I'm trying to grasp how pulse waves work. I know that a pulse wave with a duty cycle of 50% is basically a square wave. I read the following on this website:

"Of course, there's nothing stopping us from generating pulse waves with any other duty cycle we please, from 0% (where the wave is permanently rooted to the bottom of the cycle, and is therefore silent) to 100% (where it is rooted to the top of the cycle, and again silent)."

I'm confused. I was initially thinking that sound could be heard from a pulse wave when the wave was rooted to the positive portion of the cycle. What portion of the cycle generates the sound if what they say is true? Help!

2 Answers 2


What makes a signal audible is it's variations, not it's absolute level. Both examples you mention (0% or 100% duty cycles are in fact DC signals, either at 0 or full voltage) can therefore not be audible.

  • That makes sense...I didn't not think of it as a signal...that's very interesting :)
    – 02fentym
    Commented Feb 7, 2015 at 20:44

Sound is generated from signals based on movement of a speaker cone. The cone responds to the voltage applied resulting in a magnetic field that drives a magnet to push the cone. The movement of the cone pushes air which produces pressure waves that we perceive as sound.

At no voltage, the magnet simply sits at rest. At full voltage, the magnet will be pushed to one extreme and stay there. Sound is produced only by movement of the speaker cone, so it is actually the change from one voltage state to another that results in movement of the cone and displacement of air to produce sound.

(Note, there are a few other ways sound can be produced other than a magnetic coil, but all depend on the change of voltage to result in changes of position causing movement of air.)

  • Very interesting. Thanks for the extra info :) up voted!
    – 02fentym
    Commented Feb 7, 2015 at 20:45

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