Definitions for "Crackles"
an adventitious breath sound heard on ausculating the chest, produced by air passing over airway secretions. A crackle is a discontinuous sound, as opposed to a wheeze, which is continuous. Crackles are known as fine or coarse and are also known as rales.
Fine particles of dirt, scratches or cinches in the negative, all result in showers of white spots on the print. These are heard as a background of clicks and crackles. Since white spots affect only the dark areas of the track, this noise is most noticeable during quiet passages where the bias line is narrowest. Noise during loud passages originates in the clear areas of the print. Loose dirt or scratches on the print, or an excessive and smeary application of lubricating wax to the print, are likely causes.