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"Fan Mufflers"
SUMMARY: An effective way to muffle some noise, but not all.
The good guys at Muffled Computing were nice enough to send samples of their fan mufflers to test out. These are not cheapo plastic products:
They are made of steel lined with sound absorbing foam. The mufflers ship with velcro strips which are used to mount the muffler on the PC. Looking in the back of the muffler,
you can see the baffle arrangement - some sound is absorbed by the foam, yielding a perceived reduction in sound levels. This diagram shows
the baffle arrangement - the red arrows represent sound while the large blue arrows represents airflow. If you look straight into the front of the muffler,
you won't see any "daylight" - this is what traps the sound; looking into the back,
you can see the bottom piece which is placed directly in front of the exhaust fan. The velcro strips run almost the full length of the muffler - securing it to the PC should not be a problem.
Muffled Computing has three models - one for the power supply, one for exhaust fans and one for a front intake fan. All are of the same design and work with 80 mm fans; the model for a front intake fan, however, requires mounting inside the case. Details and examples are available HERE.
I tested the Power Supply Muffler with two power supplies: A Powerman 300 watt unit, model #FSP300-60BT. This is an older unit with one fairly loud exhaust fan. The second one I used was a PC Power and Cooling Silent 275 watt ATX. This unit is already very quiet, and I think is representative of some newer units on the market which feature low speed fan controls.
I tested the muffler with a Radio Shack sound meter. I placed the meter at a 45 degree angle from the exhaust fan, parallel to the center of the fan. To get readings, I had to place the meter 6" from the Powerman's fan and a whopping 2" from the Silent 275 (it IS quiet). I found the following:
These are substantial differences. The best way I can describe the muffler's effect is that it sounded like the power supply was in a tunnel - muted and a noticeable decrease in high pitched tones. It lowered the pitch such that the noise was distinctly lower in tone, adding to the perception of noise reduction.
On an already quiet power supply, such as the Silent 275, noise was so reduced that it was barely audible three feet away in a quiet room. With any kind of background "white noise", a quiet power supply with the muffler will be inaudible.
The power supply muffler significantly reduces noise, but not all noise. If you have a noisy heatsink fan, the muffler may absorb some of its sound, but most likely not enough to make a difference. The muffler works very well on a direct sound source, but an un-muffled heatsink fan will still be loud. If the loudest sound on your PC is the power supply's exhaust fan, this muffler can help.
Thanks again to Muffled Computing for sending this our way.
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