Hi,
I have a constant 50Hz humming from an AC compressor when it's almost on full power. The AC aleady got additional dampened with new rubber feet and a sound dampening enclosure, but my walls are very thin. The humming is bearly hearable but i can notice it when there is silence.
Is there are a cheap way to dampen more of the 50Hz noise?
Especially with a heavy cloud panel, or bass traps?
I could also do walls, but i'm limited on the thickness.
thank you
I have a constant 50Hz humming from an AC compressor when it's almost on full power. The AC aleady got additional dampened with new rubber feet and a sound dampening enclosure, but my walls are very thin. The humming is bearly hearable but i can notice it when there is silence.
Is there are a cheap way to dampen more of the 50Hz noise?
Especially with a heavy cloud panel, or bass traps?
I could also do walls, but i'm limited on the thickness.
thank you
This sounds like an application for a Helmholtz resonator. These can be built quite inexpensively. Here is an example of a turn-key product/service:
https://www.ekustik.eu/catalog/woody-resonator
There are Helmholtz calculators on the web that you can use to help you design your own, such as:
https://www.omnicalculator.com/physics/helmholtz-resonator
http://www.acousticmodelling.com/helmholtz.php
https://www.calctool.org/waves/helmholtz-resonator
An old diyAudio thread:
https://www.diyaudio.com/community/threads/helmholtz-resonator-inside-a-sealed-cabinet.219863/
I'd also recommend looking at placing a resonator near the 50 Hz noise source--such as inside an HVAC duct, etc.
Chris
https://www.ekustik.eu/catalog/woody-resonator
There are Helmholtz calculators on the web that you can use to help you design your own, such as:
https://www.omnicalculator.com/physics/helmholtz-resonator
http://www.acousticmodelling.com/helmholtz.php
https://www.calctool.org/waves/helmholtz-resonator
An old diyAudio thread:
https://www.diyaudio.com/community/threads/helmholtz-resonator-inside-a-sealed-cabinet.219863/
I'd also recommend looking at placing a resonator near the 50 Hz noise source--such as inside an HVAC duct, etc.
Chris
One thing that should be pointed out: there could be harmonics of 50 Hz (i.e., 100, 150, 200 Hz, etc.) that are present with your HVAC system.
I recommend taking an acoustic measurement with something that can do a spectral analysis, perhaps using some inexpensive phone app (or something like that), to verify that you've only got 50 Hz present. You may have to design your Helmholtz resonator setup for more than one frequency.
Chris
I recommend taking an acoustic measurement with something that can do a spectral analysis, perhaps using some inexpensive phone app (or something like that), to verify that you've only got 50 Hz present. You may have to design your Helmholtz resonator setup for more than one frequency.
Chris
Hi
Thanks
i think i will put such helmholtz resonators in the corners and behind my me. But would a heavy cloud panel also do something? A free swinging weight from the ceiling with 50Hz resonance and Rockwool on the top?
The sound comes definetely only from the compressor motor outside.
It's a steady 50Hz signal meassured with spectroid on the source and inside the room.
The compressor gets cooled by the suction gas and have hot gas on the high pressure side at a certain temperature so I think it would be OK if you put acoustic dampening around the compressor inside the cabinet. You be the judge if something else might be effected, but the working conditions of the compressor will not change much.
Some part of the suction side of the compressor can be and probably will be covered in frost or ice when run for some time.
Don't put dampening on the parts that are iced or frosty because that can build a ice block.
@geoffkait:
Seems to be mechanical vibration from the compressor and not a humming transformer. That could be solved with a DC blocker.
Some part of the suction side of the compressor can be and probably will be covered in frost or ice when run for some time.
Don't put dampening on the parts that are iced or frosty because that can build a ice block.
@geoffkait:
Seems to be mechanical vibration from the compressor and not a humming transformer. That could be solved with a DC blocker.
Last edited: