STC vs FSTC
John The Depot Dude home theatre walls, May 16 2004
Isolation description/construction (Walls, Ceiling, Floor, Doors, HVAC, electrical)
HVAC - noise upstairs is clear due to nothing in the straight rectangular ducts
Door - french doors, with overlap (i.e. one layer of solid core door)
Walls - 1/2" drywall, 5/8 drywall, Sonopan Sound board, 2x6 (not staggered) with fluffy yellow insulation, Sonopan Sound board, 5/8 drywall, 1/2" drywall.
Ceiling - 1/2" drywall, 5/8 drywall, Sonopan Sound board, 2x10 with fluffy yellow insulation, plywood, ceramic tile
Notes
The room has equipment (amplifiers, scaler, DVD player, etc) mounted in a hole in the wall. The hole is 4' tall and 5' wide with non air tight glass doors that are often left open. The back of this equipment area is under untreated stairs, and has a hollow core door over carpet with a 1/4" gap under the door and above the carpet.
insul48SA.exe prediction
Assuming: 1/2" drywall, 5/8 drywall, 2x6 with insulation, 5/8 drywall, 1/2" drywall.
STC-48, 49hz mass-air-mass resonance
50 hz 20db TL
63 hz 23db TL
125 hz 34db TL
250 hz 41db TL
500 hz 46db TL
1k hz 50db TL
2k hz 48db TL
4k hz 50db TL
Measurements
Taken with a Radio Shack Digital Sound Level Meter set to C-slow. This meter can measure from 50db to 129db.
In the HT we stood in the middle of the room to take the readings (actually about 1/2 front to back, and 1/3 width, plus or minus 4'). Outside the room we stood about 4' away from the wall to take readings
Sound source was Alan Parsons Sound Check 2 Audio Test and Demonstration CD which includes various test tones from 20hz to 20khz (not swept) that are pink noise through a narrow band filter (not a single tone, but a lot louder at that frequency with a much much less to either side). These tones were played as loud as the system could play them, although we turned down the volume at 250hz to get it to 100db and 20hz because of some speaker crackle.
The amplifiers were McIntosh, and the speakers were six B&W Nautilus 802's and Wilson Watt Puppy 7's.
The room has 1" linacoustic on the bottom 4' of all four walls.
| Frequency (hz) |
HT source db |
4' Outside of Door db |
Door TL |
4' other side of wall db |
Wall TL |
Upstairs db |
Ceiling TL |
| 20 |
90 |
70 |
20 |
69 |
21 |
60 |
30 |
| 31.5 |
95 |
95 |
0 |
74 |
21 |
66 |
29 |
| 50 |
95 |
85 |
10 |
68 |
27 |
63 |
32 |
| 80 |
95 |
85 |
10 |
72 |
23 |
66 |
29 |
| 125 |
93 |
81 |
12 |
66 |
27 |
64 |
31 |
| 250 |
100 |
80 |
20 |
56 |
44 |
57 |
43 |
| 500 |
92 |
71 |
21 |
50 |
42 |
50 |
45 |
| 1000 |
90 |
64 |
26 |
heard, but < 50db |
|
heard |
|
| 2000 |
92 |
70 |
22 |
heard |
|
heard |
|
| 4000 |
97 |
73 |
24 |
heard |
|
heard |
|