PROPERTIES OF SOUND CHAPTER 2, SECTION 2

Loudness describes your ___PERCEPTION__ of the energy of a sound. The loudness of sound depends on 2 factors: the amount of _ENERGY_ it takes to make the sound and the __DISTANCE__ from the source of the sound. Energy of a Sound Source The _GREATER_ the energy used to make a sound, the __LOUDER__ the sound. The greater the _AMPLITUDE_ of a wave, the more _ENERGY_ the wave has The larger the _AMPLITUDE_ of the sound wave, The _MORE_ energy it has and the _LOUDER_ the sound.

DISTANCE FROM A SOUND SOURCE _LOUDNESS_ increases the closer you are to a sound source. The closer the sound wave is to its _SOURCE_, the more _ENERGY_ it has in a given area. The amount of energy a sound wave carries per second through a unit area is its _INTENSITY_. A sound wave with _GREATER_ intensity sounds louder. As you move away from a sound source, _LOUDNESS_ decreases because intensity _DECREASES_. Measuring Loudness The unit to measure loudness is called the ___DECIBELS___.

PITCH Pitch The pitch of a sound is a description of how _HIGH_ or _LOW_ the sound seems to a person. The pitch of a sound that you hear depends on the __FREQUENCY_ of the sound wave.

PITCH AND FREQUENCY High frequency = __HIGH_ pitch __LOW__ frequency = low _PITCH__ Sound waves with frequencies above the normal human range of hearing are called __ULTRASOUND__. Sound waves with frequencies below the human range of hearing are called __INFRASOUND__.

CHANGING PITCH Changing Pitch Pitches in music are called _NOTES_. Larynx is another word for _VOICE BOX__. To speak air _VIBRATES__ your vocal cords. Stretched vocal cords produce _HIGHER_ frequency. Relaxed vocal cords produce __LOWER__ pitch

THE DOPPLER EFFECT The Doppler Effect The change in frequency of a wave as its source moves in relation to a observer is called the _DOPPLER EFFECT__. The change in frequency is heard as a change in __PITCH__. What Causes the Doppler Effect When the source moves toward a listener, the _FREQUENCY__ of the wave is _HIGHER_ than it would be if the source were stationary. Sonic Boom __WHEN AN OBJECT FLIES FASTER THAN THE SPEED OF SOUND AND MOVES THROUGH A BARRIER_