How to do a RT60 Calcuation

Contents:

  - Introduction
  - Absorbtion Coefficients
  - Mounting and Placement
  - RT60 Calculation How
  - RT60 Calculation Spreadsheet
  - Recommended Reverberation Time
  - Appendix
  - References



Introduction:

In a room there are direct sound and reverberant sound. When sound waves leave a speaker, they travel outward in a three dimensional sphere.

The Direct Sound is the sound path from a speaker directly to the listener.
This is the shortest path between the speaker and the listener, and so it will arrive first.


But sound can also reflect off of off a wall or floor or ceiling or other objects.


The Reverberant Sound Field is created by sound bouncing off multiple reflective surfaces and objects within the room, multiple times.


In an 8' by 15' by 20' room, in 1 second the sound will bounce at least 141 times. Sound travels at 1130ft/s, divided by 8', gives 141 bounces. Very quickly these reflections are arriving at the listener in a continous stream. They are so closely spaced that the ear is incapable of distinguising them as individual sounds.

With each bounce, some of the energy of that sound is lost, either by absorbtion (into an object/wall and even the air itself) or transmission (through an object/wall).

RT60 (also known as RT60, also known as T60, also known as Reverberation Time 60)
  is the time taken for the reverbarant sound to decay to one-millionth of its original intensity after the source has ceased. (i.e. 60dB of decay). see Decibel Table


Too much reverberation makes the music "muddy" or speech unintelligible. This is because the sound from so long ago is combining with and overriding a bunch of the direct sound. To little reverberation makes music "dry" or lifeless.

The solution to too much reverberation is to add absorbtion to the room, but the question is how much to add, and how much is already there, and at what frequencies.

At the turn of the last century (early 1900's), Wallace Clement Sabine gave us the following equation. Sabine is known as the father of the science of architectural acoustics. Absorbtion is measured in Sabins, and he designed Riverbank Acoustical Laboritories (built 1918). At the time Wallace was working on the RT60 of entire rooms, but around 1934 it was discovered that the same formula was effective for the effects of descrete parts of the room, as shown by Robert W. Young.

where:
  RT60 = reverberation time, in seconds
  V = volume of room, in cubic feet (or m^3)
  S = surface area, in square feet (or m^2)
  = average absorbtion coefficient

Of V, S, and , you probably know how to calculate V and S as soon as you know the dimensions (length, width, height) of your room.
But to save you time calculating V and S, just type your room dimensions into Room Modes Calculator and it will show you 
     Room Dimensions: Length=13.92 ft, Width=11.42 ft, Height=10 ft
     Volume: 1589 ft^3
     Surface Area Total: 822 ft^2
     Surface Area Floor: 158 ft^2
     Surface Area Ceiling+Floor: 316 ft^2
     Surface Area Front Wall: 114 ft^2
     Surface Area Front and Rear Wall: 228 ft^2
     Surface Area Left Wall: 139 ft^2
     Surface Area Left and Right Wall: 278 ft^2
     Surface Area 4 Walls: 506 ft^2
     Surface Area 4 Walls + floor: 664 ft^2




Absorbtion Coefficients

A "Sabin" is a unit of absorbtion. By definition it's the amount of sound loss in a room equivilent to an open window of size 1'x1'.
One might think that an open window represents 100% absorbtion, but it's more complicated than that. And it's possible to have more than 1 sabin of absorbtion per one square foot of material. Usually a 'sabin' is expressed for a particular frequency (band).

Doubling the frequency is a change of one octave.
Octave Band Frequencies in hz
31631252505001k2k4k8k16k
1/3 Octave Band Frequencies in hz
31405063801001251602002503154005006308001k1.2k1.6k2k2.5k3.2k4k5k6.3k8k10k12k16k
"The absorption coefficient is the absorption per covered unit of floor surface (or whatever boundary)." (quote from Eric Desart).
has units of "Sabins / ft^2".

is different for different objects/materials, and different mountings/placement, and at different frequencies.
Absorbtion Coefficients, while resembling percentages, are not percentages. They are not transferable between mountings/placement methods. For a given frequency, and a given mounting/placement, an absorbtion coefficient is a multiplier for use in the Sabine Equation.

