GB/T 17697-2014Acoustics -- Determination of sound power radiated into a duct by fans -- In-duct method (English PDF)

Foreword

This standard was drafted in accordance with GB/T 1.1-2009 given rules.

This standard replaces GB/T 17697-1999 "Acoustics fan sound power radiated into a duct pipe measuring method." this standard compared with GB/T 17697-1999, the main technical changes are as follows.

--- Expanding the scope of application, including the connecting pipes of the air handler, the connection pipe cleaners, air conditioners and even connecting pipes Then hot air duct;

--- Extend the frequency range of uncertainty;

--- Extend the sampling tube allows maximum mean flow velocity, increasing the flow rate of the sampling tube - modal comprehensive correction value;

--- Increase the technical content of the nose cone and foam balls wind shield;

--- End of the pipe to increase the maximum permissible sound pressure reflection coefficient;

--- Technical terms and in accordance with GB/T 3947-1996 "Acoustic Terminology" is defined.

This standard uses the translation method identical with ISO 5136:2003 "Acoustics fans and other ventilation devices radiated into a duct sound power Determination duct method. " Correspondence between the consistency of the standards of international documents and normative references of the following documents.

--- GB/T 3240-1982 acoustical measurement commonly used frequency (neqISO 266. 1975);

--- GB/T 3241-2010 electro-acoustics octave and fractional octave filters (IEC 61260:1995, MOD).

This standard was proposed by the Chinese Academy of Sciences.

This standard by the National Standardization Technical Committee of Acoustics (SAC/TC17) centralized.

Introduction

Appendix A lists the various parameters to determine flow rate and modal comprehensive correction value. Appendix B provides for two measuring sound with turbulence SNR

Methods. Appendix C shows the ways that one-third octave band sound level to calculate the A-weighted sound power level. Appendix D gives a level and average velocity calculation example modal comprehensive correction value.

Fans and other sound power radiated into a duct ventilation equipment depends in part on the type of pipe acoustic impedance characterization. because this, for a measure to be made clear that the test pipe. The standard test pipe has a circular cross section and muffler end.

Appendix E gives details of typical muffler tip. Since the end of the impedance muffler constructed reality is found in high impedance and low impedance

Between the intermediate value, so these special conditions resulting sound power is the practical application of the representative value. Theoretically, according to the ventilation equipment Impedance data and estimate the actual pipeline application radiated sound power. Because this information is currently not complete, so the calculation of them in acoustics Usually do not consider the impact of impedance.

In order to suppress the turbulent pressure pulsation at the microphone, preferably with a long cylindrical hood (sampling tube). The sampling tube with a microphone Mounted in radial position, so that, even in the plane wave can be calculated based on the high order acoustic modes test sound frequency range determined by the formula Relationship pressure level and sound power level.

If in many different laboratories repeated measurements, the measurement uncertainty according to the expected standard deviation is given (see Chapter 4).

This standard does not detail the provisions measuring conditions (performance measurement) method can refer to the provisions of GB/T 1236 Industrial and conditions.

This standard is one of the ventilation fans and other equipment series of sound power level measurement method.

Usually in the absence of connecting pipes, since the fan inlet and exit plane capable of reflecting sound, fan inlet and outlet into the free-field radiation and radiation into the Sound power conduit is different. This standard specifies the law applicable to the fan duct inlet and outlet sound power radiated into a duct measurement. Fan Jin, Export radiated into free-field sound power should reverberation chamber method (GB/T 6881 series), the free field method (GB/T 3767, GB/T 6882, GB/T 3768) or acoustic intensity method (GB/T 16404 series) was measured.

Fans and other ventilation equipment acoustic radiation into Determination of sound power conduit pipe method

1 Scope