“…When the calibrating sound pressure excites the diaphragm, an associating sound pressure will be generated in the back chamber. This sound pressure will also experience pressure leakage and heat conduction effects [27], and the diaphragm deformation of the microphone is then determined by these two sound pressures and its elasticity. Due to the above amplitude attenuation and phase deviation of the generated sound pressures, the microphone voltage output (equivalent to the diaphragm deformation) will not be synchronized with the calibrating sound pressure, and so its phase sensitivity will vary at low frequencies.…”
The low frequency phase characteristics of microphones in a monitoring system are crucial for characterizing large-scale natural and artificial activities—e.g., earthquakes, nuclear explosions, or rocket launchings. At present, microphones are simultaneously calibrated using in-situ or calibrator methods to get their phase consistency. However, the essential primary calibration, which traces their phase sensitivity to basic physical quantities, is grossly overlooked. Recently, we speculated that the microphone phase sensitivity is acoustically controlled by the pressure leakage and heat conduction effects in its back chamber, which will vary at low frequencies. Therefore, by means of the FEA (Finite Element Analysis) technique, simulations of laser pistonphone-based primary microphone calibrations are conducted both in the frequency and time domains. The frequency domain simulation quantifies the phase variation, while the time domain analysis helps us to understand the variation mechanism. It is found that the low frequency phase sensitivity is greatly influenced by its geometries and the venting state and should be pre-calibrated before serving.
“…When the calibrating sound pressure excites the diaphragm, an associating sound pressure will be generated in the back chamber. This sound pressure will also experience pressure leakage and heat conduction effects [27], and the diaphragm deformation of the microphone is then determined by these two sound pressures and its elasticity. Due to the above amplitude attenuation and phase deviation of the generated sound pressures, the microphone voltage output (equivalent to the diaphragm deformation) will not be synchronized with the calibrating sound pressure, and so its phase sensitivity will vary at low frequencies.…”
The low frequency phase characteristics of microphones in a monitoring system are crucial for characterizing large-scale natural and artificial activities—e.g., earthquakes, nuclear explosions, or rocket launchings. At present, microphones are simultaneously calibrated using in-situ or calibrator methods to get their phase consistency. However, the essential primary calibration, which traces their phase sensitivity to basic physical quantities, is grossly overlooked. Recently, we speculated that the microphone phase sensitivity is acoustically controlled by the pressure leakage and heat conduction effects in its back chamber, which will vary at low frequencies. Therefore, by means of the FEA (Finite Element Analysis) technique, simulations of laser pistonphone-based primary microphone calibrations are conducted both in the frequency and time domains. The frequency domain simulation quantifies the phase variation, while the time domain analysis helps us to understand the variation mechanism. It is found that the low frequency phase sensitivity is greatly influenced by its geometries and the venting state and should be pre-calibrated before serving.
“…where P 0 is the static pressure, V pa is the amplitude of volume variation in pistonphone, V p0 is the static volume of pistonphone, κ is the adiabatic index, E pv is the temperature transfer function of pistonphone, 26,27,[31][32][33] ω is the angular frequency, T p is the leakage time constant of pistonphone. 30 Underlined symbols represent complex quantities.…”
Section: Sensitivity Models (In Brief)mentioning
confidence: 99%
“…The lower frequency limit of the laser-pistonphone is 0.01 Hz. The calibrating sound pressure is produced by the sinusoidal vibration of the piston, and is affected by the pressure leakage and heat conduction effects, as given by 27 where P 0 is the static pressure, V pa is the amplitude of volume variation in pistonphone, V p0 is the static volume of pistonphone, κ is the adiabatic index, E pv is the temperature transfer function of pistonphone, 26,27,31–33 ω is the angular frequency, T p is the leakage time constant of pistonphone. 30 Underlined symbols represent complex quantities.Figure 2.Currently designed laser-pistonphone.…”
Section: Phase Sensitivity Of Acoustic Transducersmentioning
confidence: 99%
“…Firstly, sound pressures both in the pistonphone and acoustic transducer will decrease due to the coupled pressure leakage and heat conduction effect. 25,26 Secondly, these sound pressures couple with the diaphragm elasticity, and determine the diaphragm deformation. [27][28][29] Based on these, explicit sensitivity models characterizing the relationship between the diaphragm deformation and structures of acoustic transducer and pistonphone were derived.…”
The phase sensitivity of the condenser type acoustic transducers at low frequencies is crucial for locating large-scale natural and manmade activities, but is now commonly calibrated based on comparison methods. Although the primary method, which traces its sensitivity back to the international standard unit is few studied. Recently, the explicit sensitivity models of the condenser type acoustic transducers based on the laser-pistonphone technique are built, and can be used to study the phase responses of acoustic transducers at infrasonic frequencies. So that, in this paper, the phase sensitivities of acoustic transducers when its rear vent connected to the calibrating sound field or outside atmosphere are studied in detail. Secondly, time domain analysis of generated sound pressures by displacement excitation are derived to reveal the mechanism of phase variation. Calculations show two distinct sensitivities with 90° phase lead and −10° phase lag limits for vent in field and vent out field calibrations, which are dominated by the pressure leakage and heat conduction effects at infrasonic frequencies.
“…1. General view of pistonphone 3202 На таких частотах представляется удобным использовать классический метод пистонфона [4][5][6][7].Во ВНИИФТРИ в 1960-ые гг. был разработан пистонфон 3202, обладающий рабочим диапазоном частот 0,1 -100 Гц (рис.…”
There are presented the results of numerical simulation of an applied acoustic problem – modeling of gas processes occurring in the measuring chamber of the infrasound pistonphone 3202 at different frequencies of piston oscillation (0.1 – 1000 Hz) and characterized by extremely small Mach numbers (9.1·10-7÷9.1·10-3). The simulation was performed using quasi-gas-dynamic (QGD) and quasi-hydrodynamic (QHD) equations of a viscous compressible heat-conducting gas with the use of a time-explicit difference scheme, all spatial derivatives was approximated by central differences. It is shown that QGD and QHD models can be used for a simulation of applied acoustics and, in particular, to the simulation of infrasonic pistonphone: the stability limits of the QGD and QHD algorithms in this problem were determined, the dependence of sound pressure on the tuning parameter α is investigated and it is shown that this dependence is quite small. The spectra of sound pressure at the control point calculated by QGD and QHD are given, their dependence on the tuning parameter α is shown, both models equally predict the value of the sound pressure amplitude at the fundamental frequency oscillations. At the end of the article, the sound pressure at the control point at the fundamental frequency oscillations obtained by using QGD and QHD is compared with the values calculated by using semi-empirical formula of sound pressure at closed volume for a case of small oscillations using the polytropic index obtained by Henry Gerber instead of the adiabatic coefficient.
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