1. Reverberation parameters and concepts Absorption co-efficient
WEEK 10
Reverberation parameters and concepts
Absorption co-efficient
Reverberation parameters and concepts
Absorption co-efficients
Estimating reverb time

3. Reverberation
The persistence of sound in a space after the original sound has stopped
Closely spaced echoes decaying over time

4. Reverberation
Reverb characteristics are determined by the dimensions of a room, the construction materials and the shape of the space
Reverberation (abbrev. reverb) is the persistence of sound in a particular space after the original sound is removed. When sound occurs in an acoustic space, a large number of echoes build up and then slowly decay.

6. Reverb Direct sound is the original sound
Early Reflections are the first reflections you hear after the direct signal.

7. Direct Sound vs. Reflected Sound

9. 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)

11. RT60

12. 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.
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.

13. In 90 seconds write as many descriptive words for reverb as possible
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.

14. Types of Reverb
Chamber
Spring
Plate
Digital Hardware
Software (Algorithmic)
Software (Convolution)

15. Studio Reverb History
The first creative use of artificial reverb on a pop recording (reverb chamber)
t was UA's own Bill Putnam, Sr., who was the first to use artificial reverb creatively on a pop recording in 1947, with the use of the first reverb chamber (the studio bathroom!). The result was a huge hit by The Harmonicats called "Peg o' My Heart" on his own Universal label. Having the ability to control reverb amount and turn the effect on and off at will was a major breakthrough, and a big part of the record's sound. Bill went on to build dedicated chambers for his studio in Chicago, as well as his later LA studios. Chamber reverb is to this day a technological and architectural art all to itself. The sound he created captured the listening public's imagination, and artificial reverb was popularized as a production tool for the recording environment; but for most of the fifties, room recording and echo chambers were the only options.

17. 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
t was UA's own Bill Putnam, Sr., who was the first to use artificial reverb creatively on a pop recording in 1947, with the use of the first reverb chamber (the studio bathroom!). The result was a huge hit by The Harmonicats called "Peg o' My Heart" on his own Universal label. Having the ability to control reverb amount and turn the effect on and off at will was a major breakthrough, and a big part of the record's sound. Bill went on to build dedicated chambers for his studio in Chicago, as well as his later LA studios. Chamber reverb is to this day a technological and architectural art all to itself. The sound he created captured the listening public's imagination, and artificial reverb was popularized as a production tool for the recording environment; but for most of the fifties, room recording and echo chambers were the only options.

18. Studio Reverb History
2001 – Altiverb release first convolution reverb plug-in
t was UA's own Bill Putnam, Sr., who was the first to use artificial reverb creatively on a pop recording in 1947, with the use of the first reverb chamber (the studio bathroom!). The result was a huge hit by The Harmonicats called "Peg o' My Heart" on his own Universal label. Having the ability to control reverb amount and turn the effect on and off at will was a major breakthrough, and a big part of the record's sound. Bill went on to build dedicated chambers for his studio in Chicago, as well as his later LA studios. Chamber reverb is to this day a technological and architectural art all to itself. The sound he created captured the listening public's imagination, and artificial reverb was popularized as a production tool for the recording environment; but for most of the fifties, room recording and echo chambers were the only options.

19. Reverb Chambers

23. German company EMT made a breakthrough in 1957 with the release of the EMT 140, which utilized a resonating metal plate to create ambience.
The a plate reverb is made up of a large (2x3m), thin piece of sheet metal suspended from a steel frame by spring tensioners at each corner. An electrical transducer mounted to the center of the suspended plate induces plate movement, which creates the effect. One or two (mono or stereo) pickups are mounted to the plate as well, for the reverb return. A damping plate controlled by a servo motor, allowed adjustment of the reverb time. All of these simple elements were built into a heavy wooden enclosure.

24. German company EMT made a breakthrough in 1957 with the release of the EMT 140, which utilized a resonating metal plate to create ambience.
The a plate reverb is made up of a large (2x3m), thin piece of sheet metal suspended from a steel frame by spring tensioners at each corner. An electrical transducer mounted to the center of the suspended plate induces plate movement, which creates the effect. One or two (mono or stereo) pickups are mounted to the plate as well, for the reverb return. A damping plate controlled by a servo motor, allowed adjustment of the reverb time. All of these simple elements were built into a heavy wooden enclosure.

25. EMT 140 Plugin
German company EMT made a breakthrough in 1957 with the release of the EMT 140, which utilized a resonating metal plate to create ambience.
The a plate reverb is made up of a large (2x3m), thin piece of sheet metal suspended from a steel frame by spring tensioners at each corner. An electrical transducer mounted to the center of the suspended plate induces plate movement, which creates the effect. One or two (mono or stereo) pickups are mounted to the plate as well, for the reverb return. A damping plate controlled by a servo motor, allowed adjustment of the reverb time. All of these simple elements were built into a heavy wooden enclosure.

26. The sound is dense, with heavy diffusion. The sound is wonderful, warm, open, and natural.

27. Plate Reverb

28. Spring Reverb

29. Spring Reverb

30. Spring Reverb

31. EMT 250 Electronic Reverberator Unit – 1976
Pre-delay controls and high and low frequency decay times
Really the first multi effects unit

32. EMT 250 Electronic Reverberator Unit
Pre-delay controls and high and low frequency decay times
Really the first multi effects unit

52. 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

53. 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

58. CONVOLUTION REVERB

62. 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

67. 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)
He found that the reverberation time is proportional to the dimensions of room and inversely proportional to the amount of absorption present.

68. 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
The attenuation coefficient is a quantity that characterizes how easily a material or medium can be penetrated by a beam of light, sound, particles, or other energy or matter. A large attenuation coefficient means that the beam is quickly "attenuated" (weakened) as it passes through the medium, and a small attenuation coefficient means that the medium is relatively transparent to the beam. Attenuation coefficient is measured using units of reciprocal length.
The attenuation coefficient is also called linear attenuation coefficient, narrow beam attenuation coefficient, or absorption coefficient. Although all four terms are often used interchangeably, they can occasionally have a subtle distinction, as explained below.

69. 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

70. 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)
0.04
0.08
0.1
Concrete (sealed or painted)
Marble or glazed tile
Vinyl tile or linoleum on concrete
0.03

71. Reverberation Formula
The formula for calculating the time it takes for reverb to drop 60dB is:
RT60 = (V/Sa)
V = Volume of the room
Sa = Total surface absorption of the room expressed in Sabins

72. Calculating Sabins A = S1α1 + S2α2 + S3α3...
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

73. Next Week
Revision part 1