Sound power measurement

Fundamentals of sound power measurement: Lp 100 dB vs. Lw 100 dB

The sound pressure level Lp describes an air pressure fluctuation in the unit dB (decibel). The decibel value is the logarithmic ratio of the existing air pressure fluctuation in Pa (in Pascal) to the reference air pressure of 20 μPa (20 μPa = 0.00002 Pa [Pascal Pa= N/m²]). The 20 μPa represent the lowest hearing threshold of the human auditory system, which is why they are referenced here.

Formel Schalldruckpegel - Schalleistungsmessung I Formula sound pressure level - sound power measurement

  • The sound pressure level represents a local air pressure fluctuation, whose magnitude is characterized by dB.
  • It depends on the measuring/emission location of the sound power measurement.
  • Lp 100 dB corresponds to an air pressure fluctuation of 2 Pa

The sound power level Lw, on the other hand, describes the sound energy continuously emitted by the sound source [measurement object] per second. Therefore it has the unit Watt (W). However, the sound power level Lw in decibels (dB) is more common. The determination is similar to the calculation of the sound pressure level. However, the existing sound power PAK (in Watt) must first be brought into a logarithmic ratio with the reference value P0, which is standardized for airborne sound, with 10 -12 Watt.

Formel Schallleistungspegel - Schallleistungsmessung I Formula sound power level - sound power measurement

  • The sound power level characterizes the entire sound source and is therefore not dependent on the location (Theoretically: it can be used to calculate the sound pressure level at any location)
  • It is not directly measurable, but is determined using standardized procedures.
  • Lw 100 dB corresponds to an output power of 0.01 W.

Note: Sound power level is not equal to sound pressure level

LW 100 dB  vs.   LP 100 dB    ->    Lw  0,01 W      LP  2 Pa

Due to the very similar calculation and the dimensionless unit dB, confusion occasionally occurs in professional circles.

Note: The corresponding indices are of enormous importance.

Performance of a sound power measurement

The determination of the sound power is usually carried out according to standardized measuring methods. In the following pictogram the general procedure of a sound power measurement is shown schematically.

konventioneller Ablauf einer Schallleistungsmessung I Conventional procedure of a sound power measurement

  1. Preparation
  2. Determine microphone positions
  3. Measure
  4. Report

To step 1 Preparation

Besides the selection of the object to be measured, the first step is the selection of the standard to be used for the measurement. For this purpose, the two standards DIN EN ISO 3740 – 3746 and DIN EN ISO 9614 1 – 3 are mainly used. The main difference between these two standards is that the 374x series is used for sound pressure measurements whereas the 9614 series is used for sound intensity measurements. However, both series of standards have in common that sound pressure or sound intensity measurements have to be carried out at numerous, spatially precisely defined positions. The measuring positions are usually located on an enveloping surface surrounding the measured object, which can be cuboid, cylindrical or spherical, depending on the underlying standard and the sound source. Finally, the dimensions of the enveloping surface and the measured sound quantities (Pa or W/m²) are used to determine the total sound power level.

Calculation LW for sound pressure measurement (according to DIN EN ISO 3744):

Formel zur Schalldruckbestimmung nach DIN EN ISO 3744 - Schallleistungsmessung I Formula for sound pressure determination according to DIN EN ISO 3744 - Sound power measurement

Parameter der Schalldruckbestimmung - Schallleistungsmessung I Parameters of sound pressure determination - sound power measurement

Calculation LW for sound intensity measurements (according to DIN EN ISO 9614-1):

Formel zur Schallintensitätsbestimmung DIN EN ISO 9614-1 - Schallleistungsmessung I Formula for determining sound intensity DIN EN ISO 9614-1 - Sound power measurement Parameter der Schallintensitätsbestimmung - Schallleistungsmessung I Parameters of sound intensity determination - sound power measurement

To step 2: Determine microphone positions:

After the measurement procedure has been defined, the microphone positions around the real measurement object have to be sounded out. Depending on the size of the test object, this can be very complex and time-consuming in practice. A simplification is provided by the use of state-of-the-art AR (Augmented Reality) technology. For this reason, we have developed a software which allows to determine the standard microphone positions with centimeter accuracy using AR glasses. Further information will follow shortly.

To step 3. measurement:

During the measurement certain criteria have to be met. In the following a selection of these criteria is listed in brief:

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

To 4. Logging:

Last but not least the logging and interpretation of the measurement results is done. The exact details that belong in a complete protocol can be found in the standards mentioned above.

