Fluorescent lighting fixtures produce a vibration (a slight buzzing sound) that originates in the
core and coil assembly of
fluorescent ballast. The buzzing sound can increase based on a variety of factors, including:
• The fashion in which the ballast is mounted in the fixture
• The design of the fluorescent lamp fixture
• Reverberating characteristics of the ceiling, walls, floors and furniture
• Ballast size: generally, the larger the ballast, the more humming it generates
One characteristic of iron-cored electromagnetic ballasts operating at 60 Hz, is the generation of audible noise. Noise can be increased by high temperatures, and it is amplified by certain luminaire designs. The best ballasts use high quality materials and workmanship to reduce noise. Noise is rated A, B, C, or D in decreasing order of preference. An "A" rated ballast will hum softly; a "D" rated ballast will make a loud buzz. The number of ballasts, their sound rating, and the nature of ambient noise in the room determine whether or not a system will create an audible disturbance.
Virtually all energy-efficient magnetic ballasts for F40T12 and F32T8 lamps are "A" rated, with a few exceptions, such as low temperature ballasts. Still, the hum of magnetic ballasts may be perceptible in a particularly quiet environment such as a library. Well-designed electronic high-frequency ballasts, on the other hand, should emit no perceptible hum. All electronic ballasts are "A" rated for sound.
To help sort through the variations, all ballasts carry a published sound rating of A, B, C, or D. These sound ratings are based on measurements of average ambient noise levels during conditions of normal occupancy. The following chart illustrates the average ambient noise level per application, and the corresponding recommended sound rating.
Ballast Losses:
A ballast, as an electric circuit, has electric energy losses.
Ballast losses are obtained from catalogues of ballast manufacturers.
Energy efficient ballasts have lower losses.
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