Standing wave pipe coupling cavity used for wide-band low-distortion equal-amplitude equal-phase calibration

Abstract

The invention relates to the technical field of acoustic metering and particularly discloses a standing wave pipe coupling cavity used for wide-band low-distortion equal-amplitude equal-phase calibration. The lower end of the standing wave pipe in the standing wave pipe coupling cavity is provided with a loudspeaker, and the loudspeaker is also sealed and fixed by a back end cover; a variable-section reflecting end of which the center is provided with a through hole is sealed and fixed with the upper end of the standing wave pipe, and the coupling cavity with a cylinder structure is sealed and fixed in the center of the upper end of the variable-section reflecting end; moreover, the center of one end of the coupling cavity is provided with a cylindrical groove of which the diameter is the same with the diameter of the circular through hole in the center of the variable-section reflecting end; and a standard microphone and a calibrated microphone are symmetrically installed in the coupling cavity. The design of a variable section is adopted for the coupling cavity, which can provide the effects of stabilizing sound waves with large amplitude and lowering the degree of waveform distortion in the coupling cavity; and meanwhile, the calibration of the sensitivity amplitude and phase of a microphone with high dynamic range, wide frequency range and low distortion degree can be realized by the standing wave pipe coupling cavity, the dynamic range is 94 to 160dB, the frequency range is 500 to 800Hz, the degree of the waveform distortion is smaller than 1 percent, the amplitude consistency bias is smaller than 0.3 percent, and the phase bias is smaller than 0.1 degree.

Description

technical field

[0001] The invention belongs to the technical field of acoustic measurement, and in particular relates to a standing wave tube coupling cavity for broadband low distortion, equal amplitude and equal phase calibration. Background technique

[0002] According to the "JJG175-1998 Testing Condenser Microphone" verification regulations, the verification method of the microphone uses a piston generator as the sound source, and forms a uniform pressure field in the coupling cavity for calibration.

[0003] The main structural forms of the piston generator and the coupling cavity are: a structure in which a DC motor is used to drive the eccentric wheel or a crank to drive the piston. The periodic motion of the piston generates a dynamic pressure field of a single frequency in the coupling cavity. The spatial size of the coupling cavity is required to be smaller than the wavelength 1 / 20 of. The piston generator with this structure has a single frequency, mainly 250Hz...

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