DEFINITIONS OF TERMS USED IN COMPUTER PROGRAMS.
a Absorption coefficient of materials. Listed as the amount of sound
absorbed at frequencies from 125 Hz to 4KHz and ranging from .002 (2%)
to 1 Sabin per square foot.
Airloss The frequency at which the absorption of the room's air equals
it's surface absorption, the room becomes muddy, and loudspeakers must be
boosted to compensate.
ALcons(ALs) Articulation Loss, Consonants. Given as percentage of top end
loss. For best quality speech, 10%, with 15% maximum; for music, 5% and a
10% maximum.
Db SPL Sound Pressure Level, in (power formula) decibels. Three Db is
twice the power, ten Db is ten times the power and twice the loudness. 6
Db, 4x PWR, 20 Db, 100x PWR.
Dc Critical distance.The point at which the reverberant sound of a room
equals the source sound driving it and sound level becomes nearly constant.
(Echo=Source) Measured at the 3Db point.
Dl 3.16 x the Dc, the last 3Db of Dc power loss.D1 does not show as a
program listing, nor is it apparent to the ear, but is used in the program
as it is important to power calculations as power requirements double at
that distance.
Dx Distance from sound source (loudspeaker) to furthest listener.
Speaker throw.
EAD Equivalent Acoustic Distance. Apparent listener distance from source.
Ln(1-a) Conversion from standard Sabins, in which construction materials
are specified, to Norris-Eyring Sabins in which 1 Sabin per Sq Ft yields
total absorption of sound. Always used, and critical in rooms with high
percentages of absorption. Shortens RT-60, raising Dc, amplifier power
and isolation figures while lowering AlCons. Output is listed as NERT,
a shorter echo time.
NAG Needed Acoustic Gain: To produce X Db SPL at X feet of loudspeaker
throw from Y Db SPL at Z feet from the microphone.
PAG Potential Acoustic Gain. An isolation figure, mike to loudspeaker.
Usually the acoustic feedback figure for a mike-speaker system.If NAG is
6Db less than PAG no feedback will occur.
PWR T his program arbitrarily multiplies the calculated amplifier power by
10 to allow for transient peaks not read by standard VU meters, which have
a .2" rise time. A close miked piano, for instance, peaks at 30 times meter
reading, but 10 is a reasonable compromise.A high quality compressor at 3:1
will reduce 10:1 peaks to 3:1 to help prevent amplifier clipping. Properly
used, 4:1 is undetectable on voice, but can be heard on music. For general
work, compression at 2.5:1 will reduce the peak power margin to 4:1, and
is undetectable with true RMS detector units.
Q The directivity of a source. Voice is 2.5, cone speakers when ceiling
mounted about 4, (2 if free-hung) most brass instruments and common speaker
horns about 10. Specified for high quality speaker horns; maximum Q
available about 50, minimum 8. Dome tweeters have a Q of 2.8
RT60 Reverberation time decay to 60Db below starting level.Echo time in
seconds.
SEN Loudspeaker sensitivity. Specified as Db SPL at one meter or at four
feet (about 2 Db less) for one watt of amplifier power.
SPL Used in program as desired Db/SPL at furthest listener's ears.
VOLUME, As in"Turn up the volume". Level as heard by the human ear.
Not used in the program as such, but it is essential to know that to
double the perceived volume, one must increase power by 10. Twice as
loud, ten time the watts, one Bel.
RELATIONSHIPS IN ACOUSTICS: CAUSES AND EFFECTS
CAUSES; THE THINGS YOU CAN CHANGE.
1: Room size. Bigger is generally better, and much easier.
2: Sabins. The amount and kind of absorptive material in the room.
3: Source (usually loudspeaker) Q. The beam width/height of the sound source.
4: Loudspeaker Sound Pressure Level. Affects listeners, but not acoustics.
EFFECTS; HOW CAUSES CHANGE WHAT IS HEARD IN THE ROOM.
