soundproofing a buzzing box

[John Richer]

I have a noisy box of mains-fed electronics in a cupboard that I would
like to soundproof. (It makes a faint but annoying buzzing noise,
presumably the power supply). Any suggestions? The box is about
30x30x10cm. I was thinking about fitting a plasterboard or MDF box
around it. Has anyone done anything similar and care to give some
advice? An obvious concern is that sound and thermal insulation tend to
go hand in hand, so overheating could be an issue.

[Andy Hall]

Post by John Richer
I have a noisy box of mains-fed electronics in a cupboard that I would
like to soundproof. (It makes a faint but annoying buzzing noise,
presumably the power supply). Any suggestions? The box is about
30x30x10cm. I was thinking about fitting a plasterboard or MDF box
around it. Has anyone done anything similar and care to give some
advice? An obvious concern is that sound and thermal insulation tend to
go hand in hand, so overheating could be an issue.

How about a different approach.

Replace the transformer and power supply in the electronics with a
switched mode one. These are readily available from RS, Maplin and
all the other suspects quite inexpensively.

This would avoid the need to make a box because it would be silent and
you would avoid heat problems as well.




.andy

To email, substitute .nospam with .gl

[Grunff]

Post by Andy Hall
Replace the transformer and power supply in the electronics with a
switched mode one. These are readily available from RS, Maplin and
all the other suspects quite inexpensively.

Andy, I'm shocked! I *hate* switchers, and view them a necessary evil,
to be avoided wherever possible. Much more highly stressed than a good
old fashioned transformer/rectifier/regulator setup. And sooo noisy
(electrically).

[Dave Plowman]

Post by Grunff

Post by Andy Hall
Replace the transformer and power supply in the electronics with a
switched mode one. These are readily available from RS, Maplin and
all the other suspects quite inexpensively.

Andy, I'm shocked! I *hate* switchers, and view them a necessary evil,
to be avoided wherever possible. Much more highly stressed than a good
old fashioned transformer/rectifier/regulator setup. And sooo noisy
(electrically).

A change from a 'normal' transformer to a toroidal one will usually cure
noise. Anything with steel in it will often vibrate in sympathy with the
stray magnetic field from a 'normal' one, and toroids are very much better
in this respect.

[Grunff]

Post by Dave Plowman
A change from a 'normal' transformer to a toroidal one will usually cure
noise. Anything with steel in it will often vibrate in sympathy with the
stray magnetic field from a 'normal' one, and toroids are very much better
in this respect.

I do like toroidal transformers. I use them whenever there's one
available for the application, which thankfully these days is most cases.

[Andy Hall]

Post by Grunff

Post by Andy Hall
Replace the transformer and power supply in the electronics with a
switched mode one. These are readily available from RS, Maplin and
all the other suspects quite inexpensively.

Andy, I'm shocked! I *hate* switchers, and view them a necessary evil,
to be avoided wherever possible. Much more highly stressed than a good
old fashioned transformer/rectifier/regulator setup. And sooo noisy
(electrically).

If you don't run them near the limit and pick a good quality one,
still not expensive, then they are fine.

In terms of emissions, you can pick units to various levels - e.g. for
domestic or office applications.

I wouldn't normally pick a switching supply in an audio or an RF
design, though. Having said that, in the distant past, I have
designed a switching supply into HF and VHF radio communications rigs.
It can be done, but requires some diligent attention to screening.

For the type of application here, a burglar alarm, there's no reason
not to use a switching supply, although if the present arrangement has
the rectifier/regulator components on a circuit board, it might be
easier to exchange the transformer for a toroidal type as others have
suggested.


.andy

To email, substitute .nospam with .gl

[G&M]

Post by Andy Hall

Post by Grunff
Andy, I'm shocked! I *hate* switchers, and view them a necessary evil,
to be avoided wherever possible. Much more highly stressed than a good
old fashioned transformer/rectifier/regulator setup. And sooo noisy
(electrically).

If you don't run them near the limit and pick a good quality one,
still not expensive, then they are fine.
I wouldn't normally pick a switching supply in an audio
design, though.

Provided you sync the switcher to the sampling frequency (assuming digital
audio source) there is no problem. Most professional audio gear is going
this way now with a couple of notable exceptions.

[Christian McArdle]

Post by Grunff
Andy, I'm shocked! I *hate* switchers, and view them a necessary evil,
to be avoided wherever possible.

