Spectrophonic humidity-trace detection in hydrogen and air

A spectrophone with low resonant frequency compatible with the repetition frequency of a pulsed discharge CO laser is described. The spectrophone is used for humidity detection in hydrogen and air. The simple and inexpensive system provides a detection capacity of 10-100ppb/ {Mathematical expression}. The responsivity of the resonant spectrophone is interpreted taking the dependence of the acoustical quality factor on the geometry into account. © 1978 Springer-Verlag.