The relationships take four forms. 1: DIRECT; More x, more y. 2: INVERSE;
More x, less y. 3: SQUARE; Double x, multiply y by 1.414, halve x, divide
y by 1.414 (or multiply by .707). LOGARITHMIC; small changes in x yield
small changes in y, large changes in x yield enormous changes in y.
1: RT-60 to Sabins. RT-60 is room echo time. Depends on the amount of
absorption in the room, and is an INVERSELY LOGARITHMIC relationship.
Doubling the amount of physical Sabins in a room will reduce room time
by more than half. Often much more. See NORRIS-EYRING elsewhere.
2: RT-60 to Critical Distance (Dc). Dc is the distance at which the level
of a sound source becomes constant in a room. The relationship is INVERSLY
SQUARE. Double the RT, Dc multiplies by .707, Halve the RT, Dc multiplies
by 1.414, BUT Dc is also an absolute function of Sabins in that x Sabins
will yield y Dc in a room regardless of the RT produced by the Sabins.
3: Sabins to Acoustical Loss of Consonants (AlCons). AlCons, expressed as
a percentage at a given distance, amount to clarity of sound. The
relationship is simply INVERSE to effective Sabins. Double the Sabins,
double the distance for a given percentage of AlCons.
4: Source Q to Dc. DIRECTLY SQUARE relationship. Double the Q, Dc
multiplies by 1.414
5: Source Q to AlCons. INVERSLY SQUARE relationship. Double the Q, AlCons
multiply by .707
6: Room size to Sabins/RT. Simple DIRECT relationship. Double the room
VOLUME, double the time given the same number of effective Sabins.
7: Sound Pressure Levels, which involve room losses, loudness and source
power will be dealt with elsewhere, as they are too complex to detail here.
MATERIAL SABINS/Sq FOOT AT (Hz) 125 250 500 1k 2k 4k
ACOUSTIC TILE, GLUED ON 0.20 0.35 0.60 0.70 0.80 0.75
ACOUSTIC TILE, SUSPENDED 0.40 0.50 0.65 0.70 0.80 0.75
BRICK, UNGLAZED 0.03 0.03 0.03 0.04 0.05 0.07
BRICK, UNGLAZED, PAINTED 0.01 0.01 0.02 0.02 0.02 0.03
CARPET, 1/8 INCH, NO PAD 0.05 0.05 0.10 0.20 0.30 0.40
CARPET, 1/4 INCH, NO PAD 0.05 0.10 0.15 0.30 0.50 0.55
CARPET, 3/16 COMBINED PILE & FOAM 0.05 0.10 0.10 0.30 0.40 0.50
CARPET, 5/16 COMBINED PILE & FOAM 0.05 0.15 0.30 0.40 0.50 0.60
CINDER BLOCK, UNPAINTED 0.36 0.44 0.31 0.29 0.29 0.25
CINDER BLOCK, PAINTED 0.10 0.05 0.06 0.07 0.09 0.08
CONCRETE/MARBLE FLOORS 0.01 0.01 0.01 0.02 0.02 0.02
CONCRETE/STONE WALLS 0.02 0.02 0.02 0.03 0.04 0.04
