A thermophone was constructed by forming aluminum thin film on a glass substrate. The sound field in the photoacoustic cell was generated by periodic Joule heating of Al film and the output voltage of the branch microphone inserted in the photoacoustic cell, the electric power injected into the thermophone and thermal properties of the thermophone were measured and compared with Rosencwaig and Gersho theory. The transfer function of the system including the photoacoustic cell and branch microphone was measured in audible frequency range by a comparison method. The results show that this method is useful for quantitative photoacoustic measurements by measuring the a.c. temperature fluctuation on a sample surface.
