How do compound intervals relate to simple intervals?

In music theory, the relationship between simple and compound intervals is defined by their span relative to the octave.

• Simple intervals are defined as any musical interval that encompasses one octave or less.12
• Compound intervals are those larger than an octave.1

Compound intervals are perceived by the ear as expanded variants of their simple counterparts. For example, a tenth is considered a compound interval because it consists of an octave plus a third; consequently, the ear associates it with the simple third interval. By extending the range beyond the octave, compound intervals maintain the harmonic character of the simple interval upon which they are based.1