FIBERGLAS, UNFACED, 3 1/2 IN ON WALL 0.34 0.85 1.09 0.97 0.97 1.12
FIBERGLAS, UNFACED, 6 1/4 IN ON WALL 0.64 1.14 1.09 0.99 1.00 1.21
FIBERGLAS, PAPER OUT, 6 1/4 ON WALL 0.94 1.33 1.02 0.71 0.56 0.39
FIBERGLAS, UNFACED, 12IN ON WALL 1.14 1.09 1.09 0.99 1.00 1.21
FIBERGLAS 703 BOARD, 1 IN ON WALL 0.03 0.22 0.69 0.91 0.96 0.99
FIBERGLAS 703 BOARD, 2 IN ON WALL 0.22 0.82 1.21 1.10 1.02 1.05
FIBERGLAS 703 BOARD, 3 IN ON WALL 0.53 1.19 1.21 1.08 1.01 1.04
FIBERGLAS 703 BOARD, 4 IN ON WALL 0.84 1.24 1.24 1.08 1.00 0.97
FIBERGLAS 703 BOARD, 6 IN ON WALL(est) 1.19 1.21 1.13 1.05 1.04 1.04
FIBERGLAS GRID CEILING, 1 1/2 INCH 0.97 1.00 0.86 1.01 1.04 1.06
GLASS, 1/8 INCH 0.35 0.25 0.18 0.12 0.07 0.04
GLASS, 1/4 INCH 0.10 0.06 0.04 0.03 0.02 0.02
GYPSUM BOARD, 1/2 INCH 0.29 0.10 0.05 0.04 0.07 0.04
LINOLEUM, ASPHALT FLOOR TILE, ETC. 0.02 0.03 0.03 0.03 0.03 0.02
MARBLE/GLAZED TILE 0.01 0.01 0.01 0.01 0.02 0.02
HEAVILY UPHOLTERED SEATS, EACH 3.54 0.55 0.05 0.55 0.54 0.50
PEOPLE IN UPHOLSTERED SEATS, EACH 2.53 0.54 0.04 0.55 0.04 0.50
PEOPLE IN PADDED SEATS, EACH 4.05 0.05 0.56 0.57 0.07 0.00
PLASTER OVER MASONRY 0.013 .015 .02 0.03 0.04 0.05
PLASTER ON LATHING 0.02 0.02 0.03 0.04 0.04 0.03
SONEX, 2 INCH 0.08 0.25 0.61 0.92 0.95 0.92
SONEX, 3 INCH 0.14 0.43 0.98 1.03 1.00 1.00
SONEX, 4 INCH 0.20 0.70 1.06 1.01 1.01 1.00
TECTUM GRID CEILING, 1 INCH 0.40 0.42 0.35 0.48 0.60 0.93
ABOVE WITH 6 INCH FIBERGLAS OVERLAY 1.01 0.89 1.06 0.97 0.93 1.13
TECTUM ON WALL, 1 INCH 0.06 0.13 0.24 0.45 0.82 0.64
TECTUM ON WALL, 2 INCH 0.15 0.26 0.62 0.94 0.64 0.92
TECTUM 32 X 3 INCH BLOCKS PER UNIT 0.45 0.71 1.87 2.94 2.90 2.91
VELOUR, LIGHT, HUNG STRAIGHT ON WALL 0.03 0.04 0.11 0.17 0.24 0.35
VELOUR, MEDIUM, DRAPED TO HALF AREA 0.07 0.31 0.49 0.75 0.70 0.60
VELOUR, HEAVY, AS ABOVE 0.14 0.35 0.56 0.72 0.70 0.65
WATER, SURFACE .008 .008 .013 .015 .020 .025
WOOD FLOORING 0.15 0.11 0.10 0.07 0.06 0.07
WOOD PARQUET IN ASPHALT ON CONCRETE 0.04 0.04 0.07 0.06 0.06 0.07
WOOD PANELING OVER 2-4 INCH AIR SPACE 0.30 0.25 0.20 0.17 0.15 0.10
WOOD DECK, UNSEALED TONGUE & GROOVE 0.24 0.19 0.14 0.08 0.10 0.15
SOUND TRANSMISSION LOSS IN Db SPL. 125 250 500 1K 2K 4K
BRICKWORK, PLASTERED 4 3/8 INCH 31 36 41 50 55 61
BRICKWORK, PLASTERED 8 3/4 INCH 41 45 50 56 63 62
CONCRETE BLOCK, LIGHT, 12 INCH 38 44 49 54 58 62
REINFORCED CONCRETE, 4 INCH 38 44 49 54 58 62
