The visual representation of sounds in various contexts is reviewed briefly, with particular emphasis on the choice between pictorial and verbal descriptions. Research by the Post Office into the specific problem of depicting the auditory signals (tones) which help customers use the telephone system is described. Application of the population stereotype procedure produced a notation for specifying tones diagrammatically which was superior to the others tested. The aspects of tones studied and the conventions recommended for representing them are: Temporal structure. Time should be plotted on a horizontal axis, the presence of a tone being indicated by a line and its absence by a space.
Pitch, which should be plotted on a vertical axis with the highest notes nearest the top of the diagram.
Loudness, which should be represented by the thickness of a line or bar, with the greater thickness indicating the louder tone.
Timbre, which should be represented by line texture, eg, a wavy line to represent a modulated tone.
Comparison with written descriptions showed that diagrams were more effective aids in simple tone identification tasks, such as those confronting the telephone user, but that people without special training found written descriptions more helpful for complex tasks.