[3dem] question about acoustics

Steven Ludtke sludtke at bcm.edu
Tue Dec 10 07:34:25 PST 2013

It should be pretty obvious, but a "hissing" sound corresponds to frequencies up in the khz range. 160 hz is a low humming sound, roughly an E3 on the musical scale, and will have a wavelength of ~2m. Unfortunately this can make it a little harder to locate, for the same reason that it doesn't matter where you put a subwoofer in a room. If you have an iPhone or other i-device, there is a handy app called bs-spectrum, which will display a real-time audio spectrum from the phone's microphone (on the bottom). You could use this and walk around the room to try and better-localize the source of the sound. Physically resting the phone on any suspect devices should magnify the effect a lot, and help narrow it down. In this range, though, the two most likely suspects in my mind would be a fan in a piece of equipment or someone playing music in the room above you :^)

On Dec 10, 2013, at 9:07 AM, Qiu-Xing Jiang <Qiu-Xing.Jiang at UTSouthwestern.edu> wrote:

> Dear colleagues, 
> The new EM space built for our JEOL2200 has excess acoustic noise at 160 hZ, above spec (43dB at the same frequency) by 10 dB. There is clear hissing sound from the ceiling (three vents there). We have applied egg shell crates to all four walls and the air supply comes from the perforated tiles below the raised floor. We are looking into different solutions. Before we land on any, I am writing to seek some advice from those who have successfully dampened acoustic noise in different ways. Please offer your thoughts. Thanks. 
> Qiu-Xing 
> UT Southwestern Medical Center
> The future of medicine, today.
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Steven Ludtke, Ph.D.
Professor, Dept of Biochemistry and Mol. Biol.         (www.bcm.edu/biochem)
Co-Director National Center For Macromolecular Imaging        (ncmi.bcm.edu)
Co-Director CIBR Center                          (www.bcm.edu/research/cibr)
Baylor College of Medicine                             
sludtke at bcm.edu

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