The Nature of Tonal Brightness

Abstract

Cardboard Seebeck sirens were arranged so that (a) the ratio of the hole to the interval between the holes (H/I), (b) the linear velocity of the rotating holes (V), and (c) the frequency of the holes (F) could be varied independently. The tonal complexes produced by such stimuli were judged as to their relative brightnesses, and the stimuli were differentiated by the recording of cathode-ray oscillograms and by electrical harmonic analysis obtained from a General Radio Wave Analyzer. Abraham''s theory that tonal brightness is dependent upon H/C was disproved, as due to the artifact of his allowing V to vary with H/C. Brightness varies directly with F. It also varies directly with V because increase in velocity increases the number of higher partials present in the tonal complex. Presumably brightness varies with intensity too, and is to be identified with tonal density as already described (Stevens).