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Radio production worktext
Analog to Digital Analog signal – continuously variable
electrical signal whose shape is determined by the shape of the sound produced. 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
Resource http://www.adobe.com/products/audition/pdfs/a
udaudioprimer.pdf
All analog measurements are on a continous line with no discreet points. Like drawing a line on a graph Reproduction of this signal can lead to
generation loss
Digital records the audio waveform as a series of samples consisting of discreet on and off points recorded as binary numbers. 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
Audio Sound passes through filters Low pass: eliminates high freqs above human hearing
Can be aliased or anti-aliased back into human hearing range
Audio is sampled many times per second Converted to (stored as) binary data Sample rate
32khz, 44.1 khz, 48khz Sample rate must be twice the highest audio frequency
to ensure high quality encoding Sound frequency example video:
http://videos.howstuffworks.com/hsw/19064-exploring-sound-frequency-explained-video.htm
Quantizing and coding 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
Coding assigns binary numbers to quantized samples
Computer based Plus some peripherals
2-track vs. multi-track software/hardware Some systems have both
PCI-slot audio card USB I/O device Software
Pro tools, audition, logic, sound forge, audacity
Sound files Ability to mark a region
Non-destructive editing Multi-track recording Transport controls Timeline
Digital Audio Workstations Computer Hard drive Software interface I/O hardware
Examples Pro tools, Logic
Software that work with off-the-shelf hardware Cakewalk Sonar, m-audio ozone (pro tools m-
powered)
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 00;00;00;00 = hours;minutes;seconds;frames
Improved audio signal quality Superior tech specs
Frequency response Signal to noise ration Reduced wow and flutter
Non-destructive editing Copies of edits Undo Easy edits and effects More time and energy spent on creative
metadata
Learning curve Loss of “warm” sound Equipment noise
Fans, HDs
DAWs Production On-air playback Logging bookkeeping
Sound signal Produced naturally, such as a voice or an
instrument Audio signal
Produced from an audio device such as a recorder, computer, or MIDI
Sound defined 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.
Resources
Volume measured in decibels Frequency = pitch; faster = higher
Cycles per second measured in hertz and kilohertz
Pure tone is a sine wave Without overtones
Fundamental Voice waveform with timbre, or
combination of many fundamentals