BYU Project to Silence Computer Fans 369
phunster writes "The New York Times has an article about Scott D. Sommerfeldt and his students at BYU who have created a noise suppression system for computer fans (drop of human blood required to read article). The technology is not new, he uses out of phase sound to substantially cancel out the sound of the fan. What is interesting is his implementation of the technique. While other systems place a microphone and speakers in the center of a room, he places four miniature speakers and microphones around the noise source itself. His results are promising."
NY Times Random Generator (Score:2, Informative)
Not when you use this [majcher.com]
Just wear NR headphones (Score:3, Informative)
No-reg link (Score:5, Informative)
http://www.nytimes.com/2004/05/27/technology/circu its/27next.html?ex=1086235200&en=8355c13a3b4a8afa& ei=5062&source=GOOGLE [nytimes.com]
Re:Silent fans are a BAD thing (Score:4, Informative)
If my CPU fan stops spinning my computer throws a tantrum you can hear from space.
Text from article... (Score:2, Informative)
By ANNE EISENBERG
Published: May 27, 2004
THE constant drone of a computer cooling fan can be annoying. But a professor at Brigham Young University has taken an unusual step to mute this noise: more noise, produced in just the right quantities from tiny loudspeakers that surround the fan.
"We make anti-noise," said Scott D. Sommerfeldt, a physicist who created a noise suppression system with his students. It is the latest example of a technology called active noise reduction, or noise cancellation, well known from its use in headphones designed to block out the low rumble of jet engines.
The sound waves engineered by Dr. Sommerfeldt are out of phase with sound waves from the fan and thus they cancel each other out, substantially reducing fan noise.
Dr. Sommerfeldt's system has four miniature speakers and four even tinier microphones set in a ring around the computer fan. The microphones and other sensors detect the noise of the fan blades and, with the help of digital signal processing and algorithms, radiate opposing tones from the speakers. The whole system can be tucked into the same space that a conventional computer cooling fan would occupy.
Noise-cancellation technology has been in development for more than 50 years, Dr. Sommerfeldt said. In typical headphones, microphones in the headset detect noise; the speakers in the earcups counter with anti-noise.
Dr. Sommerfeldt's target was not the roar of aircraft, but the hum of office machinery. To counter this noise, some active noise reduction systems place microphones and related gear in the middle of a room to calculate the amount of cancellation needed.
But Dr. Sommerfeldt wanted to put the system within the computer casing itself so that it might one day become a built-in feature of personal computers.
Trying to cancel noise from within the computer turned out to be tricky, though. "You are asking for trouble if you place the mikes right next to the fan," he said. While it may be possible to reduce the sound substantially at the microphone, he said, the noise level could increase farther away, where someone might be sitting.
To solve the problem, Dr. Sommerfeldt built an aluminum enclosure that mimicked a typical computer chassis and put a standard cooling fan within. He and his students placed microphones and speakers around the fan, analyzing the nature of the sounds they would have to suppress and modeling systems to counter this sound.
"The fan is not an easy source of noise to control," said Gerald C. Lauchle, a professor of acoustics at Pennsylvania State University and a colleague of Dr. Sommerfeldt. "Many interacting mechanisms create the noise."
The specific sounds Dr. Sommerfeldt decided to counter were those made by the blades of the fan as they rotate and push air past obstructions like fan supports. The pushing is periodic, dictated by the number and speed of the blades.
In the experiments, sensors mounted near the blades of the fan recorded the motion, and the information was fed to the digital signal processor along with the data from the microphones that were monitoring the overall noise. Then algorithms developed by the group adjusted the amount of canceling sound waves sent to the speakers so that the basic tone of the blades could be suppressed, as well as overtones or harmonics of the basic tone.
"The basic tone is distinct," Dr. Sommerfeldt said. "It sounds like one you could hear if you hit a piano key."
To find the pattern that worked best, the experimenters set up systems with one, two, three and four speakers. "We went with smaller loudspeakers and more of them," Dr. Sommerfeldt said. "The best configuration turned out to be four speakers spaced around the fan."
The group measured the reduction in sound at the fan and at various points at a distance, said Brian B. Monson, a graduate student of Dr. Sommerfeldt.
The experiments used two fan sizes, with b
Maybe its not the fan. Keep the Horse in front!! (Score:5, Informative)
Maybe we should look at the fan design first. When Brushless-DC fans were first introduced in the early 1980's I evaluated most of the major brands. Blade shape and contour were major contributors to noise, but by far the worst was mounting the fan up against the panel wall with holes or a grill. Running slow also reduces noise. One company's blade design removed the high pitch wind noise and just left a low pitch rumble that sounded quieter than it was. Centrifugal "squirrel-cage" fans were much quieter than axial fans. Sleeve bearings were a little quieter than ball bearings, but had a much shorter life and will "freeze-up" once the oil dissipates. (I actually had this happen to my old computer.)Ball bearings get louder over time, but you'll replace your computer before then.
Power supplies can reduce airflow requirements considerably by better heatsinks and/or using the chassis for moving the heat away from the hot components. Once the real design issues are tackled, the bell-and-whistles approach could then be used to further reduce sound levels as necessary.
Dell mounts one fan deep inside the computer and the PS fan is quiet but near a wall. Six weeks ago I bought a Systemax and a Dell computer. Systemax sounded normally obnoxiously loud. Dell was so quiet, I thought it was not working, so I opened it to see if I could tell what was wrong. I was fooled by the sudden start of noise and then quiet.
Re:No-reg link (Score:1, Informative)
simpler alternative (Score:2, Informative)
Re:No-reg link (Score:2, Informative)
Or you can try http://newsnet.byu.edu/story.cfm/49321
Re:Next project... (Score:2, Informative)
As for your assertion that the majority of Americans have a negative opinions of Mormons, I take issue with that. (And no, I don't think its Satan's fault.) However, from my experiences with people outside the church, many have had very good views of me and my church. And no, I haven't lived in Utah my whole life. (Quite honestly, I detest Utah...) I grew up majoritaly in the Northern VA/Washington DC area... probably the most diverse collection of people outside of New York or Boston. Yeah, I'm definitely considered different and akward by a good majority of my friends, but they respect that and me just the same. Give me some hard numbers from an independent source, and I might give a second thought to that, but from my experience, people have been rather respectful of me and my religion.
As to side note that, whether people accept something has never been a standard by which something should be judge.
I'm truly sad you've only had negative occurences with my religion or people in it, or that you have formed this view on your own. I doubt there's much I can say to change your mind. All I know is its a gospel based on Christ and love and I hope you can recognize that.