Pneumatic fluid power - Test methods for measuring acoustic emission pressure levels of exhaust silencers
1 Scope
This document specifies two methods of measuring the level of acoustic pressure at the outlet of an exhaust silencer:
- the first method, called "steady-state mode", is intended to evaluate the noise level under steady state flow, i.e. constant upstream pressure (steady-state test according to ISO 6358-1); and
- the second method, called "discharge", is intended to measure the noise level during the decrease of the pneumatic pressure (discharge test according to ISO 6358-2).
This document is applicable to pneumatic exhaust silencers and devices designed to reduce the sound produced by discharges of compressed air, entering in the scope of application of ISO 6358-1 and ISO 6358-2.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 4871:1996 Acoustics- Declaration and verification of noise emission values of machinery and equipment
Note: GB/T 14574-2000 Acoustics - Declaration and verification of noise emission values of machinery and equipment (eqv ISO 4871:1996)
ISO 6358 (all parts) Pneumatic fluid power - Determination of flow-rate characteristics of components using compressible fluids
Note: GB/T 14513 (all parts) Pneumatic fluid power - Determination of flow-rate characteristics of components using compressible fluids [ISO 6358 (all parts) ]
ISO 11202 Acoustics - Noise emitted by machinery and equipment - Determination of emission sound pressure levels at a work station and at other specified positions applying approximate environmental corrections
Note: GB/T 17248.3-2018 Acoustics - Noise emitted by machinery and equipment - Determination of emission sound pressure levels at a work station and at other specified positions applying approximate environmental corrections (ISO 11202 :2010, IDT)
ISO 11654 Acoustics- Sound absorbers for use in buildings - Rating of sound absorption
IEC 60942 Electroacoustics - Sound calibrators
Note: GB/T 15173-2010 Electroacoustics - Sound calibrators (IEC 60942:2003, IDT)
IEC 61260 Electroacoustics - Octave band and fractional-octave band filters
Note: GB/T 3241-2010 Electroacoustics - Octave-band and fractional-octave-band filters (IEC 61260:1995, MOD)
IEC 61672-1 Electroacoustics - Sound level meters - Part 1: Specifications
Note: GB/T 3785.1-2010 Electroacoustics - Sound level meters - Part 1 : Specifications (IEC 61672-1 : 2002, IDT)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 11202 and ISO 6358-1 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
- ISO Online browsing platform: available at https://www.iso.org/obp
- IEC Electropedia: available at http://www.electropedia.org/
3.1
emission sound pressure
p
sound pressure, at a specified position near a noise source, when the source is in operation under specified operating and mounting conditions on a reflecting plane surface, excluding the effects of background noise as well as the effects of reflections other than those from the plane or planes permitted for the purpose of the test
Note: Emission sound pressure is expressed in pascals (pa).
3.2
emission sound pressure level
Lp
ten times the logarithm to the base 10 of the ratio of the square of the emission sound pressure, p, to the square of a reference value, p0
where the reference value, p0, is equal to 20μPa
Note: Emission sound pressure level is expressed in decibels (dB).
3.3
measured equivalent continuous sound pressure level
Lp, T
ten times the logarithm to the base 10 of the ratio of the time average of the square of the emission sound pressure, p, during a stated time interval of duration, T (starting at t₁ and ending at t₂), to the square of a reference value, p0
where the reference value, p0, is equal to 20 μPa.
Note 1: Measured equivalent sound pressure level is expressed in decibels (dB).
Note 2: If specific frequency and time weightings as specified in IEC 61672-1 and/or specific frequency bands are applied, this is indicated by appropriate subscripts, e.g. LAeq denotes the A-weighted emission sound pressure level.
Note 3: The formula in 3.3 is equivalent to that for the environmental noise descriptor “equivalent continuous sound pressure level". However, the emission quantity defined above is used to characterize the noise emitted by a source under test and assumes that standardized measurement and operating conditions as well as a controlled acoustical environment are used for the measurements.
3.4
frequency range of interest
sound levels determined for frequencies from 100 Hz to 20000 Hz
3.5
background noise
noise from all sources other than the source under test
Note: Background noise can include contributions from airborne sound, noise from structure-borne vibration and electrical noise in instrumentation.
3.6
background noise correction
K1A
correction applied to the measured sound pressure levels to account for the influence of background noise
3.7
environmental correction
K2A
term to account for the influence of reflected sound on the mean sound pressure level on the reference measurement surface
Note: Environmental correction is expressed in decibels (dB).
