Abstract
It is shown experimentally that a microplasma created by a microstructured electrode array is sensitive to sound pressure. In this paper, two electrode architectures are used to create the microplasma. The sensitivity of these microplasma microphones, close to 0.4 nA/Pa, is estimated using a waveguide and a calibration method by comparison with a reference microphone. An empirical expression of the acoustic pressure sensitivity of microdischarges is proposed. The predictions of this empirical model are in good agreement with the experimental data.
Highlights
An ionized gas or plasma is a mixture of electrons, ions and neutrals
An acoustic wave passing through the plasma volume of a discharge provokes fluctuations in its electrical current which is the principle of acoustic sensors
After 2 kHz, Figure 9 shows a significant discrepancy between the frequency responses of the microplasma microphone and the reference microphone
Summary
An ionized gas or plasma is a mixture of electrons, ions and neutrals. In air, at atmospheric pressure, the plasma is generated by applying a DC voltage between two electrodes. The content of this paper completes the experimental work of the same authors on microphonic devices using a plasma as sensing element [16] In these plasma microphones (Fig. 1), the ionized gas is generated using negative point-to-plane discharges where a DC high negative voltage is applied to the needle electrode placed above a ground plane, metallic electrodes being separated by a millimetric or a sub-millimetric air gap (three-dimensional setup). The electrode gap dimensions in the micrometer range are small enough to generate sufficiently high electric field strengths to ignite discharges by applying only moderate voltages (’500 V) In order to stabilize microdischarges, each electrode with points is connected to a ballast resistance (R ’ 23 MX)
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