Here's a chart of values for some things one might find in a home theater:
Material125 hz250 hz500 hz1000 hz2000 hz4000 hz
Carpet0.080.240.570.690.710.73
Drywall wall 2 layer 5/8"0.100.080.050.030.030.03
Drywall wall 1 layer 5/8"0.150.080.050.030.030.03
6" of 703 on wall1.191.211.131.051.041.04
Studiotips Superchunk1.841.761.651.401.311.30
Leather Recliner (each, not per ft^2)3.003.753.503.002.502.00
Theater upholstered chair (each, not per ft^2)1.503.404.004.504.754.50

You can certainly see that different materials absorb differently at different frequencies from the above chart.

For more common materials please see: Studiotips Sabin Data (absorbtion coefficients for many things) (data from 63hz to 8khz)
For even more materials please see: Bob Golds Sabin Data (absorbtion coefficients for other things)
For DIY absorber components please see: Bob Golds Fiberglass/Rockwool Absorbtion Coefficients page

Absorbtion coefficents, averaged to the octave bands, do not nessessarily tell the whole story. A porous absorber may have an absorbtion curve like this.


A microperforated panel absorber may have an absorbtion curve like this.




Mounting and Placement

Let's talk a little bit about mounting/placement's effects on

When a product is tested in a laboritory, it's often done to a standard such as ASTM C423 & E795 (Mounting), which gives values for: Absorption Coefficients (one for each of the six frequency bands: 125hz, 250hz, 500hz, 1000hz, 2000hz, and 4000hz), Reverberation Times (T60s), Sabins or Metric Sabins (1/3 octave bands, values less than 100hz are not accurate), Noise Reduction Coefficient (NRC). ATSM C423 uses a reverberation room (six reflective concrete surfaces perhaps non parallel walls and ceiling), putting 72ft^2 of the material (about 8'x8') all together in a square on the center of the floor. The measurements in the lab are dependant upon this diffuse sound field in the chamber (not direct sound). A diffuse sound field assumes that sound travels with equal probability in all directions. In a reverberation room that is true throughout the room, except over the absorber. If you build your home theatre like that (no other absorbtion in the room, lots of reflective surfaces, a single 8'x8' absorber in the middle of the floor) then the measured absorbtion coefficients will be roughly what you get. I say roughly, because there is some error/uncertainty in the laboritory testing of identical materials, and in the transerability of measurements to different materials or different rooms.

In a Dennis Erskine style theater, with the entire front wall covered in absorbtion, and the bottom half the remaining three walls, and carpet on the floor, the absorbtion coefficients for the ATSM style method may also be useable -- because the absorbtion is all together, just like it was in the lab. They may be a little high though, since the percentage of absorbed surface area is so much higher in the home theatre than the laboratory test.
i.e. these values Bob Golds Fiberglass/Rockwool Absorbtion Coefficients page would be safe to use.

#1 - When a porous material is placed further from the wall, its absorbtion changes.
Usually more absorbtion in the bass, with no change in the trebble
MaterialMounting125 hz250 hz500 hz1000 hz2000 hz4000 hz
701, plain 2" thickon wall0.220.670.981.020.981.00
701, plain 2" thickwith 16" air between 701 and wall0.761.020.981.071.041.20

#2 - When a porous material is placed near a corner, its absorbtion changes.
Usually more absorbtion in the bass and apparently some in the trebble
The first one below is done with a 72ft^2 sample, whereas the Studiotips Corner Chunk is done with a 2'x4'x4" piece (8 ft^2 sample).
MaterialMounting125 hz250 hz500 hz1000 hz2000 hz4000 hz
703, plain 4" thickon wall0.841.241.241.081.000.97
703, plain 4" thick2'x8' mounted 30" diagonally across a corner
Studiotips Corner Absorber		1.851.942.071.751.601.56
This is important. Some of the absorbtion boost in the bass of the Studiotips Corner Absorber is due to diffusion effects that extend outside the surface area of the absorber. So if you put absorbtion on the walls on both sides of the Studiotips Corner Absorber then the absorbtion of the Studiotips Corner Absorber will probably drop. Again the absorbtion coefficents correspond to EXACTLY how the lab measured it. If you deviate from the method of placement that the lab used, and what they put around it (other absorbers, frames), the absorbtion coefficients will change.

