Dual-cavity structure of the Helmholtz resonator allows for natural
sepaIt should be
also mentioned that dual- or multi-cavity structures allow for easy shaping of the
frequency response and also simplify implementation of differential setups, that
may be used for reduction of acoustic noise as well as for additional increase in
the measured signal (e.g. if the microphones are placed in the cavities in which
the signal phase difference is 180◦
).ration of the sample from the microphone, and prevents from interaction of
the light with the microphone (which would produce a background photoacoustic signal resulting from absorption of the light by the microphone)