a method of identifying and determining the concentrations of multiple species in a gas sample , includes providing a spectrophone assembly having a detector chamber , supplying the gas sample to the detector chamber and simultaneously passing a plurality of radiations of different wavelengths into the detector chamber to produce multiple acoustic resonances of different frequencies . acoustic resonances in the detector chamber are simultaneously sensed to produce corresponding electrical signals , and the electrical signals are analysed to identify the species present in the gas sample and determine the concentration of each specie .