Abstract :
In Part 1, possible methods of calibrating a Rayleigh disc are discussed, and details are given of a comparison between two of these, namely, by means of low-frequency alternating air currents and by calculation based on the theoretical formula. In consequence of agreement found between these, the latter has been adopted as the most convenient practical method of calibration. In Part 2, comparisons are made between Rayleigh discs of different sizes and compositions, both in spherical sound waves and in a closed resonating tube. The influence of internal resonances of mica discs on velocity measurement is investigated. In Part 3, comment is made on practical considerations affecting acoustic measurements by means of a Rayleigh disc.
