Every object has a natural frequency — the number of times it vibrates per second on its own. When an outside sound matches that frequency closely enough, the vibrations grow. A goblet in this test vibrated at about 800 cycles per second. When the speaker matched within 0.5 Hz, the glass shattered.

Speaker enclosure size shapes the sound you hear at specific frequencies. Different box depths boost or flatten the volume at certain points in the range. You build three sealed plywood enclosures with depths of 500 mm, 400 mm, and 300 mm, then play test tones from 30 Hz to 600 Hz through each one. A decibel meter placed one meter away records whether smaller boxes raise the dB level above the baseline that larger boxes keep flat.

Temperature can shift how many times per second an object vibrates. A 640 Hz tuning fork tested at five temperatures from 0 to 100 degrees Celsius shows a small but steady drop as the fork gets hotter. Heat affects the rate of vibration even in a precisely manufactured instrument.

Precise measurement reveals just how slightly temperature shifts a vibration rate. You cool a 640 Hz tuning fork in a freezer and heat it in stages to test five temperatures: 0°C, 25°C, 50°C, 75°C, and 100°C. At each step you tap the fork and record its frequency with a sound sensor and scope. At 0°C it reads 641.6 Hz. By 100°C it drops to 639.9 Hz — a small but consistent change.

Run a wet finger along the rim of a piece of stemware and the glass vibrates to make a tone. Change the water level and the number of vibrations per second shifts, moving the pitch higher or lower. With less water the pitch shifts one way. With more water it shifts the other. That change in water level is all it takes to control the note.