Scivra
Pro 🔒~10 min

Sound Waves

Vibrations, pitch, and volume

How it works

Sound is a mechanical wave caused by vibrations. When an object vibrates (like a guitar string or vocal cords), it pushes and pulls on the surrounding air molecules, creating compressions (dense regions) and rarefactions (sparse regions) that travel outward as a sound wave. Frequency (measured in Hertz, Hz) determines pitch — more vibrations per second = higher pitch. Amplitude determines loudness — bigger vibrations = louder sound. Sound needs matter (air, water, solid) to travel — it cannot travel through a vacuum. Sound travels fastest through solids (about 5000 m/s in steel) and slowest through gases (343 m/s in air).

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Step-by-step

  1. Press Play and adjust the Frequency slider — higher frequency creates higher-pitched sound waves.
  2. Move the Amplitude slider to make the wave bigger (louder) or smaller (quieter).
  3. Switch the medium to Vacuum — the wave disappears!
  4. No matter = no sound.

Key formulas

  • v=fλ(wave speed = frequency × wavelength)v = f\lambda \quad (\text{wave speed = frequency × wavelength})Speed of sound in air ≈ 343 m/s at 20°C
  • fhigh→high pitchAlarge→loudf_{\text{high}} \to \text{high pitch} \quad A_{\text{large}} \to \text{loud}Higher frequency = higher pitch; larger amplitude = louder

Frequently asked questions

What is the pitch of a sound with 440 Hz frequency? What note is this?
440 Hz is a relatively high pitch. It corresponds to the musical note A4 (middle A), used as a tuning reference by orchestras.
Why can't astronauts hear explosions in space?
Sound needs matter (like air molecules) to travel — it creates pressure waves by pushing molecules together. Space is a vacuum with no molecules, so sound cannot propagate.
A sound wave has a frequency of 343 Hz. What is its wavelength in air?
V = fλ → λ = v/f = 343/343 = 1 m. Each full wave cycle is 1 meter long.
Why do you see lightning before you hear thunder, even though they happen at the same time?
Light travels at 3×10⁸ m/s — almost instantaneous. Sound travels at 343 m/s. Over 1 km, light arrives in 0.000003 s; sound takes about 3 seconds. Count seconds between flash and thunder, divide by 3 to estimate km.