Note, one should use Sabins Per Lineal Foot Of Corner, rather than absorbtion coefficients per square foot that I calculated for the example above, when dealing with Corner absorbers. Most absorbtion coefficients are per square foot. The ones from studiotips corner chunks are per linear foot. If your room is 7.5 tall, then you'll need 7.5 linear feet, so multiply the numbers from studiotips by 7.5. If you room is 12' tall, then you'll need 12 linear feet, so multiply the numbers from studiotips by 12. In otherwords it's a one dimensional coefficient, the height of the absorber. So you sort of ignore the diagonal surface 2D area, because it's already there in the coefficient.


#3 - When a porous material is separated, such as in a checkerboard pattern, its absorbtion changes.
Usually more absorbtion in the bass, with little change in the trebble
"The discontinuity in the wave field at the edge of the specimen create a diffraction effect that warps the sound field to make the specimen appear as much as a quarter-wavelength larger in each direction." (from Proceedings of Noise Con 90, David A. Nelson, P.E., INCE Bd. Cert., "Diffraction Effect" in Sound Absorption Tests: Why is the sound absorption coefficient greater than 1.00?)

In the below example, the absorbers have frames around the sides. So this boost in absorbtion, primarily in the bass, is due to edge/diffraction effects, and not due to any increase in surface area of the porous part of the absorber such as hieght of the sides. All he did was spread them out.


In the below mounting, the absorbers have been spaced into a checkerboard pattern.
click to see a bigger image
Lab reports that there are 25 sabins at 250hz for pattern/distribution/density A, mounted flush on the floor.
Lab reports that there are 15 sabins at 250hz for pattern/distribution/density B, mounted flush on the floor. Notice how even though we have half the absorber material, we have more than half the absorbtion at this frequency.
Lab reports that there are 30 sabins at 250hz for pattern/distribution/density C, mounted flush on the floor. Notice how even though we the same absorber material, we have more than the original absorbtion at this frequency.

This should be obvious by now, but if a company publishes absorbtion coefficients, but doesn't specify EXACTLY how the test was conducted, then the published absorbtion coefficients are COMPLETELY USELESS TO EVERYONE. It would be best if companies tested and published two sets of absorbtion coefficients
a) ASTM C423 style (with the 8'x8' bunched together on the floor -- not raised up)
b) How they are likely to be used (e.g. mounted diagonally on corners, first reflection points)
That way people can compare the product from vendor to vendor via (a), and do RT60 calcs with (b). Oh life would be grand.

Similarly if someone publishes absorbtion coefficients for ONE chair in a reverb chamber, then they are not transferable to an ARRAY of chairs.

For more details on this topic, please see read:
a) Studiotips thread: Absorbtion coefficient question
b) Edge/Diffraction Effect by Eric Desart
c) Playing With Baffels by Eric Desart



RT60 Calculation


I'll start by doing some very trivial manipulation of the Sabine Equation. Not because it's required, but just to get a better feel of what we're multiplying.
Here it is the same as above:

where:
  RT60 = reverberation time, in seconds
  V = volume of room, in cubic feet (ft^3)
  S = surface area, in square feet (ft^2)
  = average absorbtion coefficient

Absorbtion Coefficients have units of "Sabins / ft^2".



