The noisiest skylights are single-paned and provide the least insulation from outside noises. If your skylight is single-paned, replacing it with a double- or triple-paned skylight will sharply dampen the noise. If your skylight is already double- or triple-paned and noise is still an issue, fiberglass insulation will further reduce noise.
Determine the number of panes in your skylight. You can do this visually. The panes are parallel to each other, so you can see the edges of the glass if you look from an oblique angle.
If your skylight is single-paned, it will allow a lot of ambient external noise to pass through it, and will amplify the sound of any noisy occurrences, such as rain drops, birds and debris that may land on the window. Plastic bubble skylights -- as opposed to flat pane skylights -- are the thinnest and noisiest type.
Replace single-paned skylights with double-paned or triple-paned skylights, if applicable. This will drastically reduce both your noise issues and your heating and cooling bills. Select a double- or triple- paned skylight from your local hardware store, which will most likely offer installation for an additional price.
Purchase fiberglass insulation at your local hardware store. Layer it around the skylight shaft. This will help dampen the noise. If your skylight is already double-paned or triple-paned, this is the best method for further reducing noise.
Consider adding a thick blind to your skylight. While this will block out the light, it also will help to deaden the exterior noises.