Audio Introduction PowerPoint

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Recording
Arts…Audio
Fall 2014
Range of Human Hearing
20 Hz – 20,000 Hz
or
20 Hz – 20 kHz
Range of Hearing
http://www.youtube.com/watch?v=2G9Q-r2leyw
Ear Training
http://homerecording.about.com/od/homestudiobasi
cs/a/test_tones.htm
The Mosquito Hearing Device
http://www.youtube.com/watch?v=eoa8eSf2NgQ&N
R=1
Sound Waves
• Sound is a longitudinal wave which can travel
through gases (air), liquids (under water) or solids (the
Earth).
• Sound cannot travel through a vacuum. In space no
one can hear you scream.
• When an object vibrates (moves backwards and
forwards) in air it produces sound waves.
Sound Waves
• The sound wave will have the same frequency as
the frequency of the vibrating object which made
it.
• The speed of a sound wave depends on the density
of the medium (substance) through which it is
traveling.
• Sound will travel faster through the Earth than under
water, and faster under water than it will in air.
The Speed of Sound
~344 meters per second
or
1130 feet per second
at
70 degrees F
Sound is a very slow energy, much slower than Light
Sonic BOOM!
This is what happens
when you exceed the
speed of sound…a
visual and audible
event…
http://www.youtube.com/wa
tch?v=6o0zmafxTmE
Loudness and Pitch
• The loudness of sound depends on the amplitude of
the wave. The bigger the amplitude, the louder the
sound.
• The pitch of sound (how high or low the note is)
depends on the frequency of the wave. The higher
the frequency, the higher the pitch.
Sound Waves
Frequency:
Frequency is defined as "the number of complete cycles
(complete waves) in one second".
Hertz is the unit of frequency (symbol Hz).
1 Hertz = 1 cycle per second.
Wavelength
• Wavelength = Speed of Sound / Cycles per second
• Vocalist sings the note A at 440 Hz.
o 1130 / 440 = 2.56 ft or 30.72 inches
• Low E on Electronic Bass ~ 40 Hz
o 1130 / 40 = 28.25 ft or 339 inches
• Screaming Guitar Lead @ 1175 Hz
o 1130 / 1175 = .96 ft or 11.5 inches
Decibels AUDIO
A logarithmic unit to measure volume/sound pressure..
• 0 db is the threshold of hearing
• 10 db is 10 times greater
• 20 db is 100 times greater
• 30 db is a 1000 times greater
• Threshold of Hearing (TOH) 0 dB
• Rustling Leaves 10 dB
• Whisper 20 dB
• Normal Conversation 60 dB
• Busy Street Traffic 70 dB
• Vacuum Cleaner 80 dB
• Large Orchestra 98 dB
• Level Front Rows of Rock Concert 110 dB
• Threshold of Pain 130 dB
• Military Jet Takeoff 140 dB
• Instant Perforation of Eardrum 160 dB
• Vaccum Cleaner 80db
• Rock Concert 110 db
• Difference of 30 db or 1000 times louder
• Therefore the average rock concert is equal to
listening to 1000 vacuum cleaners running at the
same time
• What is the speed of sound?
1,130 feet per second
• What is the range of human hearing?
20 Hz – 20 KHz (20,000 Hz)
• When you ear hears an increase of 10db in a sound,
how many times louder did that sound get?
10x
• What if there was an increase of 20db?
100x
• What about 30db?
1,000x
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