Audio Recording And Production: An Introduction Soam Acharya CS 731 Spring 1998

Contents sound basics acoustics/psycho-acoustics actual recording process

Characterizing Sound Frequency and Pitch Amplitude and Loudness Frequency and Loudness Acoustic Phase Timbre

Frequency And Pitch Hz –“feel” outside this range low bass: Hz –traffic, thunder, explosions upper bass: Hz –fullness/boomy –rhythm instruments: drums, bass, low piano midrange: Hz –fundamental of most sound sources –intensity upper midrange: Hz –highest sensitivity treble: Hz –brilliance/sparkle

Amplitude and Loudness db-SPL = 20 * log 10 (sound pressure/ref. sound pressure) can hear loudness at or greater the db type measurement also used frequently elsewhere

Amplitude and Loudness II Threshold of hearing Furnished living room Subdued conversation Average conversation 1” away from acoustic guitar subway Threshold of pain: thunder, “in your face” vocals Airport runway, inside a bass drum dB- SPL

Frequency and Loudness [p23 - fig 2-7] (in)equal loudness principle masking equalization

Timbre Tone quality or color

Timbre II Shape of sound or envelope

Acoustics/Psycho-acoustics direct waves early reflection later reflection (reverberation) –body –decay or reverberation time echo –long reflection path

Sound In An Enclosed Room P

Reverberation Vs. Decay Time Reverberation Decay Time Concert hall gymnasium Inside a car closet Conference room living room w. rugs Tiled bathroom Open field

Surface Shape of Room Parallel: standing waves Concave: concentrate Concave: disperse

Studio Room Surface P

Studio Room Materials Sound absorption coefficient –0 reflects, 1 absorbs –drapes > glass porous absorbers –acoustical tiles, carpets, fibreglass, urethane foams bass taps (diaphragmatic absorbers) –wood panels mounted over air space

Actual Recording Process playback Sound to electric signal Analog processing/mixing analog to digital Processing/editing storage Computer digital to analog

Converting Sound to Electricity: Microphones moving coil –diaphragm, magnet, coil in a magnetic field –robust, not sensitive to transients, less expensive ribbon microphone –metal ribbon in a magnetic field printed ribbon –more robust design –good high frequency response –low output level ie. not sensitive

Capacitor/Condenser Microphone Needs separate power supply for pre-amp –electret type: pre-charged, can get away with batteries professional use high sensitivity, output level (large SNR) Back plate spacer Air film Diaphragm - front plate

Microphone Pickup Patterns Omnidirectional –all over –non directional Bidirectional –front and rear Unidirectional –front only –cardioid –unidirectional

Pickup Patterns II

Pickup Patterns III P

Reading A Microphone Spec. polar response diagram Cardioid

Reading a Microphone Spec II Frequency response plot

Proximity Effect of Mic. Relative level (dB) frequency 1/4” from mic 2” from mic

Microphone Accessories I windscreen Pop-screen

Microphone Accessories II XLR -male XLR-female 1/4” RCA 3.5 “ (miniplug)

Specialty Microphones lavalier shotgun parabolic wireless

Lavalier Microphones To be worn on lapels omnidirectional built-in high freq. boost (chin cutoff)

Wireless Microphones FM transmitter UHF/VHF FCC approved multiple modes

Shotgun Microphones Long distance pickup –need for unobtrusiveness on sets attenuate sound from all angles except a narrow one in the front supercardioid/hypercardioid/ultracardioid less directional at lower freq.s

Parabolic Microphones Also long-distance pickup omni/uni directional microphone

Deploying Microphones Acoustic/electrical phases omnidirectional vs. unidirectional miking speech for radio miking speech for tv recording music reducing unwanted sounds

Acoustic/Electrical Phases Acoustic phases cancellation –3:1 rule for microphones dist between two microphones >= dist between source and main microphone P

Omni vs. Uni directional Omni –does not have to be held directly in front –picks up more ambience –less susceptible to wind, popping –more resilient to distance Uni –cuts down unwanted sound –no sense of environment –reduces feedback in reverberant locations

Miking Speech in Radio Stay within pickup pattern mic-to-source distance –inverse square law –proximity weak voice lip smacking diffusion of sound quality

Miking Speech in Radio II Across directional mic face reduces freq. response 45 deg. angle P P

Stereo Miking Two microphones –difference in arrival time between microphones phase problems when combining to mono Coincident miking –two directional microphones together on same vertical axis –minimize disparity in arrival times

Stereo Miking II P 304, 12-13

Miking for TV News and interviews Panel and talk programs miking the audience

News and Interviews –Omnidirectional lavalier hide under clothes –rustling/movment –inhibits higher frequencies

Panel and Talk Programs Host/guest: –Lavalier microphones unobtrusive easy to mount mic-source constant Mobile host –handheld pop filter/ shock mount host can control source distance go to audience

Miking Audience Directional shotgun microphones –distribute them in equal quadrants above the audience audience monitor loudspeaker feedback –offaxis to microphones

Recording Music Distant miking –ensemble, reduces electronic noise –air loss with distance: freq dependent –phase close miking –control –better separation of sources

Recording Music II Miking instruments –drums bass drum: coil damping hi-hat: capacitor –violin/viola multiple microphones to capture the range –vocals proximity effect sibilance compression

Putting It Together P

Reducing Noise Microphone location –near noisy sources outdoor location: –noise suppressors (eq dialogue) shielding noise gates

Roadmap Sound to electric signal Analog processing/mixing analog to digital Processing/editing storage Computer digital to analog

Analog Processing/Mixing

Analog Processing/Mixing II Input: –overload indicator –trim –phantom power –equalizer/filter –phase reversal –panning –bus assignment (input signals to output buses) –cuing (for auditioning) –meters –mute

Analog Processing/Mixing III Output: –buses (to group signals) –bus fader –effects modules –output meter

Patch Panel P , 6-12

Roadmap Sound to electric signal Analog processing/mixing analog to digital Processing/editing storage Computer digital to analog

Soundcards inputLow pass sampling A/D D/A Low pass output D/A

Soundcard Problems Poor quality: 80dB SNR as opposed to >90 dB SNR value for CD players background hissing noise –mute unwanted sources into soundcard humming noise when connected to hifi –ground loop hissing from microphones –noisy mic preamps

Soundcard Problems II Distortion during playback –clipping in the mixer chip

Roadmap Sound to electric signal Analog processing/mixing analog to digital Processing/editing storage Computer digital to analog

Processing spectrum signal processors –equalizers, filters time signal processors –reverb, delay amplitude processors –compressors/limiters, expanders/noise gates

Spectrum Signal Processor Equalization frequency gain Turnover freq. stop freq. Max boost. Max cut. High frequency

Spectrum Signal Processor II Graphic equalizer: fixed frequency Parametric: variable frequency

Spectrum Signal Processors III Filters: –high pass –low pass –bandpass –notch

Time Signal Processors Reverb Delay –doubling –chorus –slap back

Time Signal Processors II Flanging –double sound source, delay one, mix delay sound

Time Signal Processors III Phasing –double sound source, phase shift one, mix Phase shift sound

Time Signal Processors IV Pitch shift –time compression

Amplitude Processors Compressors and limiters P 234, 9-25

Amplitude Processors II Noise gates P 238, 9-28

Editing: Cubase VST The Transport Bar

Editing II Arrangement Window

Editing III The Parts Display

Editing IV The Audio Mixer Window

EQ and Effect Windows

The Audio Pool

Audio editor Wave editor

Midi Editing