Parametric Analysis of the Improved Open Photoacoustic Helmholtz Cell

Abstract

Many photoacoustic cells use a Helmholtz structure for amplification of the photoacoustic signal, but very few of them are open cells. Open Helmholtz cells known from the literature exhibit very poor attenuation of the external acoustic noise, which severely limits their applications. Recent research showed that this problem can be overcome in a so-called improved open photoacoustic Helmholtz cell structure. The paper describes how mechanical dimensions of such a cell affect the frequency response of the cell and its penetration by the external acoustic noise. Properties of the cell were investigated by means of computer simulations based on the loss-improved transmission line model. The analysis showed that appropriate selection of the duct dimensions and buffer volumes should result in over 50 dB attenuation of the external acoustic noise, without noticeably affecting the Q-factor and resonance frequency of the cell.