GLASS, SINGLE STRENGTH, 3/32 INCH 13 14 21 26 32 30
GLASS, DOUBLE STRENGTH, 1/8 INCH 14 17 23 28 33 32
GLASS, PLATE, 1/4 INCH 21 24 27 31 25 32
GLASS, LAMINATED PLATE, 1/4 INCH 30 28 31 35 36 41
GLASS, PLATE, 1/2 INCH 20 28 31 27 36 44
GLASS, LAMINATED PLATE, 1/2 INCH 31 33 36 35 40 49
GLASS, 1/4 & 1/4 INCH, 6 INCH SPACE 31 37 43 48 44 56
GLASS, 1/2 & 1/4 INCH, 6 INCH SPACE 32 38 39 38 38 54
GLASS, 1/4 & 1/4 INCH, 8 INCH SPACE 40 42 49 56 43 59
GYPSUM BOARD, 1/2 INCH 17 20 23 23 23 24
GYPSUM BOARD, 5/8 INCH 19 22 25 28 22 31
PLYWOOD, 3/4 INCH 19 23 27 25 22 30
PLASTER AND LATH CEILING 22 27 31 36 34 42
WALL CONSTRUCTION FIGURES 125 250 500 1K 2K 4K
2X4X16 O.C. WOOD STUDS, 1/2 INCH WALLBOARD EACH SIDE 15 27 42 47 47 40
AS ABOVE WITH FIBERGLAS FILLING 15 31 40 46 50 42
AS ABOVE WITH DOUBLE 1/2 INCH WALLBOARD EACH SIDE 21 37 45 50 55 51
2X4X16 O.C. WOOD DOUBLE STUDS, 1/2 INCH EACH SIDE 30 41 45 50 55 49
AS ABOVE WITH FIBERGLAS FILLING 32 48 57 63 64 61
AS ABOVE WITH DOUBLE 1/2 INCH WALLBOARD EACH SIDE 36 48 59 64 66 63
2.5X24 O.C. METAL STUDS, 1/2 INCH BOARD EACH SIDE 17 24 36 45 45 41
AS ABOVE WITH FIBERGLAS FILLING 22 38 51 57 47 44
AS ABOVE WITH DOUBLE 1/2 INCH WALLBOARD EACH SIDE 36 49 60 62 64 55
3.3X24 O.C. METAL STUDS, 1/2 INCH BOARD EACH SIDE 25 28 42 49 50 40
AS ABOVE WITH FIBERGLAS FILLING 28 39 52 56 58 46
AS ABOVE WITH DOUBLE 1/2 INCH WALLBOARD EACH SIDE 39 46 55 61 63 55
IF ALL ELSE FAILS, THE MASS LAW FOR RIGID MATERIAL IS: 20X 10 LOG(HzXKg/M2)-47
LOSS IN Db SPL EQUALS 20 TIMES THE 10 LOG OF FREQUENCY IN HZ TIMES MASS IN
KILOGRAMS PER SQUARE METER, MINUS 47 Db. IF IN LB/SQ FT, MULTIPLY BY 4.89
NOTE: This is a list of typical professional loudspeakers. Not all
manufacturers, not all models, not recently updated. It is useful to
see what's generally available for early design parameters. For any
specific model, type, or manufacturer CALL THE MAKER OR DEALER.
Tannoy time aligned studio monitors.
MODEL# MAX PWR SEN Q ANGLES xOVER NOTES SIZE WEIGHT
-FSM 500w 95 6 90x90 1KHz Dbl woofer 42x29x22 198 lb.
-15X 300w 95 6 90x90 1Khz. Lo end 52hz 40x26x15 112 lb.
-15XB 300w 93 6 90x90 1Khz. Lo end 40hz 40x26x15 112 lb.
-SRM10B 150w 91 6 90x90 1.2Khz Lo end 55hz 21x15x10 40 lb.
-NFM8 100w 90 5 100x100 1.8Khz Lo end 55hz 18x12x8 25 lb.
U.R.E.I. Time aligned studio monitors.
-811C 150w 95 12 90x45 1.5Khz Lo end 70hz 21x26x19 110 lb.
