Sound is vibration — a back-and-forth movement. Imagine plucking a guitar string: it blurs because it's moving rapidly in both directions. That motion is vibration. When something vibrates, it pushes the medium — the material around it. For everyday sound, the medium is air, but sound also travels through water, metal, and tissue around it in waves — disturbances that spread outward, like ripples when you drop a stone in water.
Those waves carry energy — the ability to make something happen. A sound wave's energy is what moves your eardrum, which is how you hear to your ears, and your brain interprets them as sound.
Two things change how a sound wave looks and sounds: :how tall the wave is, and :how fast it repeats.
Vibration (also called oscillation). Any repeating back-and-forth motion is vibration. Sound starts when something vibrates.
Experiment with amplitude, frequency, wavelength, and period. Each property shapes the wave in a different way.
Click each card to flip it and see the definition.
How these apply in ultrasound → future lesson. For now, the key idea: these four properties describe every wave.
Amplitude is the height of the wave — how far it reaches from the center line.
Think of ocean waves: a calm day has small waves (low amplitude), a storm has towering waves (high amplitude). In sound, more amplitude = louder volume.
You will control amplitude in the Sound Lab on the next tab.
Frequency is how many times the wave repeats per second — how frequently it cycles.
A whistle has high frequency (many cycles per second, high pitch). Thunder has low frequency (few cycles per second, low pitch).
We measure it in Hertz (Hz). 440 Hz means 440 complete cycles every second — that is the note A above middle C.