Mechanical equipment in a building in any occupancy group, when located outside of the building in a yard or court or on a roof, or where the equipment opens to the exterior of the building, shall be subject to the noise output limitations given in Table 926.1 where one or more windows of a dwelling unit in any building in occupancy groups R-1, R-2, and R-3, are located within a sphere of 100 foot radius (30 480 mm) whose center is any part of the equipment or its housing, unless it can be shown that the sound pressure levels, in octave bands, of the exterior mechanical equipment as measured within the dwelling unit do not exceed the levels given in Table 926.1(2).
| OCTAVE BANDS CENTER FREQUENCY (cps) |
DECIBELS RE .0002 MICROBAR |
|---|---|
| 63 | 61 |
| 125 | 53 |
| 250 | 46 |
| 500 | 40 |
| 1000 | 36 |
| 2000 | 34 |
| 4000 | 33 |
| 8000 | 32 |
- Measurements shall be obtained with a sound level meter and octave band analyzer, calibrated both electronically and acoustically before and after the measurements are made.
| MAXIMUM SOUND POWER LEVELS IN OCTAVE BANDS – db re 10-13 WATTSa | ||||||||
|---|---|---|---|---|---|---|---|---|
| MINIMUM DISTANCE FROM EQUIPMENT TO EXTERIOR WINDOW (ft.)a |
Octave Bands c.p.s. Mid Frequency | |||||||
| 63 | 125 | 250 | 500 | 1000 | 2000 | 4000 | 8000 | |
| 12 | 97 | 90 | 83 | 78 | 75 | 73 | 72 | 71 |
| 25 | 104 | 96 | 89 | 84 | 81 | 79 | 78 | 77 |
| 50 | 110 | 102 | 95 | 90 | 87 | 85 | 84 | 83 |
| 100 | 116 | 108 | 101 | 96 | 93 | 91 | 90 | 89 |
| Octave Bands-db re 10-12 Watts | ||||||||
| 12 | 87 | 80 | 73 | 68 | 65 | 63 | 62 | 61 |
| 25 | 94 | 86 | 79 | 74 | 71 | 69 | 68 | 67 |
| 50 | 100 | 92 | 85 | 80 | 77 | 75 | 74 | 73 |
| 100 | 106 | 98 | 91 | 86 | 83 | 81 | 80 | 79 |
- The minimum distance shall be measured in a straight line regardless of obstructions. Interpolated levels may be used for distances between those given in this table. See note (a) at end of Table 1207.2.1 in the New York City Building Code.
- In the event sound power level data for the exterior mechanical equipment is not available, the sound pressure levels, in octave bands, of the exterior mechanical equipment shall be measured.
- The measurements shall be obtained with the microphone of the measuring equipment located at the interior of the dwelling unit affected in a line with the window nearest the exterior mechanical equipment. The window shall be fully open and the microphone shall be located 3 feet away from the open portion of the window.
- Measurements shall be obtained during times when the ambient sound pressure levels, in octave bands, are at least 6db lower at all octave bands than the sound pressure levels measured with the exterior equipment operating. By ambient sound pressure levels is meant the measured sound pressure levels, at the above described measuring location, with the exterior equipment not in operation.