The above Sabins is for the whole room, and it is the sum of the sabins for each of the components of the room. So it could be written as

where Sabinsi is the Sabins absorbed by each individual thing in the room: a wall, a chair, a carpet, etc.
  Sabins1 = the absorbtion of the wall
  Sabins2 = the absorbtion of a chair
  Sabins3 = the absorbtion of the carpet

Substituting the Surface Area (S) and Absorbion Coefficient () back into the equation we have

  RT60 = reverberation time, in seconds
  V = volume of room, in cubic feet (ft^3)
  Si = surface area, in square feet (ft^2), of each individual object
  i= absorbtion coefficient, of each individual object

We saw above that is frequency dependant.
Material125 hz250 hz500 hz1000 hz2000 hz4000 hz
Carpet0.080.240.570.690.710.73
6" of 703 on wall1.191.211.131.051.041.04

So if f is frequency then we have

Substituting the six Octave Band Frequencies into that gives







Lets say that in our room of Length=13.92 ft, Width=11.42 ft, Height=10 ft,
  Volume: 1589 ft^3
  Surface Area 4 Walls + ceiling: 664 ft^2
  Surface Area Floor: 158 ft^2
that we have carpet and nothing else (no walls?!).
We'll use the above absorbtion coefficients for it. (Different carpet, with different padding, has different )

Material125 hz250 hz500 hz1000 hz2000 hz4000 hz
Carpet0.080.240.570.690.710.73

Sabinscarpet @ f= Scarpet * carpet @ f

Sabinscarpet @ 125hz= (158 ft^2) * (0.08 Sabins / ft^2)
= 12.64 Sabins

Sabinscarpet @ 250hz= (158 ft^2) * (0.24 Sabins / ft^2)
= 37.92 Sabins

Sabinscarpet @ 500hz= (158 ft^2) * (0.57 Sabins / ft^2)
= 90.06 Sabins

Sabinscarpet @ 1000hz= (158 ft^2) * (0.69 Sabins / ft^2)
= 109.02 Sabins

Sabinscarpet @ 2000hz= (158 ft^2) * (0.71 Sabins / ft^2)
= 112.18 Sabins

Sabinscarpet @ 4000hz= (158 ft^2) * (0.73 Sabins / ft^2)
= 115.34 Sabins

We can feed those results back into the Sabine Equation

RT60carpet @ 125hz= (0.049) * (1589 ft^3) / (12.64 Sabins)
= 6.15 seconds

RT60carpet @ 250hz= (0.049) * (1589 ft^3) / (37.92 Sabins)
= 2.05 seconds

RT60carpet @ 500hz= (0.049) * (1589 ft^3) / (90.06 Sabins)
= 0.86 seconds

RT60carpet @ 1000hz= (0.049) * (1589 ft^3) / (109.02 Sabins)
= 0.71 seconds

RT60carpet @ 2000hz= (0.049) * (1589 ft^3) / (112.18 Sabins)
= 0.69 seconds

RT60carpet @ 4000hz= (0.049) * (1589 ft^3) / (115.34 Sabins)
= 0.67 seconds

RT60 is inversely proportional to Total Sabins. I'll graph Total Sabins.
Obviously this isn't a flat curve, so neither is the RT60


Let's do the same for the walls and ceiling. We'll assume that the ceiling has the same as the walls.

Material125 hz250 hz500 hz1000 hz2000 hz4000 hz
Drywall wall 2 layer 5/8"0.100.080.050.030.030.03

Sabinswalls @ f= Swalls * walls @ f

Sabinswalls @ 125hz= (664 ft^2) * (0.10 Sabins / ft^2)
= 66.4 Sabins

Sabinswalls @ 250hz= (664 ft^2) * (0.08 Sabins / ft^2)
= 53.12 Sabins

Sabinswalls @ 500hz= (664 ft^2) * (0.05 Sabins / ft^2)
= 33.2 Sabins

Sabinswalls @ 1000hz= (664 ft^2) * (0.03 Sabins / ft^2)
= 19.92 Sabins

Sabinswalls @ 2000hz= (664 ft^2) * (0.03 Sabins / ft^2)
= 19.92 Sabins

Sabinswalls @ 4000hz= (664 ft^2) * (0.03 Sabins / ft^2)
= 19.92 Sabins

We can feed those results back into the Sabine Equation, including the results for both the carpet and the walls

RT60@ 125hz= (0.049) * (1589 ft^3) / (12.64 + 66.4 Sabins)
= (0.049) * (1589 ft^3) / (79.04 Sabins)
= 0.98 seconds

