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.
What is it called when something is repeatedly pushed in one direction, then returns?
Vibration (also called oscillation). Any repeating back-and-forth motion is vibration. Sound starts when something vibrates.
Sound Lab
Experiment with amplitude, frequency, wavelength, and period. Each property shapes the wave in a different way.
Sound Lab
Tap to start
Amplitude = volume. Drag up and down to change it.
Key Terms
Click each card to flip it and see the definition.
Amplitude
tap to flip
Amplitude
The height of the wave from the center line to its peak. Amplitude determines how loud a sound is — taller waves carry more energy and produce louder sound.
Frequency
tap to flip
Frequency
How many times the wave repeats per second, measured in Hertz (Hz). From Latin frequentia — how frequently the wave cycles. Higher frequency = higher pitch.
Wavelength
tap to flip
Wavelength
The distance from one wave peak to the next — how long one complete cycle is in space. Wavelength and frequency are inversely related: when one goes up, the other goes down.
Period
tap to flip
Period
How long it takes for one complete cycle to occur, measured in time. Period is the reciprocal of frequency: if frequency is high, each cycle must be short (small period).
How these apply in ultrasound → future lesson. For now, the key idea: these four properties describe every wave.
Quick Check
Amplitude controls which quality of sound?
Concept Recall
When you increase frequency, the wave cycles become:
Hint: it's called frequency because of how frequently...