Online Guide to Room Acoustics for Musicians

A flickering candle flame in front of a double bass f-hole: The candle flickers due to the interaction between the resonant frequencies of the f-hole and the air vibrations produced by the instrument's sound waves.

Blowing a bottle: When you take a bottle, and blow over the open neck, you hear a sound—that's the resonant frequency of the bottle. If you fill the bottle (or empty it) with a liquid, you will hear the frequency shift: the fuller the bottle (smaller volume), the higher the frequency.

An open car window: The booming sound you hear when opening a car window is a result of the interaction between the airflow around the car and the cabin's resonant frequency.