For most people the best way to buy the ducting for their rangehood installation is by choosing the appropriate kit for the job, usually one for wall, soffit or roof. A good quality kit contains what you need for a standard installation such as those illustrated above. If your rangehood ducting reaquirements are not so straightforward the of course a kit is not for you and you'll have to buy individual parts.
Remember that ducting kits do not have to be brand specific so you are free to choose pretty much any brand that suits your budget and preference. But do remember to buty the correct size of kit for your rangehood (usually 125mm or 150mm). It would be acceptable to go bigger but never smaller.
A a ducting kit incorporating silencer or muffler will reduce significantly the noise generated by your rangehood. It is placed first in the ducting line directly attached to the rangehood where the air exits: the noisiest part. Ducting kits are available that incorporate a muffler, such as Rangehood Tamer.
Ducting a wall mounted rangehood generally means venting through either the wall, roof or soffit for which there are convenient kits.
Wall venting is suitable for both rear vented and top vented rangehoods and canopies. Probably the simplest way to vent a rangehood mounted on an outside wall.
With no acute bends to cause back pressure, roof venting is the most efficient way to vent a rangehood.as it allows the rangehood to operate to its full capacity.