Click image to open full size
Music
Instrument Families
How Each Group Makes Sound
Related Tools
Related Labs
Related Worksheets
Musical instruments make sound by creating vibrations that travel through the air as sound waves. Each instrument family starts those vibrations in a different way, such as plucking a string, buzzing lips, striking a surface, or blowing air across an opening. Understanding how instruments make sound helps students connect music to physics concepts like frequency, amplitude, resonance, and wave speed. It also explains why a violin, trumpet, flute, and drum can play the same note but still sound different.
Key Facts
- Sound is produced by vibration: a moving string, air column, membrane, or solid body pushes and pulls on nearby air.
- Frequency controls pitch: higher frequency means higher pitch, and lower frequency means lower pitch.
- Wave speed equation: v = fλ, where v is wave speed, f is frequency, and λ is wavelength.
- String instruments often change pitch using string length, tension, and mass per length: shorter, tighter, lighter strings vibrate faster.
- Wind and brass instruments often change pitch by changing the effective length of a vibrating air column.
- Loudness depends mainly on amplitude: larger vibrations usually produce louder sounds.
Vocabulary
- Vibration
- A repeated back and forth motion that creates sound when it disturbs the surrounding air.
- Resonance
- A strong vibration that happens when an object or air column is driven at one of its natural frequencies.
- Pitch
- How high or low a sound seems, mainly determined by the frequency of vibration.
- Timbre
- The tone color or quality that lets listeners tell different instruments apart even when they play the same pitch.
- Air column
- The vibrating body of air inside a wind or brass instrument that helps determine the pitch.
Common Mistakes to Avoid
- Thinking louder means higher pitch is wrong because loudness depends on amplitude, while pitch depends on frequency.
- Saying brass instruments make sound only because metal vibrates is wrong because the sound begins mainly with buzzing lips that set the air column vibrating.
- Assuming all woodwinds use wooden reeds is wrong because flutes are woodwinds but make sound when air is blown across an opening.
- Ignoring resonance is wrong because the body of a guitar, the tube of a trumpet, or the shell of a drum strengthens and shapes the sound.
Practice Questions
- 1 A guitar string vibrates at 220 Hz. If the sound wave travels through air at 340 m/s, what is its wavelength?
- 2 A flute note has a wavelength of 0.68 m in air where sound travels at 340 m/s. What is the frequency of the note?
- 3 A violin and a clarinet play the same note at the same loudness, but they still sound different. Explain which sound property is different and what physical features of the instruments cause it.