Problem of the instantaneous sound frequency measurement

This paper presents a method for the measurement of the so - called quasi-instantaneous frequency of acoustic signals, which is an approximation of the instantaneous frequency defined on the basis of theoretical considerations. It also describes a measurement system of the (T, f-V) type which was built for this purpose, at the output of which the instantaneous value of the voltage V is proportional to the value of the quasi - period T9 or the quasi - instan¬taneous frequency fa of a signal fed to the input. This system permits conti¬nuous registration of variations of the quasi instantaneous frequency in real time. The characteristics of the system (T, f-V) given here and also the oacil¬lograms of chosen test signals (with prescribed modulating functions) and real signals (e.g. those occurring in rooms) indicate the wide possibilities of its use in practice.