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Controlling tha Noise?
Quite a few submitters have asked "How do you make a quiet PC". Well, rather than tackle it from the PC standpoint, how about devices that
can quiet a whole environment? Along these lines, 16977 asks: "I've been considering building an active noise control system for an area about the size of a closet. ANC today doesn't work quite as well as it did in Silence, Please (works best for low frequencies, only covers small areas, etc.), but it is still a fascinating technology. I'm wondering if anyone out there has done similar projects with either the hardware or controlling software of ANC, and what information they have to share." And since I have your attention on this subject, sammy.lost-angel.com asks: "I would like to ask the slashdot community about their recommendations for noise-cancelling headphones. Traveling in planes is very noisy, and with MP3 players becoming more and more common, I would like to hear some experiences with various different noise cancelling headphones paired up with MP3 players. How well do they work in general? What is the best and most cost-effective headphones available?"
Headwise has a DIY noise-canceling headphone project. That's probably the most cost effective way to get a pair.
fnord
In my experience, they do provide a noticable drop in background noise on a plane. But I didn't find it enough.
Quiet-ish noise is better than loud noise - but don't spend $80 (I think that's what I spent) expecting silence.
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Oregon
Granted, this is a bit out of the price range most people are willing to pay, and are overkill if you just want headphones, but the Lightspeed 25K ANR aviation headset is fantastic.
I tried it once in my cubicle (inside a large IBM mainframe style machine room with a couple of rackfulls of machines and 4 large air conditioners) and it almost completely silenced the ambient noise.
Keep in mind, these headsets are around 20-28dD passive, plus another 23-30 dB active noice cancellation, but they are designed around the frequencies put out by 4 cylinder piston airplane engines at around 2400 RPM.
I believe Bose X headsets are similar. I don't know if their non-aviation headsets are anywhere near as good those.
BTW, The 25K's typically go for around $450-$500.
Electronics Now (more recently named Poptronics) published a cover article on this very subject. It's in the September '97 issue. I'm quite certain you could find it at any library that carries magazines - our local public library doesn't destroy magazines until they're 5 years old, so you might be in luck if your public library has a similar policy.
The project is a very simple one. Microphones are mounted (with epoxy?) on the outside of the headphones, and their cable runs down along with the headphone cable. The control box has a phase adjustment knob that allows you to adjust for the distance between the microphone and speaker elements for maximum effectiveness.
I haven't built the project myself, but if you have enough of an interest in electronics, you can build it yourself quite easily with parts from the local Radio Shack.
grey wolf
LET FORTRAN DIE!
because you can never place the noise cancelation generator at the exact same place as the noise source, you will always end up with places where the noise caceling device makes the noise twice as loud. Two rocks droped in a pond create waves. some times the waves are equil amplitude and frequency but opposite polarity and cancel eachother. Other times the waves are equil frequency and aplitude but their polarity is the same. The interfearance pattern created is the basis of active noise cancelation. But since you can never get the pattern to line up perfectly, the effectiveness of noise cancelation for general white noise is horrible.
Better to dampen the source as well as possible. Liberal use of sorbothane is extremley efective in reducing noise in a computer. shock mount every fan, the motorboard, power supply, cd drive and hard drive on sorbothane risers. Use nylon screws through the sorbothane spacers with sorbothane washers. Line the inside of your case with anechoic (egg crate) foam. Bigger fans turning at lower rpm are preferable. Centrifugal fans tend to be quieter when moving a given amount of air than radial (standard) fans. 36x is about the fastest CD drive you can get that will not induce horible vibrations in addition to their noise component. fan filters made of nylon stockings reduce fan noise considerably while standard chrome fan grills actually add to the noise a fan creates.
My computer is relativly quiet (56db 12 inches from the air intake) while still moving air at 700 cfm through the case for cooling. I used 48 volt centrifugal furnace fans on sorbothane shock mounts to acomplish this.
If voting were effective, it would be illegal by now.
I've used Sony's MDR-NC20 model headphones with no problems for almost 2 years now. They make computer labs on campus much much quieter, and allow you to listen to music at a quieter volume. They do the same in airplanes, although I've only been up with them twice. Even if only to quiet the noise (without music), they're still valuable.
I have a set of these headphones... they work very well. They do exactly as your brother describes; cancel out engine noise but still allow you to hear other things. They will always accompany me on a flight; after using these you just can't go back to regular headphones.
However, I had to return mine (to Best Buy) twice because the first two pairs had problems with noise reduction only working one side.
sudo eat my shorts
I've owned all three headphones, and currently use the Bose. Here are my impressions:
Aiwa (I don't remember the mode), ~$50:
- OK sound quality
- OK noise reduction
- Not-so-good comfort
Sennheiser HDC-451, ~$150:
- Good sound quality
- Good noise reduction
- Not-so-good comfort
Bose QuietComfort, $300:
- Excellent sound quality
- Good noise reduction
- Excellent comfort
The problem I had with the Aiwas and the Senns is that the earpieces sit against your ear lobes like regular open-air headphones, and after a while it becomes uncomfortable. They have thin earpads that don't offer much padding - I assume to keep noise from leaking through. The Bose set has earcups that surround your ears and sit against your head, and have a soft padding material on them. I've worn these on 5-hour flights and they don't bother me at all. The Bose also have the best sound quality, though the noise reduction doesn't seem to be any better than the Senns.
You might also want to look into Etymotic ER-4 or ER-6 headphones. These are little earbuds that seal out ambient noise (Etymotic advertises 20-25 dB passive noise reduction on the ER-4s). The ER-4s are spendy ($250-300) but the ER-6s are cheaper ($125-150). I tried a similar thing from Koss called "The Plug" but they sucked. They used a foam earplug-type material surrounding the driver on each side. The foam wasn't dense enough to seal well and it didn't hold its shape. Complete waste of time & money IMHO.