General Decibel Information: The decibel (dB) is a logarithmic unit. You cannot add and subtract dB like ordinary numbers. An increase of 3dB is a doubling of the "strength" of the sound. An increase of 10dB means the sound is 10 times as loud. For example, 70dB is 10 times as loud as 60dB. All readings used the A-weighted decibels (dBA).

Methods: An exploratory study measuring the decibel levels for the Cold Air Drain® #1550 model with several available power options was conducted at the Shur Farms Frost Protection® manufacturing facility in Colton, California. Testing was conducted on July 8, 2010 between 7:00AM and 10:30AM. Each Cold Air Drain® model was tested in the same location at the facility on a level asphalt surface, with an aluminum building to the north of the testing area and a rail yard to the south of the testing area. The temperature was 58°F at start of testing and had risen to 70°F by the completion of the test, with 59% humidity (throughout the testing period). Decibel readings were taken using a Checkmate CM-130 on both the engine side and on the side directly opposite from the engine at a height of 5ft The ambient decibel level was measured at 5ft from the unit. Decibel readings were taken from 5ft to 150ft in 10ft increments. Actual decibel levels will likely be significantly lowered depending on soil type, ground cover, topography, obstructions (e.g., buildings, plants), temperature, and weather conditions.

Findings: Table 1 shows the decibel levels by distance from the Cold Air Drain® #1550 operating with each power unit. As the distance from the Cold Air Drain® unit increased, the decibel level decreased. The decibel level for each power unit tested was highest at 5ft from the engine for both the engine side and the side opposite the engine. The decibel levels at 5ft from each power unit on the engine side are comparable to the level of city traffic from inside a car (see Table 2). The decibel levels at 5ft from each power unit on the side opposite of the engine are comparable to the levels of a telephone dial tone (see Table 2). At a distance of 100ft the decibel levels for both the engine side and opposite the engine approximated the level of normal conversation (see Table 2). The findings from this exploratory study suggested that the Cold Air Drain®#1550 with each power unit may be significantly quieter than traditional wind machines (e.g., 90dB at 126ft1).