The following links use images or videos to explain tricky concepts in sound. Enjoy!
Sound is a longitudinal wave, which means that it displaces the medium in which it travels in a direction parallel to its propagation. This is in contrast to the way most people intuitively draw waves, which is with the displacement perpendicular to the direction of propagation.
Transverse/Longitudinal Wave Youtube (Slinky):
Transverse/Longitudinal Wave Youtube (Animation):
Visual explanation of constructive vs. destructive interference:
Partially constructive interference:
Complex waveform due to partially constructive interference in a violin:
Explanation of how the “beat” is created:
Example audio samples of different beats:
Video of car horn w/ Doppler Effect:
Wikipedia page w/ animations explaining the Doppler Effect (need to scroll down a little within the “General” section to the bolded word “Proof,” just above the next section, “Analysis,” and click the link that says “Show” if you don’t see animated GIFs.):