RT60@ 250hz= (0.049) * (1589 ft^3) / (37.92 + 53.12 Sabins)
= (0.049) * (1589 ft^3) / (91.04 Sabins)
= 0.85 seconds

RT60@ 500hz= (0.049) * (1589 ft^3) / (90.06 + 33.2 Sabins)
= (0.049) * (1589 ft^3) / (123.26 Sabins)
= 0.63 seconds

RT60@ 1000hz= (0.049) * (1589 ft^3) / (109.02 + 19.92 Sabins)
= (0.049) * (1589 ft^3) / (128.94 Sabins)
= 0.60 seconds

RT60@ 2000hz= (0.049) * (1589 ft^3) / (112.18 + 19.92 Sabins)
= (0.049) * (1589 ft^3) / (132.1 Sabins)
= 0.58 seconds

RT60@ 4000hz= (0.049) * (1589 ft^3) / (115.34 + 19.92 Sabins)
= (0.049) * (1589 ft^3) / (135.26 Sabins)
= 0.57 seconds

This is a little flatter. The walls absorb at the low frequencies that the carpet does not.



ContraCarpet is nickname for a DIY a perforated helmholtz resonator, 2" deep, with 3/16" holes on 6" centers in 3/16" plywood, with 2" of 703 inside.
We'll let it cover 56 ft^2 on the ceiling.

Material125 hz250 hz500 hz1000 hz2000 hz4000 hz
ContraCarpet0.900.540.300.160.120.10

SabinsContraCarpet @ f= SContraCarpet * ContraCarpet @ f

SabinsContraCarpet @ 125hz= (56 ft^2) * (0.90 Sabins / ft^2)
= 50.4 Sabins

SabinsContraCarpet @ 250hz= (56 ft^2) * (0.54 Sabins / ft^2)
= 30.24 Sabins

SabinsContraCarpet @ 500hz= (56 ft^2) * (0.30 Sabins / ft^2)
= 16.8 Sabins

SabinsContraCarpet @ 1000hz= (56 ft^2) * (0.16 Sabins / ft^2)
= 8.96 Sabins

SabinsContraCarpet @ 2000hz= (56 ft^2) * (0.12 Sabins / ft^2)
= 6.72 Sabins

SabinsContraCarpet @ 4000hz= (56 ft^2) * (0.10 Sabins / ft^2)
= 5.6 Sabins

We can feed those results back into the Sabine Equation

RT60@ 125hz= (0.049) * (1589 ft^3) / (12.64 + 66.4 + 50.4 Sabins)
= (0.049) * (1589 ft^3) / (129.44 Sabins)
= 0.60 seconds

RT60@ 250hz= (0.049) * (1589 ft^3) / (37.92 + 53.12 + 30.24 Sabins)
= (0.049) * (1589 ft^3) / (121.28 Sabins)
= 0.64 seconds

RT60@ 500hz= (0.049) * (1589 ft^3) / (90.06 + 33.2 + 16.8 Sabins)
= (0.049) * (1589 ft^3) / (140.06 Sabins)
= 0.55 seconds

RT60@ 1000hz= (0.049) * (1589 ft^3) / (109.02 + 19.92 + 8.96 Sabins)
= (0.049) * (1589 ft^3) / (137.9 Sabins)
= 0.56 seconds

RT60@ 2000hz= (0.049) * (1589 ft^3) / (112.18 + 19.92 + 6.72 Sabins)
= (0.049) * (1589 ft^3) / (138.82 Sabins)
= 0.56 seconds

RT60@ 4000hz= (0.049) * (1589 ft^3) / (115.34 + 19.92 + 5.6 Sabins)
= (0.049) * (1589 ft^3) / (140.86 Sabins)
= 0.55 seconds

This is even flatter.




RT60 Calculation Spreadsheet

Nobody in their right mind does all these computations by hand as I've just shown.
Any sane person would create an excel spreadsheet to do all that work, and it looks like this (Wideband is 4" of 703):


Here is that Excel Spreadsheet for you to use
You can insert a row to add a material, or change absorbtion coefficients, or change surface area and room size, to suit any room.

