Radio production worktext. Analog to Digital Analog signal – continuously variable electrical...

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