254-week 5

8/7/2019 254-Week 5

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MTA 254

• Syllabus change: Lynda.com is now optional!

$25 month, or see me after class / in lab for discount.

• TA Theater will take place Week of April 4

• Not changed: Archival Project due Week of April 11

(in lab.)• Not changed: ADR Project due Week of April 25

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MTA 254

MIDTERM EXAM is Next Monday in this room!

• Labs / Lectures are fair game!

In lab this week: bring your harddrive to get the

footage for the Archival Project

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Analog vs. Digital

• Why digital? (Sound is, of course, analog)

• the choice of how to record depends on what

we are going to DO with it.

• All recording, analog or digital, involves changingair pressure into voltage, then reversing theprocess.

• We use digital recording b/c in post productionwe need to make lots of copies, and digitalcopies don’t degrade.

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Turning Sound to Digital

• To make a digital recording, we need to take

snapshots to convert the changing voltages intonumbers. These are called samples .

• How many snapshots we take = sample rate .

• The accuracy of each sample, like the dpi of adigital photo = bit depth .

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Sample Rate & Bit Depth

SAMPLE RATE describes how many snapshots persecond we take.

•The most common rates are 44.1k and 48K. Rememberthe Nyquist theorem: You need twice the number of samples as the highest frequency you wish to record.20K x 2 = 40,000 (+ 10% for good measure) = 44.1K

BIT DEPTH describes the accuracy of oursnapshots.

• The standard for professional digital audio is 16 bit, whichoffers 65,536 possible different values for each sample.

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• To make an audio le smaller, you could cut bit depthand sample rate. The le would be smaller, but itwould sound worse.

• Delta encoding (Quicktime) recognizes incrementalchanges between samples.

•Mp3 is a type of perceptual encoding . It eliminatessounds that are masked, or redundant. The process is“lossy” but you don’t notice it (as much).

Audio Compression

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• There are two standards for “normal” line levelvoltages: “+4” (hot!) for pro gear, “-10” (warm) for

consumer gear.

• Pro to Consumer will distort. Consumer to Pro willbe noisy (but ok). (Plugging into a sound board?)

• There is balanced and unbalanced wiring. Balanced(like most XLRs) rejects noise and interference.RCA plugs are unbalanced.

Audio on a Wire

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(Basic) Audio Sweetening

• “Sweetening” is audio-speak for processing sound

to make it sound “better.”

• Until recently, sweetening meant processing youranalog signal with an external analog device.

• Now, many of these devices are “plug-ins” one canaccess via one’s audio processing software.

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Using Audio Processors

EQ, Noise Reduction, Compression, Reverb

• These tools are easy way to ruin your audio, or make

people sound like robots.• Too much processing sounds worse than marginal audio--

always do a before and after.

•For example: reducing noise is what you’re striving for--noteliminating it.

• Usually, when you nd a setting that sounds good, back off it a bit to reduce the effect.

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Equalization (EQ)

• If you’re going to learn one audio processing tool, this isit. Some form of EQ is on almost every audio softwaredevice.

• Denition: Boosting and/or cutting the volume of certain frequencies on the track(s) in question.

• Bass and treble knobs, for example, or that cool “EQ”

on an old boombox, are cheap, lousy EQs.• Two main uses: Surgical & Shaping

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Surgical EQ means to precisely reduce an unwantedsound by sharply cutting its frequency. For example, to

lessen the rumble of a passing truck.• Usually applied to a specic region of audio as a “x.”

Shaping EQ is a more subtle process applied to an entiretrack to make it t with other tracks.

• In Pro Tools: Shaping EQ usually applied in the mixwindow; Surgical EQ in the edit window.

Surgical EQ and Shaping EQ

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• Cut off everything below 90Hz. Try a gentle peak around

240Hz for warmth, and a similar boost around 1.8kHz forintelligibility. A sharp dip around 5kHz can help sibilance.

• Help muddy dialog with a cutoff below 150Hz, and a 3-6dBboost around 2kHz.

• To nd and eliminate an annoying sound do an EQ“sweep.” (We will practice this in a future lab.)

Standard Dialog Equalizer Tips:

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• The “Holy Grail” of audio processing. (Like the ctitious

“magic box” in the scene from The Conversation.)• NR tries to identify the noise pattern and sharply cut

only those frequencies, leaving dialog unchanged.

•It’s VERY EASY to create a worse sounding track usingNR--use it very lightly, or your track will start to soundmetallic .

Noise Reduction

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• NOT data compression--this is NOT about making lessmaller.

• Denition: Reduce the dynamic range of a track inorder to make the soft sounds louder, while keeping theloud sounds from peaking.

• Used in pop music to create the “aircraft carrier” stylewaveform.

• Usually applied to an entire track, or the whole mix.

Compression

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• Denition: The simulation of sound reections

• It’s used to add “dimension” to sound.

• In lm sound, it’s usually applied to backgroundambience, walla, or effects tracks rather than voices.

• Software settings mimic different room sizes: church,

hall, small room, etc.

Reverb

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Audio Processors in Music

• Music production uses these same processes(EQ, Compression, Reverb [usually not Noise Reduction]) incomplex yet subtle ways.

• Here is a clip from a tutorial DVD by a Grammy winningproducer showing some very basic strategies in mixing thelead vocals of a record:(It is unclear why he is crouching behind a display case...)

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254-week 5

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