Combined with these links (same as above), you should be able to do any RT60 calculation:
  For more common materials please see: Studiotips Sabin Data (absorbtion coefficients for many things) (data from 63hz to 8khz)
  For even more materials please see: Bob Golds Sabin Data (absorbtion coefficients for other things)
  For DIY absorber components please see: Bob Golds Fiberglass/Rockwool Absorbtion Coefficients page






Recommended Reverberation Time


You may ask, how much absorbtion should I put into my home theatre?
Or, what RT60 should I have in my home theatre

Since RT60 is a function of room absorbtion, they are both the same question.

There's some debate about the recommended RT60 for a home theatre.
Some recommend that it should be very dead indeed (deader than ITU below), particularly for rooms smaller than 1500ft^3, with lots of thick absorbtion, and very few paths for an untrapped reflection.
Some recommend that the RT60 doesn't have to be flat, that longer RT60's in the 125hz and 250hz are just fine. For several views on the non-flat RT60, please see http://www.aes.org/technical/documents/AESTD1001.pdf

The best advice I know of today (subject to change) to follow the ITU Control Room Recommended RT60.

The ITU RT60 specification for rooms < 12,000 cu. ft is specified in the form:
  Control Room Recommended RT60 = 0.3 *{(volume cu ft / 3531.34 cu ft) raised to 1/3 power}
  Control Room Recommended RT60 = 0.25 * (( ProposedRoomVolume / 100 m^3 ) ^ .3333)
  (1 cubic foot = 0.0283168 cubic meter)

That means that RT60 is simply a function of volume (which we know). And then total room absorbtion in sabins is a function of RT60.
To see some sample values of the ITU RT60, please click here

But to save you time calculating, just type your room dimensions into Room Modes Calculator and it will show you 
     Room Dimensions: Length=13.92 ft, Width=11.42 ft, Height=10 ft
     Volume: 1589 ft^3
     RT60 (ITU Control Room Recommended): 191 ms
     Absorbtion to achieve RT60: 406 sabins
'ms' is milli-seconds, or thousands of a second.



Appendix


V in ft^3V in m^3ITU RT60
631.80.07(shower stall - waterproof acoustical treatment required?)
100028.30.16
125035.40.18
150042.50.19
175049.60.20(approximately 16' x 16' x 7')
200056.60.21
225063.70.22
250070.80.22
275077.90.23
300085.00.24
325092.00.24
350099.10.25
3750106.20.26
4000113.30.26
4250120.30.27
4500127.40.27
4750134.50.28
5000141.60.28
5250148.70.29
5500155.70.29
5750162.80.29
6000169.90.30
6250177.00.30
6500184.10.31
6750191.10.31
7000198.20.31
7250205.30.32
7500212.40.32
7750219.50.32
8000226.50.33
8250233.60.33
8500240.70.34
8750247.80.34
9000254.90.34
9250261.90.34
9500269.00.35
9750276.10.35
10000283.20.35
11000311.50.37
12000339.80.38
13000368.10.39
14000396.40.40
15000424.80.40
16000453.10.41
17000481.40.42
18000509.70.43
19000538.00.44
20000566.30.45
22500637.10.46
25000707.90.48
27500778.70.50
30000849.50.51
32500920.30.52
35000991.10.54
375001061.90.55
400001132.70.56
500001415.80.60
600001699.00.64
700001982.20.68
800002265.30.71
900002548.50.74
1000002831.70.76
1250003539.60.82
1500004247.50.87
1750004955.40.92
2000005663.40.96
2250006371.31.00(approximately 100' x 100' x 22')



