The discernibility of changes in program band width

TLDR: In this paper, it was shown that changes in band width are detectable about twice as readily with music as with speech, and that one must go from 8 to 15 kc to obtain a change as readily detected as a change from 5 to 8 kc; and that both these changes, for speech, are just sufficient to have an even chance of being detected by listeners having experience in such tests.

Abstract: One of the factors that should be considered in determining how wide a transmission band is required for high fidelity broadcasting is the ability of people to perceive the effects of restricting the band to various limits, when listening to typical radio programs. Tests are described in which this was directly measured. The tests were concerned only with the physical ability to hear the differences in band width and disregarded the question of the enjoyment or aesthetic appreciation of wider bands. It is concluded that changes in band width are detectable about twice as readily with music as with speech; that one must go from 8 to 15 kc. to obtain a change as readily detected as a change from 5 to 8 kc.; and that both these changes, for speech, are just sufficient to have an even chance of being detected by listeners having experience in such tests.