Nah. Nothing beats a well designed switch mode. They don't have to be
electrically noisy. In fact, nowadays, they are required not to be.

Imagine how big and heavy your computer would be with a torroidal. That
would be a pretty heavily heatsinked 7805, too!

Christian.

[Grunff]

Post by Christian McArdle
Imagine how big and heavy your computer would be with a torroidal. That
would be a pretty heavily heatsinked 7805, too!

That's exactly the 'necessary evil' I'm talking about.

[geoff]

In message <***@uni-berlin.de>, Grunff <***@ixxa.com>
writes

Post by Grunff

Post by Andy Hall
Replace the transformer and power supply in the electronics with a
switched mode one. These are readily available from RS, Maplin and
all the other suspects quite inexpensively.

Andy, I'm shocked! I *hate* switchers, and view them a necessary evil,
to be avoided wherever possible. Much more highly stressed than a good
old fashioned transformer/rectifier/regulator setup. And sooo noisy
(electrically).

Is it the transformer which is making the noise because of loose
laminations?

If so, buy some pcb lacquer and spray the bugger

[G&M]

Post by Grunff

Post by Andy Hall
Replace the transformer and power supply in the electronics with a
switched mode one. These are readily available from RS, Maplin and
all the other suspects quite inexpensively.

Andy, I'm shocked! I *hate* switchers, and view them a necessary evil,
to be avoided wherever possible. Much more highly stressed than a good
old fashioned transformer/rectifier/regulator setup.
And sooo noisy (electrically).

Uh ? For high power products, a linear PSU is technically illegal as it
puts such high phase and harmonic distortions back onto the line.

[Roly]

Post by Andy Hall

Post by John Richer
I have a noisy box of mains-fed electronics in a cupboard that I would
like to soundproof. (It makes a faint but annoying buzzing noise,
presumably the power supply). Any suggestions? The box is about
30x30x10cm. I was thinking about fitting a plasterboard or MDF box
around it. Has anyone done anything similar and care to give some
advice? An obvious concern is that sound and thermal insulation tend to
go hand in hand, so overheating could be an issue.

How about a different approach.
Replace the transformer and power supply in the electronics with a
switched mode one. These are readily available from RS, Maplin and
all the other suspects quite inexpensively.
This would avoid the need to make a box because it would be silent and
you would avoid heat problems as well.

Replacing the power supply with a switched mode one will certainly do
the trick, but it might be that no off-the-shelf PSU would be suitable
and you'd need to find alternative solutions.

You could try using anti-vibration techniques to prevent the box and
supporting structure from amplifying the noise.

If the PSU is a separate assembly, use rubber grommets clamped loosely
between large washers to dampen the vibration. The less weight that is
supported by the anti-vibration system, the better.

[Dave Plowman]

Post by Roly
Replacing the power supply with a switched mode one will certainly do
the trick, but it might be that no off-the-shelf PSU would be suitable
and you'd need to find alternative solutions.

I'm no expert on alarms but most seem to have a 12 volt battery as back
up, so will be pretty standard.

[N. Thornton]

Post by Andy Hall

Post by John Richer
I have a noisy box of mains-fed electronics in a cupboard that I would
like to soundproof. (It makes a faint but annoying buzzing noise,
presumably the power supply). Any suggestions? The box is about
30x30x10cm. I was thinking about fitting a plasterboard or MDF box
around it. Has anyone done anything similar and care to give some
advice? An obvious concern is that sound and thermal insulation tend to
go hand in hand, so overheating could be an issue.

How about a different approach.
Replace the transformer and power supply in the electronics with a
switched mode one. These are readily available from RS, Maplin and
all the other suspects quite inexpensively.
This would avoid the need to make a box because it would be silent and
you would avoid heat problems as well.

or just replace it with a standard linear one that doesnt buzz. Most
dont. If it uses a separate plug in supply that is.

Is the buzzing thing mounted on plasterboard or solid wall? If PB,
then mounting it solidly to the brick wall could make all the
difference, it may be using the PB as a sounding board.


Regards, NT

[G&M]

Post by Andy Hall

Post by John Richer
I have a noisy box of mains-fed electronics in a cupboard that I would
like to soundproof. (It makes a faint but annoying buzzing noise,
presumably the power supply). Any suggestions? The box is about
30x30x10cm. I was thinking about fitting a plasterboard or MDF box
around it. Has anyone done anything similar and care to give some
advice? An obvious concern is that sound and thermal insulation tend to
go hand in hand, so overheating could be an issue.