DecibelRelative EnergyAbsorbtionWatts/m^2Example
-10 dB0.101.0E-13
-5 dB0.323.2E-13
0 dB1.000.001.0E-12Threshold of Hearing
1 dB1.260.211.3E-12
2 dB1.580.371.6E-12
3 dB2.000.502.0E-12
4 dB2.510.602.5E-12
5 dB3.160.683.2E-12
6 dB3.980.754.0E-12
7 dB5.010.805.0E-12
8 dB6.310.846.3E-12
9 dB7.940.877.9E-12
10 dB10.00.901.0E-11soft rustling Leaves
11 dB12.60.921.3E-11
12 dB15.80.941.6E-11
13 dB200.952.0E-11
14 dB250.962.5E-11
15 dB310.973.2E-11
16 dB390.974.0E-11
17 dB500.985.0E-11
18 dB630.986.3E-11
19 dB790.997.9E-11
20 dB1000.991.0E-10Whisper, very quiet room
30 dB10001.001.0E-09
40 dB10,0001.001.0E-08library, quiet residential area
50 dB100,0001.001.0E-07Regrigerator, large office
60 dB1,000,0001.001.0E-06Normal conversation, washing machine
70 dB10,000,0001.001.0E-05Busy Street, television
75 dB31,622,7771.003.2E-05alarm clock, average city street
80 dB100,000,0001.001.0E-04Vacuum Cleaner, doorbell, telephone, moderate stereo
85 dB316,227,7661.003.2E-04food mixer, heavy traffic
90 dB1,000,000,0001.001.0E-03tractor, electric drill, shout, loud stereo
100 dB10,000,000,0001.001.0E-02Orchestra, Walkman at max, factory machinery, motorcycle
110 dB100,000,000,0001.001.0E-01disco, baby crying, leafblower, car horn
120 dB1,000,000,000,0001.001.0E+00chain saw, jet plane, ambulance siren, rock concert, pain
130 dB10,000,000,000,0001.001.0E+01jackhamer
140 dB100,000,000,000,0001.001.0E+02Jet aircraft
150 dB1,000,000,000,000,0001.001.0E+03baloon pop
160 dB10,000,000,000,000,0001.001.0E+04Perforation of Eardrum, gun, fireworks at 3 feet
170 dB100,000,000,000,000,0001.001.0E+05shotgun
177 dB501,187,233,627,273,0001.005.0E+05record for car audio
180 dB1,000,000,000,000,000,0001.001.0E+06Apollo Rocket at pad
194 dB25,118,864,315,095,800,0001.002.5E+07Maximum possible (from atmospheric 14.7psi down to 0psi)



References:

"How to Build A Small Budget Recording Studio From Scratch : With 12 Tested Designs "
by Michael Shea and F. Alton Everest
Publisher: McGraw-Hill/TAB Electronics; 3 edition (May 29, 2002)
ISBN: 0071387005
Note: This is perhaps the best book on RT60 I've ever seen

"Master Handbook of Acoustics, Fourth Edition"
by F. Alton Everest
Publisher: McGraw-Hill/TAB Electronics; 4 edition (September 22, 2000)
ISBN: 0071360972

"Recording Studio Design, First Edition"
by Phillip Newell
Publisher: Focal Press; 1 edition (March 18, 2003)
ISBN: 0240519175

"Building a Recording Studio"
by Jeff Cooper
Publisher: Synergy Group; 4th edition (June 1, 1984)
ISBN: 0916899004

"Acoustic Absorbers and Diffusers: Theory, Design, and Application"
by Trevor J. Cox, Peter D'Antonio
Publisher: Spons Architecture Price Book (April 1, 2004)
ISBN: 0415296498

"Sabine Equation and Sound PowerCalculations"
by Young, Robert W.
Publisher: J. Accous. Soc. Am. 31, 12 (1959, 1681)

Studiotips Superchunk
Studiotips Corner Absorber
Studiotips Corner Absorption Comparision test
by Eric Desart and Jeff D. Szymanski
normalized sabins per square foot of corner


Edge/Diffraction Effect

source of above image
by Eric Desart and Cath. Univ. Leuven/Belgium

Playing With Baffles

source of above image
by Eric Desart

Chris Whealy's Porous Absorber Calculator V1.5

Bob Golds Fiberglass/Rockwool Absorbtion Coefficients page

Bob Golds Sabin Data (absorbtion coefficients for other things)

RPG Graphs SBIR, Modal Coupling, Comb Filtering, Wall Reflections, Speaker Positioning

RPG D'Antonio: Listen to the Music, Not the Room. Lists causes of acoustic distortion: Modal, SBIR, Comb, Diffusion and room treatment summary.

RPG Types of Diffusers