Our services include

  • Determination of the sound power according to DIN EN ISO 9614 1-3 by means of sound intensity measurement
  • Sound power according to DIN EN ISO 3744 / 3746
  • Measurement according to the Outdoor Noise Directive (2000/14/EG)
  • Determination of sound power levels for research purposes
  • Individual determination of the sound power level for your plant

Copyright 2021 – HoloMetrix GmbH 

Sound power measurement

Fundamentals of sound power measurement: Lp 100 dB vs. Lw 100 dB

The sound pressure level Lp describes an air pressure fluctuation in the unit dB (decibel). The decibel value is the logarithmic ratio of the existing air pressure fluctuation in Pa (in Pascal) to the reference air pressure of 20 μPa (20 μPa = 0.00002 Pa [Pascal Pa= N/m²]). The 20 μPa represent the lowest hearing threshold of the human auditory system, which is why they are referenced here.

Formel Schalldruckpegel - Schalleistungsmessung I Formula sound pressure level - sound power measurement

  • The sound pressure level represents a local air pressure fluctuation, whose magnitude is characterized by dB.
  • It depends on the measuring/emission location of the sound power measurement.
  • Lp 100 dB corresponds to an air pressure fluctuation of 2 Pa

The sound power level Lw, on the other hand, describes the sound energy continuously emitted by the sound source [measurement object] per second. Therefore it has the unit Watt (W). However, the sound power level Lw in decibels (dB) is more common. The determination is similar to the calculation of the sound pressure level. However, the existing sound power PAK (in Watt) must first be brought into a logarithmic ratio with the reference value P0, which is standardized for airborne sound, with 10 -12 Watt.

Formel Schallleistungspegel - Schallleistungsmessung I Formula sound power level - sound power measurement

  • The sound power level characterizes the entire sound source and is therefore not dependent on the location (Theoretically: it can be used to calculate the sound pressure level at any location)
  • It is not directly measurable, but is determined using standardized procedures.
  • Lw 100 dB corresponds to an output power of 0.01 W.

Note: Sound power level is not equal to sound pressure level

LW 100 dB  vs.   LP 100 dB    ->    Lw  0,01 W      LP  2 Pa

Due to the very similar calculation and the dimensionless unit dB, confusion occasionally occurs in professional circles.

Note: The corresponding indices are of enormous importance.

Performance of a sound power measurement

The determination of the sound power is usually carried out according to standardized measuring methods. In the following pictogram the general procedure of a sound power measurement is shown schematically.

konventioneller Ablauf einer Schallleistungsmessung I Conventional procedure of a sound power measurement

  1. Preparation
  2. Determine microphone positions
  3. Measure
  4. Report

To step 1 Preparation

Besides the selection of the object to be measured, the first step is the selection of the standard to be used for the measurement. For this purpose, the two standards DIN EN ISO 3740 – 3746 and DIN EN ISO 9614 1 – 3 are mainly used. The main difference between these two standards is that the 374x series is used for sound pressure measurements whereas the 9614 series is used for sound intensity measurements. However, both series of standards have in common that sound pressure or sound intensity measurements have to be carried out at numerous, spatially precisely defined positions. The measuring positions are usually located on an enveloping surface surrounding the measured object, which can be cuboid, cylindrical or spherical, depending on the underlying standard and the sound source. Finally, the dimensions of the enveloping surface and the measured sound quantities (Pa or W/m²) are used to determine the total sound power level.

Calculation LW for sound pressure measurement (according to DIN EN ISO 3744):

Formel zur Schalldruckbestimmung nach DIN EN ISO 3744 - Schallleistungsmessung I Formula for sound pressure determination according to DIN EN ISO 3744 - Sound power measurement

Parameter der Schalldruckbestimmung - Schallleistungsmessung I Parameters of sound pressure determination - sound power measurement

Calculation LW for sound intensity measurements (according to DIN EN ISO 9614-1):

Formel zur Schallintensitätsbestimmung DIN EN ISO 9614-1 - Schallleistungsmessung I Formula for determining sound intensity DIN EN ISO 9614-1 - Sound power measurement Parameter der Schallintensitätsbestimmung - Schallleistungsmessung I Parameters of sound intensity determination - sound power measurement

To step 2: Determine microphone positions:

After the measurement procedure has been defined, the microphone positions around the real measurement object have to be sounded out. Depending on the size of the test object, this can be very complex and time-consuming in practice. A simplification is provided by the use of state-of-the-art AR (Augmented Reality) technology. For this reason, we have developed a software which allows to determine the standard microphone positions with centimeter accuracy using AR glasses. Further information will follow shortly.

To step 3. measurement:

During the measurement certain criteria have to be met. In the following a selection of these criteria is listed in brief:

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

To 4. Logging:

Last but not least the logging and interpretation of the measurement results is done. The exact details that belong in a complete protocol can be found in the standards mentioned above.

