Human audio system good at detecting dynamic sound
Variation grabs user attention
Do not use note lengths <0.0825s (not reliably
detected)
Exception: very simple note or two can be as short as 0.03s
Leave a 0.1s gap between serial presentations
for differentiation
High variation in rhythm and pitch is very effective
Patterson(1982) claims different sounds with similar
rhythms can be confused
Rule-of-thumb: keep earcons as short as possible
Two earcons can be recognized simultaneously
Earcons with up to six notes in one second have
been shown to be usable
To give the impression of rhythmic unit: play
first note slightly louder, the last slightly longer