1. Sound

2. The Nature of Sound
Things vibrate (move back and forth) when they make sound.
Sound travels as a longitudinal wave (series of compressions and rarefactions)
Sound MUST have a medium to vibrate; without a medium there can be no sound (because nothing is vibrating)

3. Speed of Sound Speed of sound depends on 3 factors:
Temperature (kinetic energy of molecules)
Lower temp –slower sound
Higher temp –faster sound

4. Speed of sound
Elasticity (ability to move out of position and then go back)
Lower elasticity-slower sound
Higher elasticity- faster sound
Solids are more elastic-so sound moves faster
Gases are less elastic-so sound moves slower

5. Speed of Sound Density- (compactness)- for materials is the same state
Lower density- faster sound
Higher density- slower sound

6. Intensity and Loudness
Intensity: the amount of energy that flows through a certain area in a specific amount of time
Loudness: human perception of sound intensity (measured on a loudness scale in decibels (dB) human hearing can be damaged by sounds over 120dB.
Increased intensity = increased loudness

7. Frequency and Pitch
Frequency: number of wavelength that pass a point per second (measured in hertz-Hz)
Pitch: how high or low a sound seems to be
Increased frequency = higher pitch
Humans can hear sounds between ,000Hz (subwoofer – 20 to 300 Hz)
Dogs can hear up to 40,000Hz
Bats can hear up to 100,000Hz

8. Ultrasonic Waves Ultrasonic Waves: sounds above 20,000 Hz
Used in medical diagnoses and treatment
Estimate size, shape and depth of underwater objects

9. Infrasonic Waves Infrasonic Waves- sounds below 20 Hz
Even though you can’t “hear” these sounds you may “feel” them as a rumble inside your body

10. Uses of Sound
Sounds provide many everyday uses such as… music, entertainment, sirens, fire alarms, warning signals, bells for timers etc.

11. Acoustics
Acoustics- the study of sound, sometimes there is an echoing effect produced by many reflections of sound. This is called reverberation. Walls of auditoriums, concert halls, etc. should be lined with material that reduce reflection-like carpets and draperies.

12. Echolocation
Echolocation- process of locating objects by emitting sounds and interpreting the sound waves that are reflected back.

13. Sonar
Sonar- a system that uses sound waves to detect objects. (sound waves are sent underwater and the reflected wave is picked up by a microphone)

14. Ultrasound
Ultrasound-used for cleaning and in medicine. Ultrasonic waves can be sent into a person’s body. Reflected ultrasonic waves are used to detect and monitor conditions such as pregnancy, certain types of heart disease, and cancer

15. Doppler Effect
Doppler Effect- the change in pitch or wave frequency when a sound and its receiver move relative to one another
Move closer together- higher frequency and pitch
Move further apart –lower frequency and pitch
Rader guns- use Doppler to measure speed
Weather Doppler- shows movement of winds in storms