Sound waves simulator

What this simulator shows

Sound is a vibration that travels through the air as a wave. The frequency slider sets how many vibrations happen each second, measured in hertz (Hz), from 100 to 1,000. The amplitude slider sets how big the vibrations are. The top picture is a graph of the air pressure over 1/100 of a second, so 300 Hz shows exactly 3 waves. Below it, a row of air particles bunches up and spreads out as the sound passes. The readout gives the pitch, the closest musical note and the wavelength in air.

• Higher frequency means higher pitch, and the waves are closer together.
• Bigger amplitude means a louder sound, and the waves are taller.
• Doubling the frequency raises the pitch by one octave: 220 Hz to 440 Hz is A3 to A4.
• Sound travels at about 343 meters per second in air, so a 440 Hz wave is about 78 cm long.

Hearing it, safely

Press Play to hear a pure tone from your device. It starts only when you tap, plays quietly, changes as you move the sliders, and stops after 15 seconds or when you press Stop. Keep your device's volume low, especially with headphones. Matching what you see with what you hear is the fastest way to link frequency with pitch and amplitude with loudness.

Common misconceptions

Many children mix up pitch and loudness, calling a high sound "loud" or a low sound "quiet". Changing one slider at a time separates the two. Another common idea is that the wavy line is the shape the sound makes in the air. The line is a graph; in air, sound is a pattern of squashed-together and spread-out particles moving forward, which the particle row shows. Children also often think sound can travel through space. It can't: sound needs particles to pass the vibration along, and space is almost empty.

A 10-minute sound activity

• Set 200 Hz and 50%. Ask the child to describe the wave.
• Move only the frequency to 600 Hz. Ask what changed in the picture and what they predict they will hear.
• Play the sound, at low volume, to check. Then change only the amplitude.
• Try the challenges for a high, quiet sound and a low, loud sound.
• Ask: "What could you do to a guitar string to make a higher note?"

Where this fits in school

• US, grade 1: NGSS 1-PS4-1 asks students to show that vibrating materials make sound and that sound can make materials vibrate.
• US, grade 4: NGSS 4-PS4-1 asks students to model waves in terms of amplitude and wavelength. In middle school, MS-PS4-1 links amplitude to the energy a wave carries.
• England, Year 4: pupils learn that sounds are made by vibrations, find patterns between pitch and the object making it, and between volume and the strength of the vibrations.
• England, Key Stage 3: pupils study frequency in hertz, amplitude and loudness, and the range of frequencies humans and animals can hear.

Learning more

Sound and waves are part of Eurekami's science skill map. Lessons draw and explain wave diagrams step by step, and the AI tutor asks guiding questions when a student mixes up pitch and loudness.