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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

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contents
Contents
  • sound basics
  • acoustics/psycho-acoustics
  • actual recording process
characterizing sound
Characterizing Sound
  • Frequency and Pitch
  • Amplitude and Loudness
  • Frequency and Loudness
  • Acoustic Phase
  • Timbre
frequency and pitch
Frequency And Pitch
  • 20 - 16000 Hz
    • “feel” outside this range
  • low bass: 20 - 80 Hz
    • traffic, thunder, explosions
  • upper bass: 80 - 320 Hz
    • fullness/boomy
    • rhythm instruments: drums, bass, low piano
  • midrange: 320 - 2560 Hz
    • fundamental of most sound sources
    • intensity
  • upper midrange: 2560 - 5120 Hz
    • highest sensitivity
  • treble: 5120 - 20000 Hz
    • brilliance/sparkle
amplitude and loudness
Amplitude and Loudness
  • db-SPL = 20 * log10 (sound pressure/ref. sound pressure)
  • can hear loudness at 1 - 10000000 or greater
  • the db type measurement also used frequently elsewhere
amplitude and loudness ii

Airport runway, inside a bass drum

Threshold of pain: thunder, “in your face” vocals

subway

1” away from acoustic guitar

Average conversation

Subdued conversation

Furnished living room

120

100

80

20

40

140

60

Threshold of hearing

0

Amplitude and Loudness II

dB-SPL

frequency and loudness
Frequency and Loudness

[p23 - fig 2-7]

(in)equal loudness principle

masking

equalization

timbre
Timbre

Tone quality or color

timbre ii
Timbre II

Shape of sound or envelope

acoustics psycho acoustics
Acoustics/Psycho-acoustics
  • direct waves
  • early reflection
  • later reflection (reverberation)
    • body
    • decay or reverberation time
  • echo
    • long reflection path
reverberation vs decay time
Reverberation Vs. Decay Time

Decay

Time

Concert hall

gymnasium

Conference room

living room w. rugs

Inside a car

closet

Tiled bathroom

Open field

Reverberation

surface shape of room
Surface Shape of Room

Concave:

concentrate

Concave:

disperse

Parallel:

standing waves

studio room materials
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

Sound to

electric signal

Analog processing/mixing

Computer

analog to digital

storage

digital to analog

Processing/editing

Actual Recording Process

playback

converting sound to electricity microphones
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

spacer

Back plate

Air film

Diaphragm -

front plate

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)
microphone pickup patterns
Microphone Pickup Patterns
  • Omnidirectional
    • all over
    • non directional
  • Bidirectional
    • front and rear
  • Unidirectional
    • front only
    • cardioid
    • unidirectional
reading a microphone spec
Reading A Microphone Spec.

Cardioid

polar response diagram

reading a microphone spec ii
Reading a Microphone Spec II

Frequency response plot

proximity effect of mic

1/4” from mic

2” from mic

frequency

Proximity Effect of Mic.

Relative

level (dB)

microphone accessories i
Microphone Accessories I

windscreen

Pop-screen

microphone accessories ii
Microphone Accessories II

XLR -male

XLR-female

3.5 “

(miniplug)

RCA

1/4”

specialty microphones
Specialty Microphones
  • lavalier
  • shotgun
  • parabolic
  • wireless
lavalier microphones
Lavalier Microphones
  • To be worn on lapels
  • omnidirectional
  • built-in high freq. boost (chin cutoff)
wireless microphones
Wireless Microphones
  • FM transmitter
  • UHF/VHF FCC approved
  • multiple modes
shotgun microphones
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
Parabolic Microphones
  • Also long-distance pickup
  • omni/uni directional microphone
deploying microphones
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/Electrical Phases
  • Acoustic phases cancellation
    • 3:1 rule for microphones
      • dist between two microphones >= dist between source and main microphone

P 292 12-1

omni vs uni directional
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
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

Miking Speech in Radio II

P 297 12-5

P297 - 12-6

stereo miking
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
Stereo Miking II

P 304, 12-13

miking for tv
Miking for TV
  • News and interviews
  • Panel and talk programs
  • miking the audience
news and interviews
News and Interviews
  • Omnidirectional lavalier
    • hide under clothes
      • rustling/movment
      • inhibits higher frequencies
panel and talk programs
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
Miking Audience
  • Directional shotgun microphones
    • distribute them in equal quadrants above the audience
  • audience monitor loudspeaker feedback
    • offaxis to microphones
recording music
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
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
Putting It Together

P 409 - 14-67

reducing noise
Reducing Noise
  • Microphone location
    • near noisy sources
  • outdoor location:
    • noise suppressors (eq dialogue)
  • shielding
  • noise gates
roadmap
Roadmap

Sound to

electric signal

Analog processing/mixing

Computer

analog to digital

storage

digital to analog

Processing/editing

analog processing mixing ii
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
Analog Processing/Mixing III
  • Output:
    • buses (to group signals)
    • bus fader
    • effects modules
    • output meter
patch panel
Patch Panel

P141 - 6-11, 6-12

roadmap52
Roadmap

Sound to

electric signal

Analog processing/mixing

Computer

analog to digital

storage

digital to analog

Processing/editing

soundcards
Soundcards

A/D

sampling

input

Low pass

D/A

D/A

output

Low pass

soundcard problems
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
Soundcard Problems II
  • Distortion during playback
    • clipping in the mixer chip
roadmap56
Roadmap

Sound to

electric signal

Analog processing/mixing

Computer

analog to digital

storage

digital to analog

Processing/editing

processing
Processing
  • spectrum signal processors
    • equalizers, filters
  • time signal processors
    • reverb, delay
  • amplitude processors
    • compressors/limiters, expanders/noise gates
spectrum signal processor
Spectrum Signal Processor
  • Equalization

gain

High frequency

Max boost.

frequency

Max cut.

Turnover freq.

stop freq.

spectrum signal processor ii
Spectrum Signal Processor II

Graphic equalizer: fixed frequency

Parametric: variable frequency

spectrum signal processors iii
Spectrum Signal Processors III
  • Filters:
    • high pass
    • low pass
    • bandpass
    • notch
time signal processors
Time Signal Processors
  • Reverb
  • Delay
    • doubling
    • chorus
    • slap back
time signal processors ii
Time Signal Processors II
  • Flanging
    • double sound source, delay one, mix

sound

delay

slide63

Time Signal Processors III

  • Phasing
    • double sound source, phase shift one, mix

sound

Phase

shift

time signal processors iv
Time Signal Processors IV
  • Pitch shift
    • time compression
amplitude processors
Amplitude Processors

Compressors and limiters

P 234, 9-25

amplitude processors ii
Amplitude Processors II

Noise gates

P 238, 9-28

editing cubase vst
Editing: Cubase VST

The Transport Bar

editing ii
Editing II

Arrangement

Window

editing iii
Editing III

The Parts Display

editing iv
Editing IV

The Audio Mixer Window

slide71

EQ and

Effect Windows

slide73

Audio

editor

Wave

editor