How about a different approach.
Replace the transformer and power supply in the electronics with a
switched mode one.

Odd - I was about to consider replacing the switched mode PSU in our Stoves
touch control hob which whistles annoyingly with a linear wall wart.

[Andy Hall]

Post by G&M

Post by Andy Hall

Post by John Richer
I have a noisy box of mains-fed electronics in a cupboard that I would
like to soundproof. (It makes a faint but annoying buzzing noise,
presumably the power supply). Any suggestions? The box is about
30x30x10cm. I was thinking about fitting a plasterboard or MDF box
around it. Has anyone done anything similar and care to give some
advice? An obvious concern is that sound and thermal insulation tend to
go hand in hand, so overheating could be an issue.

How about a different approach.
Replace the transformer and power supply in the electronics with a
switched mode one.

Odd - I was about to consider replacing the switched mode PSU in our Stoves
touch control hob which whistles annoyingly with a linear wall wart.

If it whistles, there's something wrong with it or it's a crap design.



.andy

To email, substitute .nospam with .gl

[G&M]

Post by Andy Hall

Post by G&M

Post by Andy Hall

Post by John Richer
I have a noisy box of mains-fed electronics in a cupboard that I would
like to soundproof. (It makes a faint but annoying buzzing noise,
presumably the power supply). Any suggestions? The box is about
30x30x10cm. I was thinking about fitting a plasterboard or MDF box
around it. Has anyone done anything similar and care to give some
advice? An obvious concern is that sound and thermal insulation tend to
go hand in hand, so overheating could be an issue.

How about a different approach.
Replace the transformer and power supply in the electronics with a
switched mode one.

Odd - I was about to consider replacing the switched mode PSU in our Stoves
touch control hob which whistles annoyingly with a linear wall wart.

If it whistles, there's something wrong with it or it's a crap design.

I was assuming the later.

[Ian Stirling]

Post by John Richer
I have a noisy box of mains-fed electronics in a cupboard that I would
like to soundproof. (It makes a faint but annoying buzzing noise,
presumably the power supply). Any suggestions? The box is about
30x30x10cm. I was thinking about fitting a plasterboard or MDF box
around it. Has anyone done anything similar and care to give some
advice? An obvious concern is that sound and thermal insulation tend to
go hand in hand, so overheating could be an issue.

What is it?
Sumply replacing the transformer may help.

[John Richer]

Post by John Richer
I have a noisy box of mains-fed electronics in a cupboard that I
would like to soundproof. (It makes a faint but annoying buzzing
noise, presumably the power supply).

[snip]

What is it? Sumply replacing the transformer may help.

Thanks for the suggestions so far. It's a burglar alarm box, so I
really don't want to tamper with it. I know the final solution is to
relocate the box elsewhere - cellar or so - but that's a full reinstall
ad I'd like to avoid if possible.

So, any suggestions for soundproofing experience will still be gladly
received!

[Grunff]

Post by John Richer
Thanks for the suggestions so far. It's a burglar alarm box, so I
really don't want to tamper with it.

I think that's even more reason to tamper - it will be a very simple
single voltage supply, and quite low power. Swapping it out for a
quieter one is likely to be very easy.

[Dave Plowman]

Post by Grunff

Post by John Richer
Thanks for the suggestions so far. It's a burglar alarm box, so I
really don't want to tamper with it.

I think that's even more reason to tamper - it will be a very simple
single voltage supply, and quite low power. Swapping it out for a
quieter one is likely to be very easy.

Could be it's on rental, of course, in which case complain to the supplier.

[Ian Stirling]

Post by John Richer

Post by John Richer
I have a noisy box of mains-fed electronics in a cupboard that I
would like to soundproof. (It makes a faint but annoying buzzing
noise, presumably the power supply).

[snip]

What is it? Sumply replacing the transformer may help.

Thanks for the suggestions so far. It's a burglar alarm box, so I
really don't want to tamper with it. I know the final solution is to
relocate the box elsewhere - cellar or so - but that's a full reinstall
ad I'd like to avoid if possible.
So, any suggestions for soundproofing experience will still be gladly
received!

Hokaay...
So, modifying boxes you don't own is generally frowned on.
Do you need to get to the box easily, does it have a battery in, how many
cables lead to it, can you disconnect and reconnect the cables, does it
get warm.

[geoff]

Post by John Richer

Post by John Richer
I have a noisy box of mains-fed electronics in a cupboard that I
would like to soundproof. (It makes a faint but annoying buzzing
noise, presumably the power supply).

