The Resonance Apparatus allows students to investigate the resonant behavior of an enclosed air column when it is stimulated by an external sound source. The air column lengths for multiple resonances at various frequencies can be found and the resulting data can be used to determine the speed of sound. A cylindrical acrylic tube is mounted vertically on a stand base and rod. The tube is open at the top and closed at the bottom by a rubber stopper with a hose barb. A scale is printed along the length of the tube. Flexible tubing connects the bottom of the tube to a large reservoir. The reservoir and tube are partially filled with water, creating an air space in the tube above the water level. The length of the space can be varied by adjusting the height of the reservoir on the support rod. A suitable sound source, which can be a tuning fork (not included) or a tone generator (not included), is held close the the mouth of the tube while the length of the air column is varied. Points of resonance where the sound in the tube becomes louder can be heard and measured. The sound level may also be recorded for later analysis using probeware.