| A | B |
|---|
| vibration | a quickly repeated back-and-forth motion |
| tuning fork | a Y-shaped metal instrument that vibrates to make musical sounds |
| decibel | a measurement of the loudness of sound |
| amplitude | the width of a sound's pattern |
| pitch | how high or low a sound is |
| frequency | the number of vibrations per second |
| hertz | the unit used for measuring frequency |
| compress | squeeze together |
| expand | get larger |
| sound waves | many compressions and expansions of sound moving through a medium |
| longitudinal wave | a wave that moves back-and-forth |
| medium | a material that carries a wave |
| vacuum | a space where there is no matter; empty space |
| pure sound | a sound that has only one frequency |
| beats | sounds that are heard when two sounds of nearly the same frequency combine |
| natural frequency | the frequency at which an object vibrates best |
| resonant vibration | a vibration cased by another vibration |
| quality | the difference in sounds due to different overtones |
| overtones | the extra frequencies that give a sound its quality |
| echo | a sound that is bounced back by an object |
| sonar | a way of using underwater echoes to find distances |
| notes | musical sounds of different pitches |
| tension | a tightness of a string |
| vocal cords | tissues in the throat that vibrate to make sounds |
| larynx | the part of the throat that holds the vocal cords; the Adam's apple |
| outer ear | the outside part of the ear |
| eardrum | a thin sheet of tissue in the ear that vibrates when sounds hit it |
| ear bones | the three small bones in the middle ear |
| cochlea | the part of the ear that changes vibrations into nerve signals |
| rythm | the beat of music |
| melody | the tune of music |
| chord | three or more notes played together |
| harmony | combining musical notes |
| octave | a set of eight notes of the musical scale |
| percussion instruments | musical instruments played by hitting |
| stringed instruments | musical instruments that make their sound by means of vibrating strings |
| wind instruments | musical instruments played by blowing |
