Sound Slide 2 As an object vibrates it gives off energy to the
particles of matter around it. These vibrations travel through air
in a series of rarefactions and compressions (a longitudinal wave)
Sound is produced as the matter vibrates and travels as a
longitudinal wave A medium is required for sound to be heard. If a
tree falls in the forest and no one is around to hear it, is there
a sound? How vibrations cause sound: Slide 3 The speed depends on
the properties of the medium. Sound can travel through any medium
(solid, liquid or gas). Speed is determined by the temperature,
elasticity and density of the medium through which the sound
travels. Speed of Sound Slide 4 1. 1. Temperature: Sound travels
slower at low temperatures 2. 2. Elasticity (ability to rebound):
The more elastic the medium the faster the sound. Solids are more
elastic than liquids or gases. 3. 3. Density: The more dense the
medium the faster the sound travels, its particles do not move as
fast The fastest sound needs high temperature and a solid medium to
travel through. Properties Slide 5 Pitch: description of sound as
high or low, depends on how fast the particles of the medium
vibrate in a given time (the frequency) so the pitch depends on the
frequency of the waves. High frequency = high pitch Low frequency =
low pitch Doppler Effect: Change in pitch of a moving object as it
comes towards and moves away from you. (NASCAR, Siren) High pitch
as they move toward you and low pitch as they move away from you.
Pitch Slide 6 1 hertz = 1 wave (1 complete rarefaction and
compression) Humans hear from 20 to 20,000 hertz Ultrasonic:
frequencies higher than 20,000 hertz; examples: dogs, cats,
porpoises, bats Infrasonic: Frequencies lower than 20 hertz;
examples: elephants, earthquakes, volcanoes, machinery
Echolocation: use of reflected sound waves to find objects, bats
& dolphins use it! Frequency HIGH PITCH LOW PITCH Slide 7
Loudness is related to the amount of energy carried by a wave **
Amplitude shows loudness** Intensity: determines the loudness of a
sound. Defined as the amount of energy in a certain time, relates
to amplitude Amplitude: the larger the amplitude the greater the
intensity (loudness) Decibel: scale in which intensity is judged. 0
dB = no sound, thunder is 120 dB, sounds with a dB of greater than
120 can cause pain in humans, 85 dB can cause ear damage Loudness
SONIC BOOM Slide 8 Resonance when one object vibrates at the same
natural frequency of a second object it can force that second
object into vibrational motion basically it starts making noise
also. LOOK AT THE VIDEO CLIPS!!! Examples: 1. The ear when you
distinguish different frequencies or tones in the sounds you hear.
2. the shattering of crystal glasses when exposed to a musical tone
of the right pitch (its resonance frequency). Glass Shattering:
https://www.youtube.com/watch?v=rRZT7xO5KN4 Tacoma Narrows Bridge:
https://www.youtube.com/watch?v=3mclp9QmCGs Slide 9 Music: when
sound has a pleasing quality, a definite identifiable pitch and a
repeated timing called rhythm. Noise: any sound that is a random
mix of frequencies or pitches. Examples include chalk on the
chalkboard, jackhammer, baby crying Acoustics the science of sound.
Scientists in this area design perfect concert halls and
auditoriums. Each instrument has its own sound quality or timbre.
Sound quality Slide 10 Sound is used for more than just hearing: 1.
1. Sonar: when sound waves are sent in a straight line down until
it reaches a barrier and is reflected back. Used for fishing, to
find oil, mapping 2. 2. Ultrasonic Cleaning: waves are used to
clean jewelry, electronic components, machine parts. Sound waves
are sent through a liquid where it vibrates causing dirt to be
knocked off the object 3. 3. Ultrasound: sound wave sent through
body and an image is drawn showing body part, can also be used to
treat cancer and is used in physical therapy for injured muscles
Applications of sound
