[Seany (OP)]

How do these work?

I'm guessing that the pitch or frequency, the sound of the vacuum cleaners give off, is duplicated and timed so that both sounds cancel each other out, thus making no sound..

IS that right?

[DoctorBeaver]

I doubt that. They're probably just using quieter engines & lower-friction bearings.

[another_someone]

Quiet or silent - not the same think (although, to be fair, many marketing men would ignore the distinction, and call something that was merely quiet as silent).

As Eth has said, I doubt very much that noise cancelling would be used.  Apart from everything else, it is difficult to get noise cancelling to work well over a large area (i.e. it may cancel noise in one location, but actually reinforce the noise in another location).

Reducing mechanical friction, and properly balancing rotating components would help; but since a fair amount of noise is just from air turbulance (which is also broad spectrum noise, so more difficult to electronically cancel out), I cannot see that being sufficient.

They could simply be putting acoustic foam liberally around the inside of the device (that is how much of the sound deadening is done for motor cars - but over time, the foam degrades, and so the device gets noisier as it gets older).

[Seany (OP)]

Quiet or silent - not the same think (although, to be fair, many marketing men would ignore the distinction, and call something that was merely quiet as silent).

I meant silent..

[Seany (OP)]

Quiet or silent - not the same think (although, to be fair, many marketing men would ignore the distinction, and call something that was merely quiet as silent).

As Eth has said, I doubt very much that noise cancelling would be used.  Apart from everything else, it is difficult to get noise cancelling to work well over a large area (i.e. it may cancel noise in one location, but actually reinforce the noise in another location).

Reducing mechanical friction, and properly balancing rotating components would help; but since a fair amount of noise is just from air turbulance (which is also broad spectrum noise, so more difficult to electronically cancel out), I cannot see that being sufficient.

They could simply be putting acoustic foam liberally around the inside of the device (that is how much of the sound deadening is done for motor cars - but over time, the foam degrades, and so the device gets noisier as it gets older).

Oh.. So they.. Can't really make a silent one, just yet?

[Seany (OP)]

I just hate the sound of my mum vacuuming [] Especially when I'm watching TV!