The Effect of Restricted Frequency Characteristics on Intelligibility of Speech in Radio Telephone Channels

Abstract

This paper describes the effect on intelligibility in radio telephone channels when restricted speech frequency characteristics are employed. It is well known that advantages like improvement of intelligibility and reduction of adjacent channel interference are obtained when restricted frequency characteristics are used. The set-up to provide restricted speech characteristics and the procedure adopted to study their effect on intelligibility in radio telephone channels are described. It has been practically verified that a speech frequency band of 1000–2400 c./s. with specific cut-off characteristics provides good intelligibility in the case of radio telephone channels in general and aeronautical radio telephone channels in particular.