Sample Format for Acoustical Data

Manufacturer provided sound data typically comes in a wide variety of formats. Some manufacturers provide only one number to represent the total sound produced. These single numbers may come in sones, A-weighted sound levels dB(A), or bels. To better serve you, and provide a more accurate sound analysis, Lewis S. Goodfriend & Associates recommends that requests for manufacturer sound data be in one of the two following formats:

Table A - Octave-Band Sound-Power Levels (Lw) Produced by     (machine)     in
Normal Operation, at a Speed of               RPM.
Octave-Band
Center
Frequency, Hertz		 31.5 63 125 250 500 1000 2000 4000 8000
Lw, (dB re:  10-12 W)                  

or

Table B - Octave-Band Sound-Pressure Levels (Lp) Produced by     (machine)     at a Distance of           Feet from the        (face, edge, discharge, inlet)        in Normal Operation, at a Speed of               RPM.
Octave-Band
Center
Frequency, Hertz		 31.5 63 125 250 500 1000 2000 4000 8000
Lp, (dB re:  20 µPa)                  

The Following information should also be included when providing sound data to LSG&A:

Manufacturer’s name and model number for all mechanical equipment, including the capacity (air or fluid flow, static pressure or head), speed, drive motor size and speed and details on any special operating configurations, if applicable.

Drawings showing the location and elevations of the equipment as well as a site plan showing the layout of the site with respect to the neighboring property line(s). This information is necessary to calculate any attenuation that might be gained due to the distance to the property lines and the shielding from barriers or topography.

Manufacturer’s published octave-band sound-power level, Lw, or sound-pressure level, Lp, data in all four directions of the units. For fans and blowers, the data must include the case radiated (mechanical) sound power or sound-pressure levels of the units. All octave-band data must include levels in all nine (eight for fans and blowers) standard octave bands. Sound pressure levels should be given for distances greater than the largest diagonal measure of the unit or machine (usually 50 feet or greater is sufficient). Sound-pressure level data any closer will not be as useful for developing acoustical models, noise contours and expected property-line sound levels for comparison with codes and regulations.