The Physics Of Sound Why do we hear what we hear? (Turn on your
speakers)
Slide 3
How are sound waves produced? Mechanical waves Sound energy
requires matter in order to transport it Sound Energy (pulses)
create vibrations causing changes in pressure
Slide 4
How are sound waves produced?produced A longitudinal wave
caused by pressure fluctuations in vibrating objects: Compressions:
high pressure regions (crowded area) Rarefactions: low pressure
regions (relaxed area) Frequency- # of compressions passing/second
Wavelength distance between compressions A 3-dimensional
arrangement
Slide 5
What happens to the speed of sound in different types of matter
(media)? Each substance transfers sound energy at a different rate
The rate is dependent on: Tension - the higher the tension between
molecules, the faster sound travels though a medium. thermal energy
- higher the temperature, the faster the molecules move and allow
sound to travel through medium.
Slide 6
How do you break the sound barrier? Supersonic - an object
moves faster than the speed of soundSupersonic Moving at the speed
of sound is known as Mach 1 Exceeding Mach 1 (the sound barrier)
causes a shock wave known as a sonic boom Used to determine the
speed of an aircraft What is meant by Mach 2, or 3 etc. ?
Slide 7
What is a sound detector? Converts sound energy into other
forms of energy. Allows humans to observe a sound wave Often
converts a compression (longitudinal wave) into a electromagnetic
wave (transverse wave) Ex. Microphone, the ear, ultrasonic
machine
Slide 8
Slide 9
How does the ear work as a sound detector? collects and directs
sound vibrates and send to the middle ear Lever system that
amplifies sound vibrations Vibration of tiny hairs, transmitted to
brain by nerves
Slide 10
The three components of sound are: Pitch (how high or low)
Loudness (volume) Timbre (tone color)
Slide 11
What is the relationship between the frequency and pitch of a
sound? Pitch is the highness or lowness of a sound perceived by
humans The qualitative observation (how high or low) derived from
the frequency Frequency is the measurable quantity The quantitative
observation Measured in Hertz The higher the frequency, the higher
the pitch
Slide 12
When the frequency of a sound doubles we say that the pitch
goes up an octave. We can hear a range of pitches of about ten
octaves. Many animals can make sounds and hear frequencies that are
beyond what we can hear.
Slide 13
What frequencies can humans hear? Human Range (audible) 20 Hz -
20,000 Hz We hear best between 200 and 2000 Hz Changes with age and
damage to the ear Ultrasonic Anything above 20,000 Hz Used for
sonar and medical diagnosis Infrasonic Anything below 20 Hz Heavy
machinery, lightning, elephants We might not hear it, but you may
feel these
What is the relationship between the amplitude and loudness of
a sound? Loudness is the volume a sound perceived by humans A
qualitative measure of the power in a wave Can be quantified using
decibels derived from the amplitude Amplitude is the measurable
quantity The quantitative observation Measured in meters The larger
the amplitude, the more energy in a wave and the more powerful it
is.
Slide 17
Loudness vs. Decibel Source of SoundDecibels Boeing 747140
Civil Defense Siren130 Jack Hammer120 Rock Concert110 Lawn Mower100
Motorcycle90 Garbage Disposal80 Vacuum Cleaner70 Normal
Conversation60 Light Traffic50 Background Noise40 Whisper30 For
every increase in 10 Decibels, the loudness DOUBLES!
Slide 18
Timbre Harmonic Content of sound Attack and Decay of sound
Vibrato Periodic changes in the frequency/amplitude
Slide 19
The of sound.
Slide 20
Diffraction of Sound
Slide 21
Refraction of Sound
Slide 22
Daytime refraction of sound due to ground temperature being
higher than air
Slide 23
Nighttime refraction of sound when ground cools off quickly but
warm air from the day stay in the air.