[snip]

What is it? Sumply replacing the transformer may help.

Thanks for the suggestions so far. It's a burglar alarm box, so I
really don't want to tamper with it.

Which will have a tamper switch in it

[John Richer]

Post by geoff

Post by John Richer
Thanks for the suggestions so far. It's a burglar alarm box, so
I really don't want to tamper with it.

Which will have a tamper switch in it

That figures, and further confirms my view that I either soundproof it
externally with some MDF/plasterboard/magic material, or go back to the
installers.

I was mainly hoping for help on the sound deadening properties of
various materials, but the stuff on PSUs has been interesting...

[geoff]

Post by John Richer

Post by geoff

Post by John Richer
Thanks for the suggestions so far. It's a burglar alarm box, so
I really don't want to tamper with it.

Which will have a tamper switch in it

That figures, and further confirms my view that I either soundproof it
externally with some MDF/plasterboard/magic material, or go back to the
installers.
I was mainly hoping for help on the sound deadening properties of
various materials, but the stuff on PSUs has been interesting...

What you need is some anti sound ...

[Grunff]

Post by geoff
What you need is some anti sound ...

Hey, that's a good idea - an active noise cancelling device. Pretty
readily available these days.

[wanderer]

Post by John Richer

Post by geoff

Post by John Richer
Thanks for the suggestions so far. It's a burglar alarm box, so
I really don't want to tamper with it.

Which will have a tamper switch in it

That figures, and further confirms my view that I either soundproof it
externally with some MDF/plasterboard/magic material, or go back to the
installers.

Has the control box been installed on a wooden partition wall, by any
chance? If so that could be acting like a sounding board. Best bet then
would be to get the installers back and put a suitable fibre board
underneath to dampen the sound.

[Andrew Collins]

Post by wanderer
Has the control box been installed on a wooden partition wall, by any
chance? If so that could be acting like a sounding board. Best bet then
would be to get the installers back and put a suitable fibre board
underneath to dampen the sound.

IME very few electrical devices produce a disturbing amount of hum on
their own. It is normally due to them being mounted on something that is
acting as a sounding board.

You should be able to feel this :- put your fingertips on the wall next
to the box, if it's vibrating then this is likely to be your problem.
If you now push on the wall, does the sound reduce?

If it does then your problem is the wall acting as a sounding board. If
it doesn't then I'm about to waffle a load of irrelevant crap. Also bear
in mind that I've never had this exact problem, but many years ago I
used to design speaker cabinates so I know a bit about acoustics and
resonance.

Assuming you can't move the box much there are two basic approaches.

1) Changing the way the box is mounted so that the vibrations are not
transferred. Putting soft rubber washers in everywhere you can may help,
but they will need to be quite thick.

2) Stop the board from resonating at the annoying frequency. Anything
you can do to make the panel heavier in one place, lighter in one place,
stiffer, more flexible, larger, smaller, in short any way you can change
the physical properties of the panel will alter the acoustic properties
and may well reduce the resonance - or make it worse!
Taking a wild stab in the dark, but is it mounted on a panel on the
outside of your cupboard under the stairs? If so then putting some sort
of bar across near the centre of the board on which it is mounted may
well significantly reduce the resonance, I say near the centre
deliberately, avoid putting it at the exact centre. You can probably
mount it on the back out of harm's way.

By far the best solution though is to mount it on something that will
not resonate at any annoying frequency.

HTH!

--
Andrew

[John Richer]

Post by Andrew Collins

Post by wanderer
Has the control box been installed on a wooden partition wall, by
any chance? If so that could be acting like a sounding
board. Best bet then would be to get the installers back and put
a suitable fibre board underneath to dampen the sound.

IME very few electrical devices produce a disturbing amount of hum
on their own. It is normally due to them being mounted on
something that is acting as a sounding board.

Thanks for the suggestions so far. For clarity, the metal box is
mounted on the side a large brick chimney stack, presumably screwed in
with Rawlplugs, and feels pretty securely mounted. Being relcutant to
take it to pieces for obvious reasons, I can't be sure, but it appears
to me that the hum is internal to the box, and local to the PSU, and not
resonating any obviously loose material except the case itself.

[Dave Plowman]

Post by John Richer
Thanks for the suggestions so far. For clarity, the metal box is
mounted on the side a large brick chimney stack, presumably screwed in
with Rawlplugs, and feels pretty securely mounted. Being relcutant to
take it to pieces for obvious reasons, I can't be sure, but it appears
to me that the hum is internal to the box, and local to the PSU, and not
resonating any obviously loose material except the case itself.

