§ 27-770 Noise control of mechanical equipment.
AC § 27-770
(a)Minimum airborne noise insulation requirements.
(1)BOILER ROOMS. Boiler rooms adjoining dwelling spaces, either vertically or horizontally, shall be separated therefrom by floor-ceiling or partition constructions having a minimum STC rating of fifty.
(2)MECHANICAL EQUIPMENT SPACES. Spaces or shafts containing air conditioning, refrigeration, or ventilating equipment, elevator machinery, or other mechanical equipment shall be separated both vertically and horizontally from dwelling units by constructions that will provide a minimum STC rating of fifty. Spaces or shafts containing equipment totaling more than seventy-five rated h.p. shall not be located vertically or horizontally adjacent to dwelling units unless the total sound power level output of all the equipment in the space or shaft is certified not to exceed the maximum sound power levels of table 12-3 in any octave band. Such sound power level ratings shall be obtained by tests conducted in accordance with the procedures of reference standard RS 12-5. a. Ventilating openings into mechanical equipment spaces. Ventilating openings into boiler rooms and other mechanical equipment spaces shall not be located in yards or courts where there are windows opening from living quarters, unless such ventilating openings are provided with sound attenuating devices if needed to limit noise transmission to NC-40 (noise criterion) levels in the exposed dwelling units. For permits issued after January first, nineteen hundred seventy-two, the permissible noise levels shall not exceed NC-35. b. Noise criteria requirements. Noise criteria requirements prescribed in this subchapter shall be in accordance with reference standard RS 12-4. TABLE 12-3Maximum Sound Power Levels Permitted in MechanicalSpaces or Shafts Adjoining Dwelling Spaces Octave Bands, c.p.s. Mid-FrequencyMax. Sound Power Level db adb re 10 -13 Wattsdb re 10 -12 Watts 63 101 91 125 101 91 250 103 93 500 105 95 1,000 102 92 2,000 101 91 4,000 98 88 8,000 96 86 Notes for Table 12-3: a The maximum sound power levels shall be reduced five db in any octave band where the equipment data indicate pure tone generation. The presence of pure tones may be determined by means of one-third octave band analysis. The criterion for a significant pure-tone component shall be an audible pure-tone sound together with an increase of the sound pressure level in the corresponding one-third octave band above the mean of the two adjacent one-third of at least: Center frequency of one-third octave band40/125160/250215/19500630/1,0001,000/10,000Increase in sound pressure level (db)64321 1/2 b For permits issued after January first, nineteen hundred seventy-two, the maximum sound power levels shall be changed as follows: Octave Bands, c.p.s. Mid-Frequencydb re 10-13 Wattsdb re 10-12 Watts 63 98 88 125 97 87 250 100 90 1,000 97 87 2,000 96 86 4,000 93 83 8,000 91 81 (3) DUCTWORK. Ducts serving dwelling units shall be lined with duct lining for at least twenty feet from the fan discharge or intake; otherwise, an approved sound attenuating device shall be installed therein. All toilet exhaust ducts shall be lined with duct lining for at least twenty feet upstream of the exhaust fan intake, otherwise, an approved sound attenuating device shall be installed therein. Duct lining shall conform to the requirements of subchapter thirteen of this chapter.
(4)EXTERIOR MECHANICAL EQUIPMENT. 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 12-4 where one or more windows of a dwelling unit in any building in occupancy groups J-1, J-2, or J-3 is located within a sphere of one hundred foot radius 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 12-5.
(b)Minimum structure-borne noise and vibration isolation requirements. All isolators used in accordance with the following requirements shall be approved. Table 12-4Maximum Sound Power Levels Permitted for ExteriorMechanical Equipment Adjoining Buildings b Minimum Distance from Equipment to Exterior Window (ft.) aMaximum Sound Power Levels in Octave Bands-db re 10-13 Watts aOctave Bands c.p.s. Mid Frequency631252505001,0002,0004,0008,000129992888482828282 25 103 96 92 88 86 86 86 86 50 107 100 96 92 90 90 90 90 100 110103999593939393 in Octave Bands-db re 10-12 Watts12 89 82 78 74 72 72 72 72 25 93 86 82 78 76 76 76 76 50 97 90 86 82 80 80 80 80 100 100 93 89 85 83 83 83 83 Notes for Table 12-4: a 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 12-3.
1.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.
2.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 three ft. away from the open portion of the window.
