Ratio of Frequency Swing to Phase Swing in Phase- and Frequency-Modulation Systems Transmitting Speech

Computed and measured data are presented bearing on the relation between the phase and the frequency swing in phase- and frequency-modulation systems when transmitting speech. The results were found to vary with different voices, with the microphone and circuit characteristics, and with the kind of volume regulation used. With a particular carbon microphone, it was found that a phase deviation of 10 radians corresponds to a frequency deviation of between 11 and 15 kc in a phase-modulation system, and between 6 and 12 kc in a frequency-modulation system, depending on conditions.