All sound supressors have to be purchased over the counter on production of ID and have to be entered in the register and are not available for Mail Order
A silencer contains baffles which "shred" the sound waves - these types tend to be a little more expensive (£40-£60) than the
Sound Moderator, which causes the sound wave to bounce back on itself which "cancels out" the sound. (£30-£40)
A Silencer completely removes the sound, whereas a sound moderator prevents the sound from carrying on over a distance but appears not to cancel the sound to the shooter. ( I use the concept of two wet wood blocks knocked together give a muffled sound)
The VCR act 2006 includes silencers and moderators in the restricted purchases requirement of over the counter purchase with ID, and details entered into statutory register with thanks to Jacqui Smith (bye).