I was quite amazed at the way it does sound when in operation. When you turn it on, it starts off slowly then ramps up smoothly to full power - known as "soft start". This feature is normally only found on premium brands like Miele, who use it on most of their models. It saves wear on the motor and carbon brushes and cuts out the initial bright sparking of the brushes on the commutator, found on motors that don't use the soft start feature. On the Air3 Agile, the motor goes to full power as soon as its switched on, and you can observe 2 bright flashes from the brushes through the casing on immediate startup.
The Vax Zoom seems to sound like a flymo hover mower when running, a very different sound than I am used to for a budget vac.
Its not too loud either and quite a pleasant sound, without the high pitched scream of the Dyson DC07.
When lifting the front off the ground, you do get a rattle from the pile adjustment wheels, but otherwise its a very nice sounding vac. What also helps is that the exhaust filter is a thick round foam pad, that helps absorb motor noise, like a car exhaust silencer.
Compared to the Hoover whirlwind, this is a lot quieter. It is not as quiet as the Vax Mach Air though - you have to remember that the Mach Air uses a 1200W motor, so obviously it will run quieter. However, normally the Mach Air is much dearer to buy than the Zoom, and uses twin motors for brush and suction.
I have written my assessment on the Zoom based on the fact that it is one of the cheapest uprights that Argos sells, and for its price, its very good value.