All Sounds Are Produced by the ______Of Material Objects

Sound: ______

•All sounds are produced by the ______of material objects.

•______= The impression about the frequency of a sound.

•______-pitched – high frequency (e.g. ______)

•______-pitched – low frequency ( e.g. ______)

•The average frequency range for normal human hearing is between ______

(for younger people; older people lose the higher frequencies)

•Infrasonic or subsonic = Sounds below ______

•Ultrasonic = frequencies above ______

Sound in Air

•______travel through air or along springs.

•These waves travel with areas of ______and ______

•The ______does not travel from one place to another, but the______does.

Speed of Sound

•The speed of sound in dry air at 0°C is ______

•For each degree above 0°C the speed of sound increases by ______

•Sound travels 15 times faster in steel than air and about ______

•Any matter will transmit sound, whether it is a ______

•Sound cannot travel through a ______.

Intensity

•Intensity is ______

•Sound intensity is objective and measured by instruments such as an ______

•______is a physiological sensation sensed by the brain. It is subjective but related to sound intensity.

•The unit of intensity for sound is the ______(___)

Common Levels of Sound

SOURCE OF SOUND LEVEL (dB)
Jet Engine, at 30 m / 140
Threshold of pain / 120
Loud rock music / ____
Old subway train / 100
Average factory / 90
Busy street traffic / 70
Normal speech / ____
Library / 40
Close Whisper / 20
Normal breathing / 10
Hearing threshold / 0

Forced Vibration

•The vibration of one object causes another object to vibrate.

•Sounding boards are used to increase the ______of a vibrating object (like a string).

Natural Frequency

•Everything vibrates, from planets and stars to atoms and everything in between.

•A ______ is one at which minimum energy is required to produce forced vibrations

•also requires the ______to continue this vibration

Resonance – when the ______of a forced vibration on an object matches the object’s ______, a dramatic ______of the vibrations occurs.

•For example, a swing, or the hollow box parts of musical instruments are designed to work best with resonance.

•In order to resonate, an object must be elastic enough to return to its original position and have enough force applied to keep it moving (vibrating)

Interference

•Sound waves interfere with each other in the same way as all waves.

•______interference - augmentation

•______interference - cancellation

The Doppler Effect: Waves from a Moving Source

•v=f λ so a ______

•Motion of either the source or the observer of a wave causes ______

•If the relative motion results in more wave crests reaching the observer per second, the frequency ______

•If the relative motion results in fewer wave crests reaching the observer per second, the frequency ______

Standing Waves

•Although waves usually travel, it is possible to make a wave stay in one place. A wave that is trapped in one spot is called a ______.

•Standing waves are the result of ______. The resultant wave is created by the interference of two waves traveling at the same frequency, amplitude and wavelength but in ______.

•In a standing wave, the ______remain stationary. This is where you can touch a standing wave on a rope without disturbing the wave.

•The positions on a standing wave with the largest amplitudes are known as ______. They occur halfway between nodes.

•Standing waves can be set up on the ______, in organ pipes, and by blowing across the top of a soda bottle.

•Only certain frequencies of vibration produce standing waves for a given string length.

•The wavelength of each of the standing waves depends on ______

•λn = ______