4 Symbols and units
Symbols and units are in accordance with those defined in ISO 6358 and ISO 11202.
5 Test set-up
5.1 Test bench
According to the test method chosen, the test bench shall be in accordance with ISO 6358-1 (steady- state mode) or ISO 6358-2 (discharge mode). In particular, the size of the upstream measurement tube shall be in accordance with ISO 6358-1 specifications.
Relevant for the comparison of the sound emission is the pressure and the flow rate (flow rate is in this case a functional value to ensure that the silencer fits to the application). Therefore, it is recommended to use the test bench from ISO 6358-1 if possible as the measured flow rate is based on a stable pressure. If that in ISO 6358-2 is chosen, the values of pressure and flow change significantly within the test due to the nature of the discharge method. Therefore, the value of the flow rate shows a wider tolerance range
5.2 Pneumatic pressure measurement
Only the pressure in the upstream pressure-measuring tube shall be measured. The set-up shall be in accordance with ISO 6358-1.
5.3 Flow measurement
The flow during the sound pressure measurement shall be recorded. The test set-up shall be in accordance with ISO 6358-1.
Note: Correlative flow characteristic values are also recorded according to ISO 6358-1 or ISO 6358-2.
5.4 Sound pressure measurement
5.4.1 General
The measurement of sound pressure can be done at one or three positions. Measurement at three positions increases the precision of the result and reduces the uncertainty of the measurement. Direct incident flow on microphones should be avoided, due to noise generation by the microphones.
5.4.2 Measurement at one position
In this case, sound pressure shall be measured at one point positioned at 60° from the axis of the measurement tube, at 1m from the centre of the end of the transition connector and at a height of 1 m, as shown in Figure 1.
5.4.3 Measurement at three positions
In this case, sound pressures shall be measured at three positions distributed around the arc of a circle 1m in radius and from the centre of the end of the pressure measurement tube and at a height of 1 m. The points shall be positioned at 15°, 60°and 105° from the axis of the tube, as shown in Figure 2.
Standard
GB/T 43073-2023 Pneumatic fluid power—Test methods for measuring acoustic emission pressure levels of exhaust silencers (English Version)
Standard No.
GB/T 43073-2023
Status
valid
Language
English
File Format
PDF
Word Count
12500 words
Price(USD)
375.0
Implemented on
2023-9-7
Delivery
via email in 1~3 business day
Detail of GB/T 43073-2023
Standard No.
GB/T 43073-2023
English Name
Pneumatic fluid power—Test methods for measuring acoustic emission pressure levels of exhaust silencers
Pneumatic fluid power - Test methods for measuring acoustic emission pressure levels of exhaust silencers
1 Scope
This document specifies two methods of measuring the level of acoustic pressure at the outlet of an exhaust silencer:
- the first method, called "steady-state mode", is intended to evaluate the noise level under steady state flow, i.e. constant upstream pressure (steady-state test according to ISO 6358-1); and
- the second method, called "discharge", is intended to measure the noise level during the decrease of the pneumatic pressure (discharge test according to ISO 6358-2).
This document is applicable to pneumatic exhaust silencers and devices designed to reduce the sound produced by discharges of compressed air, entering in the scope of application of ISO 6358-1 and ISO 6358-2.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 4871:1996 Acoustics- Declaration and verification of noise emission values of machinery and equipment
Note: GB/T 14574-2000 Acoustics - Declaration and verification of noise emission values of machinery and equipment (eqv ISO 4871:1996)
ISO 6358 (all parts) Pneumatic fluid power - Determination of flow-rate characteristics of components using compressible fluids
Note: GB/T 14513 (all parts) Pneumatic fluid power - Determination of flow-rate characteristics of components using compressible fluids [ISO 6358 (all parts) ]
ISO 11202 Acoustics - Noise emitted by machinery and equipment - Determination of emission sound pressure levels at a work station and at other specified positions applying approximate environmental corrections
Note: GB/T 17248.3-2018 Acoustics - Noise emitted by machinery and equipment - Determination of emission sound pressure levels at a work station and at other specified positions applying approximate environmental corrections (ISO 11202 :2010, IDT)
ISO 11654 Acoustics- Sound absorbers for use in buildings - Rating of sound absorption
IEC 60942 Electroacoustics - Sound calibrators
Note: GB/T 15173-2010 Electroacoustics - Sound calibrators (IEC 60942:2003, IDT)
IEC 61260 Electroacoustics - Octave band and fractional-octave band filters
Note: GB/T 3241-2010 Electroacoustics - Octave-band and fractional-octave-band filters (IEC 61260:1995, MOD)
IEC 61672-1 Electroacoustics - Sound level meters - Part 1: Specifications
Note: GB/T 3785.1-2010 Electroacoustics - Sound level meters - Part 1 : Specifications (IEC 61672-1 : 2002, IDT)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 11202 and ISO 6358-1 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
- ISO Online browsing platform: available at https://www.iso.org/obp
- IEC Electropedia: available at http://www.electropedia.org/
3.1
emission sound pressure
p
sound pressure, at a specified position near a noise source, when the source is in operation under specified operating and mounting conditions on a reflecting plane surface, excluding the effects of background noise as well as the effects of reflections other than those from the plane or planes permitted for the purpose of the test
Note: Emission sound pressure is expressed in pascals (pa).
