In sound design, I think the Doppler effect is important. The Doppler effect is a phenomenon where the frequency of a wave received by an observer is not the same as the frequency emitted by the source when there is relative motion between the source and the observer. A train whistle coming from a distance becomes sharp (i.e. higher in frequency and shorter in wavelength) and a train whistle leaving us becomes low (i.e. lower in frequency and longer in wavelength), which is a phenomenon of the Doppler effect.

The cocktail party effect is a human auditory selectivity in which attention is focused on a particular person’s conversation while ignoring other conversations or noises in the background. The effect reveals a surprising ability in the human auditory system that allows us to talk in the midst of noise.