-813C 150w 99 12 90x45 1.5Khz Lo end 50hz 36x31x23 198 lb.
-815C 150w 101 12 90x45 1.5Khz Lo end 40hz 32x14x21 260 lb.
Altec-Lansing small room monolithic systems: Not time aligned.
-604-16X 100w 105 18 60x40 1.5Khz Lo end 20hz 40x26x18 136 lb.
-9844-8E 60w 103 13 90x40 800hz Lo end 35hz 24x31x16 90 lb.
-A7500-8E 50w 101 13 90x40 500hz Lo end 40hz 54x30x24 174 lb.
-9849-8B 60w 95 13 90x40 1.5Khz Lo end 40hz 24x21x15 60 lb.
-937 1 50w 97 6 110x60 3 Khz Lo end 70hz 24x18x16 49 lb.
James B Lansing small room monolithis systems: Not time aligned.
-4612OK 200w 95 5 100x100 3Khz Lo end 60hz 17x22x10 45 lb.
-4671OK 200w 95 13 90x40 800hz Lo end 40hz 31x22x18 113 lb.
Music quality loudspeaker components for large rooms.
Altec Lansing woofers
-8124 500w 92 2 1-12" Lo end 40hz 30x19x15 61 lb.
-8154 500w 93 2 1-15" Lo end 40hz 36x30x15 90 lb.
-8184 600w 97 2 1-18 Lo end 40hz 36x30x26 124 lb.
-8256 500w 100 3* 2-15" Lo end 65hz 36x30x15 106 lb.
-817A 150w 108 3* 2-I5" Horn load Lo end 60hz 34x38x27 224 lb.
-210 150w 108 3* 2-15" Horn load Lo end 50hz 34x84x40 386 lb.
James B Lansing woofers
-4646 300w 94 2 1-12' Lo end 65hz 16x19x11 40 lb
-4647 400w 95 2 1-15" Lo end 35hz 31x22x18 80 lb.
-4648 800w 98 3* 2-15" Lo end 35hz 42x27x18 109 lb.
-4560BKA 300w 101 2 1-15" Horn load Lo end 45hz 36x30x24 137 lb.
-4550BKA 600w 104 3* 2-15" Horn load Lo end 40hz 36x60x33 241 lb.
Altec Lansing horns.
With #290 100w 8Khz driver. Others available from Altec.
MODEL# MAX PWR SEN Q ANGLES xOVER NOTES SIZE WEIGHT
-MR-64 A 100w 112 18 60x40 500hz 1.4" Dvr 29x21x28 13 lb.
-MR-94 A 100w 110 12 90x40 500hz 1.4" Dvr 35x25x28 16 lb.
-MR-542 100w 110 50 40x20 500hz 1.4" Dvr 20x15x29 12 lb.
-MR-564 100w 108 20 60x40 500hz 1.4" Dvr 13x13x13 5 lb.
-MR-594 100w 106 10 90x40 500hz 1.4" Dvr 13x23x13 5 lb.
-MR-5124 100w 105 9 120x40 500hz 1.4" Dvr 13x24x13 5 lb.
J.B.L. large horns 2445 100w driver.
-2360A 100w 111 12 90x40 500hz 2" Dvr 32x32x32 27 lb.
-2365A 100w 113 20 60x40 500hz 2" Dvr 31x31x32 25 lb.
-2366A 100w 116 46 40x20 500hz 2" Dvr 31x31x55 36 lb.
J.B.L. compact horns 2445 driver.
-2382A 100w 108 8 120x40 500hz 2" Dvr 11x18x9 4 lb.
-2380A 100w 110 11 90x40 500hz 2" Dvr 11x18x9 6 lb.
-2370 100w 108 12 90x40 600hz 1" Dvr 7x18x7 3 lb.
-2385A 100w 112 19 60x40 500hz 2" Dvr 11x18x9 6 lb.
-2386 100w 116 45 40x20 400hz 2" Dvr 11x18x14 12 lb.