Lesson 1

1. Lesson 1 • density • The ratio of the mass of a substance to its volume (mass divided by volume)

2. Lesson 2 • pitch • a description of how a sound is perceived as high or low • depends on the frequency of the sound wave

3. Lesson 2 • loudness • perception of the energy of a sound

4. Lesson 2 • intensity • the amount of energy per second carried through a unit area by a wave

5. Lesson 2 • decibel • (dB) • a unit used to compare the loudness of different sounds

6. Lesson 2 • Doppler effect • the change in frequency of a wave as its source moves in relation to an observer

7. Lesson 3 • music • a set of sounds or notes combined in ways that are pleasing

8. Lesson 3 • fundamental tone • the lowest natural frequency of an object

9. Lesson 3 • overtone • a natural frequency that is a multiple of the fundamental tone’s frequency

10. Lesson 4 • ear canal • a narrow region leading from the outside of the human ear to the eardrum

11. Lesson 4 • eardrum • the small, tightly stretched drum like membrane that separates the outer ear from the middle ear, and that vibrates when sound waves strike it

12. Lesson 4 • cochlea • a snail-shaped tube in the inner ear that is lined with receptor cells that respond to sound

13. Lesson 5 • echolocation • the use of reflected sound waves to determine distances or to locate objects

14. Lesson 5 • ultrasound • sound waves with frequencies above 20,000 Hz

15. Lesson 5 • sonar • a system that uses reflected sound waves to locate and determine the distance to objects under water

16. Lesson 5 • sonogram • an image formed using reflected ultrasound waves