Transcript Rtv1240c chap 2

Radio production worktext
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Analog to Digital
Analog signal – continuously variable electrical
signal whose shape is determined by the shape
of the sound produced.
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An electromagnetic representation of the sound
wave can be stored on electromagnetic tape.
 Mic>sound pressure>changes in voltage strength>mic
cable>recorder>records changes as changes in
magnetic strength
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Resource
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http://www.adobe.com/products/audition/pdfs/a
udaudioprimer.pdf
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All analog measurements are on a continous
line with no discreet points.
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Like drawing a line on a graph
Reproduction of this signal can lead to generation
loss
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Digital records the audio waveform as a series of
samples consisting of discreet on and off points
recorded as binary numbers.
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Computers associate these binary numbers to letters of
the alphabet and numbers, then computers manipulate
these binary numbers.
Analog to digital – analog can be converted to
digital by the following four stages:
Filtering
 Sampling
 Quantizing
 Coding
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Audio Sound passes through filters
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Low pass: eliminates high freqs above human hearing
 Can be aliased or anti-aliased back into human hearing range
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Audio is sampled many times per second
Converted to (stored as) binary data
 Sample rate
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 32khz, 44.1 khz, 48khz
 Sample rate must be twice the highest audio frequency to
ensure high quality encoding
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Sound frequency example video:
 http://videos.howstuffworks.com/hsw/19064-exploring-
sound-frequency-explained-video.htm
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Quantizing and coding
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Makes amplitude samples into manageable, discreet
numbers
 Bit depth is the max number of “steps” or levels
between measurements/conversions
 1-bit = two steps (on or off)
 16-bit = 65K+ values
 Higher bit-depth = higher fidelity
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Coding assigns binary numbers to quantized
samples
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Computer based
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2-track vs. multi-track software/hardware
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Plus some peripherals
Some systems have both
PCI-slot audio card
USB I/O device
Software
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Pro tools, audition, logic, sound forge, audacity
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Sound files
Ability to mark a region
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Non-destructive editing
Multi-track recording
Transport controls
Timeline
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Digital Audio Workstations
Computer
 Hard drive
 Software interface
 I/O hardware
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Examples
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Pro tools, Logic
Software that work with off-the-shelf hardware
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Cakewalk Sonar, m-audio ozone (pro tools mpowered)
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Timing of reading audio “words” to a common
clock to avoid pops and clicks when switching
between unsynchronized audio sources
MIDI (musical instrument digital interface) –
allows digital audio equipment to
communicate (“talk” to each other)
SMPTE (society for motion picture and
television engineers) – timecode
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00;00;00;00 = hours;minutes;seconds;frames
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Improved audio signal quality
Superior tech specs
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Frequency response
Signal to noise ration
Reduced wow and flutter
Non-destructive editing
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Copies of edits
Undo
Easy edits and effects
More time and energy spent on creative
metadata
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Learning curve
Loss of “warm” sound
Equipment noise
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Fans, HDs
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DAWs
Production
 On-air playback
 Logging
 bookkeeping
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Sound signal
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Produced naturally, such as a voice or an instrument
Audio signal
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Produced from an audio device such as a recorder,
computer, or MIDI
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Sound defined
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Sound is a mechanical wave which results from the
back and forth vibration of the particles of the
medium through which the sound wave is moving.
If a sound wave is moving from left to right through
air, then particles of air will be displaced both
rightward and leftward as the energy of the sound
wave passes through it. The motion of the particles
are parallel (and anti-parallel) to the direction of the
energy transport. This is what characterizes sound
waves in air as longitudinal waves.
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Resources
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Volume measured in decibels
Frequency = pitch; faster = higher
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Pure tone is a sine wave
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Cycles per second measured in hertz and kilohertz
Without overtones
Fundamental
Voice waveform with timbre, or combination of
many fundamentals