JJF 1446-2014Calibration Specification for Impedance Tubes(Transfer Function Method) (English PDF)

1 Scope (1)

2 References (1)

3 Terminology and units of measurement (1)

4 Overview (2)

5 Metrological characteristics (2)

5.1 spacing error microphones and two microphones and the standard reference sample spacing error (2)

6 Calibration conditions (3)

Environmental conditions 6.1 (3)

7 Calibration items and calibration methods (3)

8 Calibration results expression (7)

9 Recalibration interval (8)

Appendix A calibration certificate-page format (9)

Appendix B absorption coefficient Measurement Uncertainty of Measurement Error of instances (10)

Introduction

This specification based JJF 1071-2010 "National Calibration Specifications writing rules" establishment, the main reference GB/T 18696.2-2002 "acoustic impedance tube sound absorption coefficient and impedance measurement - Part 2. transfer function Number of law "[eqvISO 10534-2.1998 (E)].

This specification is the first release.

Impedance Tube calibration specifications (Transfer Function Method)

1 Scope

This instruction applies to transfer function measurement of sound-absorbing material sound absorption coefficient of resistance tube calibration.

2. References

This specification references the following documents.

JJF 1001-2011 common measurement terms and definitions JJF 1034-2005 acoustic measurement terminology and definitions GB 3102.5-1993 Quantities and units of electricity and magnetism GB 3102.7-1993 Quantities and units of acoustics GB/T 18696.2-2002 acoustic impedance tube sound absorption coefficient and impedance measurement - Part 2. Biography Transfer function method for dated references, only the dated edition applies to this specification; undated reference documents Member, the latest edition (including any amendments) applies to this specification.

3 terminology and units of measurement this specification uses quantities and units GB 3102.5-1993 and GB 3102.7-1993 prescribed.

JJF 1001-2011 and JJF 1034-2005 and as defined in the following terms and definitions apply to this specification.

3.1 The transfer function (H12) transferfunction Acoustic impedance tube is passed to the location of the complex sound pressure ratio of 2 to 1 from the microphone.

According to equation (1) or (2) the calculation.

H12 = p2/p1 (1)

Where.

p1 --- 1 position complex sound pressure;

complex sound pressure p2 --- position 2.

H12 = S12/S11 (2)

Where.

Sound re-S11 --- 1 position since the pressure spectrum;

Sound re-S12 --- position 1 to position 2 pressure of cross spectrum.

3.2 wave number (k0) wavenumber Acoustic angular frequency of the air than sound. Generally complex, according to equation (3) calculation.

k0 = k'0-jk "0 (3)

Where.

k0 --- wave number;

k'0 --- k0 real part of the phase constant;