The electromagnet is used in the dynamic speaker. Envelope A graph representing how the amount of energy in a signal changes with time. The portion of an envelope representing how energy is built up is called attack . The portion representing how energy dies out is called decay . The portion representing how energy is sustained is called steady state .
Continuant tones have steady-states.
Violins, clarinets, trumpets, etc. produce this kind of envelope. The envelope of a signal that does not have energy supplied to maintain the vibration. There is no steady-state, only attack and decay. Pianos, woodblocks, xylophones, bells, etc. produce this kind of envelope. Fourier's theorem All complex signals can be reduced to the sum of sine signals with appropriate frequency and amplitude values.