Speckle noise is inherent to laser barcode scanners since barcodes are usually printed on diffusive surfaces which generate speckle when illuminated by spatially coherent beams. In this paper statistical properties of barcode signals corrupted by speckle noise are analyzed. We derive closed form expressions for the autorcorrelation function and power spectral density of speckle noise for scanning beams with arbitrary field distributions. Since differentiation is often used for enhancement of barcode edges, we also analyze the properties of differentiated speckle noise. We derive estimates for signal-to-noise ratio when a laser beam scans over an edge. The random edge jitter in a barcode signal caused by speckle noise is also analyzed. The theory is illustrated by applying the results to Gaussian beams.