General Audio Theory

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3 Types of sound

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Production (physical) - sound being produced by somethingPropagation (physical) - sound moving across a distancePerception (psychological) - sound being perceived by a person, microphone, etc.

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Sound (definition)

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Movement of air molecules through a mediumSound requires a mediumNo sound exists in a vacuumSound travels faster in denser mediaAffected by temperature and pressure (warmer = faster)

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Speed of Sound

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1130 ft per second

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Sound can be...

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ReflectedDiffusedDiffractedRefracted

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Amplitude

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Measures Sound Pressure Level (SPL)

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SPL

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Sound Pressure LevelRelative change above and below atmospheric pressure caused by the presence of sound

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Frequency

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Perceived pitch of a soundMeasurement of the number of cycles per secondHz1000 Hz = 1 kHz

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Human Hearing Range

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20Hz - 20kHz

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Tonal Waveforms

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Waveforms with clear fundamentalWaveforms with unclear fundamental or multiple fundamentals

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Acoustics

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Study of how materials affect sound transmission

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The 3 sound fields in every recording studio are...

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Direct SoundReflectionsReverberations

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Direct Sound

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Shortest path from source to receiver

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Reflections

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When sound interacts with surface then gets to receiver

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Reverberation

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Time it takes for sound to lose all of its energy after reflecting off everything

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Equal Loudness

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Perceived frequency is determined by volumeHumans don't hear all frequencies equally

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Human hearing sensitivity is highest in ...

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500Hz - 5000Hz Range

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Masking

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Loud sounds cover up quieter sounds

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Audio (definition)

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Representation of sound on a non-acoustic medium

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Recording (definition)

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The process of converting audio signal into form stored on media track - physical location (or metaphor) of recorded audio on media

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Noise Ceiling

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The upper limit of dynamic range

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Noise Floor

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Can't hear most things below the noise floorThe lower limit of dynamic range

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Analog

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Continuous representation of data

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Digital

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Discrete sampling

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Sampling Rate

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Number of discrete measurements over regular time interval

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CD Quality Sampling Rate

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44,100Hz

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Bit Depth

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Length of discrete values measurement can produce

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CD Quality Bit Depth

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16 bits per second

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Nyquist Shannon Theorem

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Audio signals containing frequencies between 0 and Sx2 Hz can be represented using S samples per second

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Aliasing

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Occurs when the rules of the Nyquist Shannon Theorem are broke

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Amplitude Quantization

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Represents amplitude value at each instantLimited by the resolution of the system

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Panorama

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Sound represented in stereoLeft + Right = Phantom CenterPanning puts mono sound somewhere in between only left and only right

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5 Elements to a Good Mix

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BalancePanoramaFrequency RangeDimensionDynamics

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Dynamic Range

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Difference between highest and lowest

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Frequency Range

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Distribution of highs, mids, and lows

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Spatial Dimension

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Distance

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Temporal Dimension

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How edits were spaced over time

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TEMP Tracks

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Existing tracks inserted for editing, pacing (tempo), mood, or feel (key)Often used as placeholders to be replaced by more qualified editors.

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VO using software General Workflow

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1. Setup physical aspects of equipment2. Setup software aspects3. Check levels4. Record/Log5. Export Results6. Clean up and shut down

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Biggest problem with video game audio integration

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Sound designers are not programmersProgrammers are not sound designersMiddleware is used to export audio files with code so that programmers can insert it 

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Digital Recording Studio Requirements

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Computer + SoftwareHardware InterfaceMicrophone PreampMonitorsCabling

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Dynamic vs. Condenser Microphone

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Dynamic - Self powered, less sensitiveCondenser - Needs more power, more sensitive

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Phantom Power

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+48V sent across both wiresRuns over standard XLR cables

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Polar Pattern

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Description of varying input sensitivity based on directionality

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Polar Pattern Directions

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OmniFigure 8CardiodBidirectionalHypercardiod

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Preamp

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Single microphone amplification channelConverts mic level to line level

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Balanced Cabling 

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2 Rings (TRS, XLR)Good for long cable runs, built to reduce noiseMore expensive

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Unbalanced Cabling

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1 Ring (TS, RCA)Does not reduce noise

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Mastering (3 steps)

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1.Consolidating source material to single master copy. Master copy used as the source for duplication2. Arranging multiple tracks/sources and adjusting volume so they appear as one consistent program3. Adjusting the tone of a track or set of tracks to finalize the sound equally

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Relative Levels

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Refers to the balance of levels of multiple tracks so that all audio information is present and focus elements are perceived with priority

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Absolute Levels

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The final output of all tracks with respect to 0dBfs (when digital)

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Thresholds

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Point in dBf's where compression begins

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Ratio

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Determines how many input dB results in an output4:1 = for every 4 dBF's input there is a 1dBf's output

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Attack

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How long (in ms) before compression reaches full value after threshold is breached

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Release

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How long (in ms) before compression reaches no value after threshold is breached

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Gain

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Used to raise gain after reduction