OUR SERVICES INCLUDE

  • Determination of the sound power according to DIN EN ISO 9614 1-3 by means of sound intensity measurement
  • Sound power according to DIN EN ISO 3744 / 3746
  • Measurement according to the Outdoor Noise Directive (2000/14/EG)
  • Determination of sound power levels for research purposes
  • Individual determination of the sound power level for your plant

Copyright 2021 – HoloMetrix GmbH 

Sound power measurement

Fundamentals of sound power measurement: Lp 100 dB vs. Lw 100 dB

The sound pressure level Lp describes an air pressure fluctuation in the unit dB (decibel). The decibel value is the logarithmic ratio of the existing air pressure fluctuation in Pa (in Pascal) to the reference air pressure of 20 μPa (20 μPa = 0.00002 Pa [Pascal Pa= N/m²]). The 20 μPa represent the lowest hearing threshold of the human auditory system, which is why they are referenced here.

Formel Schalldruckpegel - Schalleistungsmessung I Formula sound pressure level - sound power measurement

  • The sound pressure level represents a local air pressure fluctuation, whose magnitude is characterized by dB.
  • It depends on the measuring/emission location of the sound power measurement.
  • Lp 100 dB corresponds to an air pressure fluctuation of 2 Pa

The sound power level Lw, on the other hand, describes the sound energy continuously emitted by the sound source [measurement object] per second. Therefore it has the unit Watt (W). However, the sound power level Lw in decibels (dB) is more common. The determination is similar to the calculation of the sound pressure level. However, the existing sound power PAK (in Watt) must first be brought into a logarithmic ratio with the reference value P0, which is standardized for airborne sound, with 10 -12 Watt.

Formel Schallleistungspegel - Schallleistungsmessung

  • The sound power level characterizes the entire sound source and is therefore not dependent on the location (Theoretically: it can be used to calculate the sound pressure level at any location)
  • It is not directly measurable, but is determined using standardized procedures.
  • Lw 100 dB corresponds to an output power of 0.01 W.

Note: Sound power level is not equal to sound pressure level

LW 100 dB  vs.   LP 100 dB    ->    Lw  0,01 W      LP  2 Pa

Due to the very similar calculation and the dimensionless unit dB, confusion occasionally occurs in professional circles.

Note: The corresponding indices are of enormous importance.

Performance of a sound power measurement

The determination of the sound power is usually carried out according to standardized measuring methods. In the following pictogram the general procedure of a sound power measurement is shown schematically.
  1. Preparation
  2. Determine microphone positions
  3. Measure
  4. Report

To step 1 Preparation

Besides the selection of the object to be measured, the first step is the selection of the standard to be used for the measurement. For this purpose, the two standards DIN EN ISO 3740 – 3746 and DIN EN ISO 9614 1 – 3 are mainly used. The main difference between these two standards is that the 374x series is used for sound pressure measurements whereas the 9614 series is used for sound intensity measurements. However, both series of standards have in common that sound pressure or sound intensity measurements have to be carried out at numerous, spatially precisely defined positions. The measuring positions are usually located on an enveloping surface surrounding the measured object, which can be cuboid, cylindrical or spherical, depending on the underlying standard and the sound source. Finally, the dimensions of the enveloping surface and the measured sound quantities (Pa or W/m²) are used to determine the total sound power level. Calculation LW for sound pressure measurement (according to DIN EN ISO 3744): Calculation LW for sound intensity measurements (according to DIN EN ISO 9614-1):

To step 2: Determine microphone positions:

After the measurement procedure has been defined, the microphone positions around the real measurement object have to be sounded out. Depending on the size of the test object, this can be very complex and time-consuming in practice. A simplification is provided by the use of state-of-the-art AR (Augmented Reality) technology. For this reason, we have developed a software which allows to determine the standard microphone positions with centimeter accuracy using AR glasses. Further information will follow shortly.

To step 3. measurement:

During the measurement certain criteria have to be met. In the following a selection of these criteria is listed in brief: 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

To 4. Logging:

Last but not least the logging and interpretation of the measurement results is done. The exact details that belong in a complete protocol can be found in the standards mentioned above.

OUR SERVICES INCLUDE

  • Determination of the sound power according to DIN EN ISO 9614 1-3 by means of sound intensity measurement
  • Sound power according to DIN EN ISO 3744 / 3746
  • Measurement according to the Outdoor Noise Directive (2000/14/EG)
  • Determination of sound power levels for research purposes
  • Individual determination of the sound power level for your plant

Copyright 2021 – HoloMetrix GmbH