Transcript Week 10 - Truth Recordings

WEEK 10
Reverberation parameters and concepts
Absorption co-efficient
Reverberation
The persistence of sound in a space
after the original sound has stopped
Closely spaced echoes decaying over
time
Reverberation
Reverb characteristics are determined
by the dimensions of a room, the
construction materials and the shape of
the space
Reverb
Direct sound is the
original sound
Early Reflections
are the first
reflections you hear
after the direct
signal.
Direct Sound vs. Reflected Sound
RT60
RT60 is the time it takes for reverb to
drop 1/1,000,000 below the power of
the direct sound (or a drop of 60dB)
RT60
Reverberation
The optimum reverberation time for a
space in which music is played depends
on the type of music that is to be played
in the space. Rooms used for speech
typically need a shorter reverberation
time so that speech can be understood
more clearly.
Reverb
In 90 seconds write as many
descriptive words for reverb as
possible
Types of Reverb
Chamber
Spring
Plate
Digital Hardware
Software (Algorithmic)
Software (Convolution)
Studio Reverb History
1947 - The first creative use of artificial
reverb on a pop recording (reverb chamber)
Studio Reverb History
1957 – First plate reverb (EMT140)
1959 – Hammond A-100 with spring reverb
1973 – Roland Space Echo RE-200
1972 – EMT 144 Digital Reverb
1976 – EMT 250 Digital Reverb
1978 – Lexicon 224 Digital Reverb
Studio Reverb History
2001 – Altiverb release first convolution
reverb plug-in
Reverb Chambers
EMT 140 Plugin
Plate Reverb
Spring Reverb
Spring Reverb
Spring Reverb
EMT 250 Electronic Reverberator Unit
Reverb Parameters
Pre-delay is the amount of time before the
first reflection
Early reflections are the first group of
echoes (after the direct sound)
Decay Time is the time it takes for the
reverb to reduce by 60dB
Reverb Parameters
Mix is the parameter for mixing between the
‘dry’ and ‘wet’ signal
Dampening typically ‘dampens’ the high
frequency of the reverb
Diffusion mimics the scattering of sound in
all directions
CONVOLUTION
REVERB
Convolution Reverb
Software reverb which simulates real
physical acoustic spaces through the
use of recorded impulse responses
Convolution reverbs produce the
reverberant behaviour unique to a
particular acoustic space
Wallace Sabine
In the late 19th century,
Wallace Sabine investigated
the impact of absorption on
the reverb time.
Using a stopwatch and his
ears, he measured the time
from direct sound to
inaudibility. (roughly 60dB)
Absorption co-efficient
An ‘Absorption co-efficient’ tells us
how much sound a material will
absorb at a particular frequency.
It is a value of between 0 and 1
1 being completely absorbent
0 being completely reflective
Why do we like Absorption
Co-efficients?
They help us determine which
materials to use to build good
sounding studios
We can use the absorption co-efficient
values to calculate the reverberation
time of a room before its been built
Absorption co-efficients
Floor materials
125 Hz
250 Hz
500 Hz
1 kHz
2 kHz
4 kHz
carpet
0.01
0.02
0.06
0.15
0.25
0.45
Concrete
(unpainted,
rough finish)
0.01
0.02
0.04
0.06
0.08
0.1
Concrete
(sealed or
painted)
0.01
0.01
0.02
0.02
0.02
0.02
Marble or glazed
0.01
tile
0.01
0.01
0.01
0.02
0.02
Vinyl tile or
linoleum on
concrete
0.03
0.03
0.03
0.03
0.02
0.02
Reverberation Formula
The formula for calculating the time it takes
for reverb to drop 60dB is:
RT60 = 0.161 (V/Sa)
V = Volume of the room
Sa = Total surface absorption of the
room expressed in Sabins
Calculating Sabins
Total absorption in Sabins can be calculated by:
A = S1α1 + S2α2 + S3α3...
A = the absorption of the room (m2 sabin)
Sn = area of the actual surface (m2)
αn = absorption coefficient of the actual surface
Next Week
Revision part 1