Phasing and sound envelope

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Sound Envelope
How the sound changes over time
Attack Time
How the sound comes in
Release/Decay time
How the sound ends/exits/dies
Acoustics
How sound behaves in air
2 ways to tell direction of sound w/ ears
1. Intensity difference between two ears
2. Arrival time difference
Early Reflections
First sounds in 30-50 milliseconds; support direct sound, fullness
Haas Effect
All sound reflections that hit your ear within 30-50 milliseconds your brain interprets as one event
Precedence effect
Brain interprets all early reflections as coming from the same direction as original sound
Types of sound
Direct sound, early reflections, reverb, echo
Direct sound
Directly from source to ear; clarity, directionality
Reverb/Reverberation
Sound bounces for > 30-50 milliseconds; sound hangs in the air and/or bounce around the room after initial sound finishes
Echo
1 or more distinct repetitions of the sound
Dead room
Absorb sound; reverb time < .5 sec
Live room
Reflected sound; reverb sound > .5 sec
Can reflected sound be added?
YES
Can reflected sound be removed?
NO
Recording room: dimensions
Dimensions cannot be divisible by the same number
Recording room: surfaces
NO parallel surfaces; supports flatness; parallel surfaces change frequency response
Recording room: sound isolation
Keep outside sound out, inside sound in
Phase
The relationship between two waves
Higher/lower wave
Amplitude
Wide/thin wave
Frequency
Shape of the wave
Tone, waveshape
In phase
Reinforce one another; constructive interference
Wave in positive
Compression
Wave in negative
Rarefaction
Out of phase
Destructive interference; signal gets weaker
180 degrees out of phase
Total cancellation/silence
Symptoms of phasing problem
1. Bringing up 2nd mic & sound gets softer
2. Bass gets attenuated
3. High frequencies get metallic-y sound
3:1 rule
Mics must be 3x the distance from each other as they are from the source (to avoid phasing issues)
Avoid phasing with speakers
Make sure they're wired the same
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