The document defines key terms related to sound waves including that sound waves are vibrations that spread from a vibrating object, rareification is where molecules are spread out in a sound wave, and frequency and volume are measured in hertz and decibels respectively. It also discusses echo, echolocation, the Doppler effect, qualities of sound, fundamental frequencies, overtones, resonance, microphones, and sound absorption.

1. SOUND UNIT
VOCABULARY

2. SOUND WAVES
Vibrations that spreads away from a vibrating
object
• Drop a pebble into a pond the waves go away
from where the pebble was dropped

3. RAREFACTION
 Part of a sound wave where molecules are spread out

4. HERTZ
 how frequency is measured (one vibration/second is one hertz Hz)
• Unit of measure

5. VOLUME
 how loud or soft something is (depends on the amount of energy
in the sound wave)

6. DECIBEL
 how volume is measured (dB) F 59 Chart of decibels

7. ECHO
 reflected sound wave (singing in the shower)

8. ECHOLOCATION
 finding things or navigating using sonar (bats, whales, dolphins use
this) Echolocation

9. DOPPLER EFFECT
 change in frequency and pitch as a sound moves towards or away
from you (named for scientist Christian Doppler who discovered it)
 Doppler

10. QUALITY
 what makes a sound different from another sound of same volume
and pitch (2 singers same note, same pitch, one is better)

11. FUNDAMENTAL
 main or basic (fundamental frequency is the lowest frequency
something vibrates, guitar string after it is strummed)

12. OVERTONE
 vibrating at a higher frequency (more times) than the fundamental

13. RESONANCE
 a fullness and richness of sound, build up of vibration (it
“resonates” with you)

14. MICROPHONE-
 an instrument that amplifies sound

15. ABSORPTION
 disappearance of a sound wave into a surface (think of a towel
absorbing) hard surfaces sounds bounce off, soft ones it absorbs