3.Measurements shall be obtained during times when the ambient sound pressure levels, in octave bands, are at least six db 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. b For permits issued after January first, nineteen hundred seventy-two, the permitted maximum sound power levels for exterior mechanical equipment adjoining buildings shall be changed as follows: Maximum Sound Power Levels in Feet Octave Bands-db re 10-13 Watts 631252505001,0002,0004,0008,000129790837875737271 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 in Octave Bands-db re 10-12 Watts12 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 Table 12-5Noise Output Limitations for Exterior Mechanical EquipmentMaximum Sound Pressure Level a, b(Not to be exceeded in any octave bands) Octave Bands Center Frequencies (cps)Decibels re .0002 Microbar 63 64 125 57 250 51 500 45 1,000 41 2,000 39 4,000 38 8,000 37 Notes for Table 12-5: a 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. The equipment used shall meet the requirements of reference standards RS 12-6. b For permits issued after January first, nineteen hundred seventy-two, the maximum sound pressure levels shall be changed as follows: Octave Bands Center Frequencies (cps)Decibels re .0002 Microbar 63 61 125 53 250 46 500 40 1,000 36 2,000 34 4,000 33 8,000 32 (b) Minimum structure-borne noise and vibration isolation requirements. All isolators used in accordance with the following requirements shall be approved.
(3)PIPING. a. Metal piping connected to power driven equipment shall be resiliently supported from or on the building structure for a distance of fifty pipe diameters from the power driven equipment. The resilient isolators shall have a minimum static deflection of one inch for all piping with a four inch or larger actual outside diameter and one-half inch for piping with less than four inches in actual outside diameter. Piping connected to fluid pressure-reducing valves, shall be resiliently isolated for a distance of fifty pipe diameters from pressure reducing valves and isolators shall provide a minimum static deflection of one-half inch. b. Equipment such as heat exchangers, absorption refrigeration machines, etc., that is located on any floor or roof other than a floor on grade, and that is not power driven but is connected by metal piping to power driven equipment, shall be resiliently supported from or on the building structure, for a distance of fifty pipe diameters from the power driven equipment. The resilient supports shall be vibration isolators having a minimum static deflection of one inch and shall incorporate approved resilient pads having a minimum thickness of one-quarter inch.
(5)PUMPS. All pumps of three h. p. or more located on any floor other than a floor on grade shall be supported on vibration isolators having a minimum isolation efficiency of eighty-five per cent at the lowest disturbing frequency. Each isolator shall incorporate a leveling device and a resilient pad having a minimum thickness of one-quarter inch.
(6)COMPRESSORS. Compressors and drives located on a floor other than a floor on grade shall be mounted on vibration isolators having a minimum isolation efficiency of eighty-five per cent at the lowest disturbing frequency. Each isolator shall incorporate a leveling device and a resilient pad having a minimum thickness of one-quarter inch.
(7)COOLING TOWERS. All moving parts of cooling towers located on a roof or floor other than a floor on grade shall be installed on vibration isolators providing a minimum isolation efficiency of eighty-five per cent at fan rotor rpm with a maximum static deflection of four inches. Each isolator shall incorporate a leveling device and a resilient pad having a minimum thickness of one-quarter inch.
(8)EVAPORATIVE CONDENSERS. Evaporative and air cooled condensers located on a roof or floor other than a floor on grade shall be mounted on vibration isolators providing a minimum isolation efficiency of eighty-five per cent at fan rotor rpm with a maximum static deflection of four inches. Each isolator shall incorporate a leveling device and a resilient pad having a minimum thickness of one-quarter inch.
(9)DUCT CONNECTIONS TO FAN EQUIPMENT. Flexible connections shall be installed between fan equipment and connecting ductwork.
(10)ELEVATOR MACHINERY. Gear-driven machinery, gearless machinery, motor generators, and controllers located in an elevator machinery room or shaft on a roof, or on a floor other than a floor on grade, shall be supported on vibration isolator pads having a minimum thickness of one-half inch.
(c)Maximum permissible air velocities in ducts.
(d)Maximum permissible sound power levels of fan coil units, grilles, registers, diffusers and induction units. Sound power level data, in octave bands, shall be certified in accordance with the provisions of section 27-131 of article seven of subchapter one of this chapter, for grilles, registers, diffusers and induction units at design operating conditions and for coil units when operating at specified cfm. The sound power levels shall not exceed the levels listed in table 12-7 when measured in accordance with the provisions of reference standard RS 12-5. TABLE 12-7Maximum Permissible Sound Power Levels for Terminal Units1 Octave Bands, c.p.s. Mid-FrequencySound Power Levels, dbdb re 10-13 db re 10-12 Watts 63 79 69 125 73 63 250 67 57 500 62 52 1,000 59 49 2,000 57 47 4,000 54 44 8,000 53 43 Notes for Table 12-7: 1 For permits issued after January first, nineteen hundred seventy-two, the Maximum Permissible Sound Power Level for terminal units shall be changed as follows: Octave Bands, c.p.s. Mid FrequenciesSound Power LevelsdB re 10-13 db re 10-12 Watts 63 76 66 125 69 59 250 62 52 500 57 47 1,000 54 44 2,000 52 42 4,000 49 39 8,000 48 38
