@Sidekick - I wrote about this recently, here's a bit about funny noises, maybe something here will help
I’m hearing funny noises!
Gurgling, bubbling sounds.
Most often caused when e-liquid gets somewhere it’s not meant to be, most likely that the coil is flooded. Usually taking your tank apart and getting rid of excess juice then putting it all back together again will work. For a quick fix on the go use a twist of tissue paper to clear the coil/chimney of juice, or a short sharp blow into the drip tip can blow any excess juice out of the coil and through the air holes. Sometimes vaping at a slightly higher wattage can fix this problem – it may be that what you are hearing is e-liquid boiling and bubbling rather than being vaporized.
Crackling, hissing noises.
These types of noises are often heard using certain styles of coils, and is more noticeable when using a rebuildable or dripping atomizer. Clapton style coils, in particular due to their design, have a multitude of nooks and crannies, intended to create a large surface area on which juice can be vaporized. This often causes crackling and hissing, almost like a hot frying pan, it can be lessened by vaping at a higher wattage or temperature but not always. This is pretty normal and not really a cause for concern. However, if it bothers you then consider changing coil type.
Popping noises.
This sounds alarming when it happens, but is not really a cause for concern unless you are of a nervous disposition. It can indicate that juice is not being fully vaporized, in which case trying ramping up the wattage slightly, or it can be caused by e-liquid that is thin and/or has higher water content. This is common when e-juice is made using AG (Aqueous Glycerin) rather than Vegetable Glycerin (VG). AG is often used in place of VG to prevent high VG e-liquids from being excessively viscous, as it is much thinner than VG due to the addition of water. The presence of even this very small percentage of water can cause some scary noises when it ‘pops’ on a hot coil. However, the use of AG rather than pure VG is distinctly advantageous in ‘high VG’ E-liquids – it is far less likely to clog and gunk up your coil, meaning that juice wicking is more efficient, and coil longevity extended.
It is worth mentioning that hearing popping noises doesn’t necessarily mean that your e-liquid contains AG in place of VG, so please don’t jump to conclusions. VG is highly hygroscopic which means that it actively attracts water molecules from the air. This means that if your tank, or dripper, has sat unused for a while, or if you leave a bottle of e-juice open without a lid, any juice exposed to the air will have absorbed some extra water via natural means.
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Source)
). The noise can be a little off putting at first but if the vapour is smooth and enjoyable then it is the normal noise that a Sub Ohm tank makes 
