4.2.6.3-19 Audio Pattern Codes

If sequences of tones are used to represent information, the patterns should be easily recognizable.

Additional Information:
Warning sounds consisting of "bursts" composed of five or more brief pulses (about 0.1 second in duration) with inter-pulse intervals of .15 to .3 seconds have been recommended. The pulses may be designed to be distinctive with respect to their onset and offset shaping, fundamental frequency, and harmonic structure. The bursts may vary as to the number of pulses, the tempo at which they are presented, and the rhythmic and pitch contours.