measuring equipment must meet certain quality requirements
Step 4: Result evaluation and logging
Finally, the measurement results are recorded and interpreted. The precise details that are included in a complete logging can be found in the standards mentioned.
Our services
- Determination of the sound power level or the emission sound pressure level of systems, machines, devices and assemblies
- Sound power measurement according to DIN EN ISO 9614 1-3 by means of sound intensity measurement
- Sound power measurement according to DIN EN ISO 3744 / 3746 by means of sound pressure measurement
- Measurement according to the Outdoor Noise Directive (2000/14/EC)
- Measurement of emission values on site
- Determination of sound power level for research purposes
- Individual determination of the sound power level for any kind of plant
- Advice on the correct technical assessment of your products
- Determination of noise emissions for your existing products as well as products in the development phase using comparative measurements