Is the box steel? If so, I'd definitely say it's induced stray magnetism
from the transformer. In other words, poor design.

[Ian Middleton]

Post by Dave Plowman

Post by John Richer
Thanks for the suggestions so far. For clarity, the metal box is
mounted on the side a large brick chimney stack, presumably screwed in
with Rawlplugs, and feels pretty securely mounted. Being relcutant to
take it to pieces for obvious reasons, I can't be sure, but it appears
to me that the hum is internal to the box, and local to the PSU, and not
resonating any obviously loose material except the case itself.

Is the box steel? If so, I'd definitely say it's induced stray magnetism
from the transformer. In other words, poor design.
--
*Does fuzzy logic tickle? *
RIP Acorn

My alarm box in my new house airing cupboard, buzzed quite loudly.
"wobbling" the transformer changed the noise, the transfomer "buzz" was
being coupled into the steel case. I unbolted the transformer and inserted a
couple of sheets of plastic made from margerine tub lids (Vitalite I think)
and now it is virtually silent.

Very easy to do, especially if you just cut slits in the plastic, rather
than holes, the sheets can be just be slid behind the transformer and fixing
bolts re-tightened.

[Dave Plowman]

Post by Ian Middleton
My alarm box in my new house airing cupboard, buzzed quite loudly.
"wobbling" the transformer changed the noise, the transfomer "buzz" was
being coupled into the steel case. I unbolted the transformer and
inserted a couple of sheets of plastic made from margerine tub lids
(Vitalite I think) and now it is virtually silent.
Very easy to do, especially if you just cut slits in the plastic, rather
than holes, the sheets can be just be slid behind the transformer and
fixing bolts re-tightened.

You're lucky as that was pure mechanical noise. If it's induced stray
magnetism, there's not much you can do about it easily.

[Ian Stirling]

Post by Dave Plowman

Post by Ian Middleton
My alarm box in my new house airing cupboard, buzzed quite loudly.
"wobbling" the transformer changed the noise, the transfomer "buzz" was
being coupled into the steel case. I unbolted the transformer and
inserted a couple of sheets of plastic made from margerine tub lids
(Vitalite I think) and now it is virtually silent.
Very easy to do, especially if you just cut slits in the plastic, rather
than holes, the sheets can be just be slid behind the transformer and
fixing bolts re-tightened.

You're lucky as that was pure mechanical noise. If it's induced stray
magnetism, there's not much you can do about it easily.

Of course there is.
If you stop the bit making noise moving, then it does not make noise.

Do NOT open microwaves without knowing what you are doing.
The stored energy and high voltage makes them easily the most lethal
bit of home electronics to attempt to service.

I had a microwave that made an annoying banging when first turned on,
and then a loud buzz.
This was due to the case next to the transformer being bent inwards
due to the induced magnetism.

Opened it up, added a bit of 6mm ply 200*200mm to the case next to the
transformer, glued it on, and the problem largely went away.

[Dave Plowman]

Post by Ian Stirling

Post by Dave Plowman
You're lucky as that was pure mechanical noise. If it's induced stray
magnetism, there's not much you can do about it easily.

Of course there is.
If you stop the bit making noise moving, then it does not make noise.

Difficult when it's often the whole casing. Best to clad it in 3" thick
concrete. That works well.

[Pete C]

Post by John Richer
Thanks for the suggestions so far. It's a burglar alarm box, so I
really don't want to tamper with it. I know the final solution is to
relocate the box elsewhere - cellar or so - but that's a full reinstall
ad I'd like to avoid if possible.
So, any suggestions for soundproofing experience will still be gladly
received!

Hi,

What make is it? Have you tried contacting the manufacturer directly
and getting their opinion on it?

cheers,
Pete.

[John Richer]

Post by Dave Plowman

Post by John Richer
Thanks for the suggestions so far. It's a burglar alarm box,

so I > really don't want to tamper with it.
I think that's even more reason to tamper - it will be a very
simple single voltage supply, and quite low power. Swapping it
out for a quieter one is likely to be very easy.

Could be it's on rental, of course, in which case complain to the
supplier.

It belongs to the property, but it is new. "They all make that noise"
the engineer helpfully told me. Don't fancy mucking with it myself, so
will either pursue the soundproofing option, or complain more
vociferously.