Tiggs

my marine tank has a few pumps in the tank that hum (as a pump does).....i wonder if the large cupboard under the tank is acting as a bass unit for this!

if i fit sound proof stuff inside the cupboard would that help? remeber, the pumps are NOT in the cupboard - they are in the tank ON the cupboard.

T

OllyK

My physics are rusty, but it sounds like the pumps may be setting up a harmonic resonance, which is being amplified by the open space in the cupboard.

See if you can feel the cupboard doors vibrating at all, if you can try duct taping them shut or tape some material to the inside of them. If this deadens the noise you can look to a more permenant solution. Maplins do rolls of dedening from Akasa for sound proofing PC cases for about £15 which may help.

ajm

Yes, as Olly said, if the natural frequency of the cabinet is near to that of the pumps then it can set up resonance. If this is the case then adding accoustic material like anechoic foam to the inside of the cupboard will have little effect.

To deaden the sound you will need to identify and stop any areas that may be vibrating like doors etc, and/or change the natural frequency of the cabinet! The only way to do this is to change the way mass is distributed within its structure!

Practically this could be as simple as putting some books on the shelf inside... trial and error!

Bear in mind the sound could be as a consequence of the natural frequency of the tank and cabinet together, in which case making these changes to the cabinet, being of fairly insignificant mass in comparison to the tank, may make little if any difference.

What kind of pumps are they? You say they are in the tank, are they literally submersed in the tank like powerheads? Attached to the glass?

BOB.T

What about putting summat between the tank and the cabinet, some of that non slip mat stuff with holes in

Tiggs

the pumps are submereged (theres 3 and they are fairly hefty)

i can feel vibes on the cupboard but VERY fait...i will try some sound deadening stuff inside and see what happens.

cant move thetank now- it weighs half a ton!

OllyK

If you can feel the vibration it is probably a low'ish frequency and the open space in the cupboard is acting as an amplifier. As suggested, experiment with tape and weight to see if you can deaden it, also see if you can attach the pumps more firmly to the tank

Tiggs

everything is very sturdy and nothing is vibrating because its "loose" as such.

will sound deadening stuff in the cupboard space not "absorb" the noisy sound waves? (must have missed this at school!)

OllyK

Please refer to my opening post about sketchy physics

I think the sound deadening can help in terms of reducing the vibration of the element it is stuck to, so it will stop the sides of the cupboard from vibrating but not the air in it. Are there and loose shelves in the cupboard? Have the doors got little rubber feet to stop them banging against the carcass?

I'd be tempted to eliminate any loose stuff first before stickining deadening to the inside.