3.2
emission sound pressure level
Lp
ten times the logarithm to the base 10 of the ratio of the square of the emission sound pressure, p, to the square of a reference value, p0
where the reference value, p0, is equal to 20μPa
Note: Emission sound pressure level is expressed in decibels (dB).
3.3
measured equivalent continuous sound pressure level
Lp, T
ten times the logarithm to the base 10 of the ratio of the time average of the square of the emission sound pressure, p, during a stated time interval of duration, T (starting at t₁ and ending at t₂), to the square of a reference value, p0
where the reference value, p0, is equal to 20 μPa.
Note 1: Measured equivalent sound pressure level is expressed in decibels (dB).
Note 2: If specific frequency and time weightings as specified in IEC 61672-1 and/or specific frequency bands are applied, this is indicated by appropriate subscripts, e.g. LAeq denotes the A-weighted emission sound pressure level.
Note 3: The formula in 3.3 is equivalent to that for the environmental noise descriptor “equivalent continuous sound pressure level". However, the emission quantity defined above is used to characterize the noise emitted by a source under test and assumes that standardized measurement and operating conditions as well as a controlled acoustical environment are used for the measurements.
3.4
frequency range of interest
sound levels determined for frequencies from 100 Hz to 20000 Hz
3.5
background noise
noise from all sources other than the source under test
Note: Background noise can include contributions from airborne sound, noise from structure-borne vibration and electrical noise in instrumentation.
3.6
background noise correction
K1A
correction applied to the measured sound pressure levels to account for the influence of background noise
3.7
environmental correction
K2A
term to account for the influence of reflected sound on the mean sound pressure level on the reference measurement surface
Note: Environmental correction is expressed in decibels (dB).
4 Symbols and units
Symbols and units are in accordance with those defined in ISO 6358 and ISO 11202.
5 Test set-up
5.1 Test bench
According to the test method chosen, the test bench shall be in accordance with ISO 6358-1 (steady- state mode) or ISO 6358-2 (discharge mode). In particular, the size of the upstream measurement tube shall be in accordance with ISO 6358-1 specifications.
Relevant for the comparison of the sound emission is the pressure and the flow rate (flow rate is in this case a functional value to ensure that the silencer fits to the application). Therefore, it is recommended to use the test bench from ISO 6358-1 if possible as the measured flow rate is based on a stable pressure. If that in ISO 6358-2 is chosen, the values of pressure and flow change significantly within the test due to the nature of the discharge method. Therefore, the value of the flow rate shows a wider tolerance range
5.2 Pneumatic pressure measurement
Only the pressure in the upstream pressure-measuring tube shall be measured. The set-up shall be in accordance with ISO 6358-1.
5.3 Flow measurement
The flow during the sound pressure measurement shall be recorded. The test set-up shall be in accordance with ISO 6358-1.
Note: Correlative flow characteristic values are also recorded according to ISO 6358-1 or ISO 6358-2.
5.4 Sound pressure measurement
5.4.1 General
The measurement of sound pressure can be done at one or three positions. Measurement at three positions increases the precision of the result and reduces the uncertainty of the measurement. Direct incident flow on microphones should be avoided, due to noise generation by the microphones.
5.4.2 Measurement at one position
In this case, sound pressure shall be measured at one point positioned at 60° from the axis of the measurement tube, at 1m from the centre of the end of the transition connector and at a height of 1 m, as shown in Figure 1.
5.4.3 Measurement at three positions
In this case, sound pressures shall be measured at three positions distributed around the arc of a circle 1m in radius and from the centre of the end of the pressure measurement tube and at a height of 1 m. The points shall be positioned at 15°, 60°and 105° from the axis of the tube, as shown in Figure 2.
