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Controlling tha Noise? 60

Posted by Cliff from the s/Controlling/Bring/ dept.
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?"
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Controlling tha Noise? More

Controlling tha Noise?

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  • Could you clarify whether you are trying to make the inside of the "closet" quiet, or trying to prevent noise
    from escaping the closet. They are two very different problems. The solution for preventing noise from
    escaping the closet is so straight forward that I can't imagine why you'd need to ask here. ( look into
    recording booth construction ). Why you would want to solve the second problem makes no sense at all.
    • The problem with not being able to prevent noise from escaping is answered in your post: look into recording booth construction . Some people are not able to make serious modifications like that, if, for instance they live in an apartment / college or military dorm, etc. Placing a noice cancellation device in the closet is the best answer for that situation.

  • Cost Effective Noise-Canceling Headphones (DIY) (Score:5, Informative)

    by Mr.Mustard ( 58247 ) on Sunday February 10, 2002 @06:25PM (#2983842) Homepage
    Headwise [headwise.com] has a DIY noise-canceling headphone project [headwize.com]. That's probably the most cost effective way to get a pair.
    • I followed the HeadWize project, but couldn't quite get the phase cancellation right; it was good to burn my fingers on the soldering iron again :-)

      I tried Brookstone's NC headphones, found them to be OK but not very comfortable; I eventually splashed the $300 on the Bose QuietComfort [bose.com] and haven't looked back. They are fantastic, thoroughly recommended.

  • Worse and worse (Score:1, Insightful)

    by Anonymous Coward
    Controlling tha Noise

    Did you mean 'the'?

    A three letter word in the title is spelt incorrectly ... if so-called editors let this past then there is no hope left for them.

    (EOE!)
    • Notice what department this article is from. Now google for "Public Enemy" and see what one of their biggest tracks is.

      I think that it was a really stretched attempt at humor, much like Emily Dickinson's poetry is a stretch at rhyming. It works, but it's kind of like hammering nails with a 9.1 Seagate Elite.

  • 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.
    • > In my experience, they do provide a noticable drop in background noise on a plane. But I didn't find it enough.

      And you've brought a box full of homebrewed electronic components onto an airplane after 9/11?

      What did the security drones say? (Seriously -- I've got homebuilt computer/audio gear and test equipment that I'd like to bring with me while traveling, but am worried about ever seeing it again because some jerkwad getting $5.00/hour thinks it's a bomb or weapon. Or worse, after I demonstrate it to him, said jerkwad says "Cool, I always wanted a pair of noise-cancelling Sennheisers!" and confiscates 'em anyways.)

  • Noise cancelling headsets... (Score:5, Informative)

    by nneul ( 8033 ) <nneul@neulinger.org> on Sunday February 10, 2002 @06:44PM (#2983920) Homepage
    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.
    • 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.

      BTW, The 25K's typically go for around $450-$500.

      Sony makes a low-end version of these which are enough to cancel out air conditioning and case noises, and which have a standard headphone jack so you can plug in and listen to PC music while working.

      You should be able to find them at Best Buy and similar for only $60.

  • Noise-Cancelling headphones (Score:4, Informative)

    by the_greywolf ( 311406 ) on Sunday February 10, 2002 @07:18PM (#2984051) Homepage
    Electronics Now [poptronics.com] (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.
    • 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.

      Or go to your local Best Buy or similar and pick up a pair of these [sony.com] for about $60.

  • active noise cancelation (Score:5, Informative)

    by Perdo ( 151843 ) on Sunday February 10, 2002 @07:34PM (#2984114) Homepage Journal
    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.

    • 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.

      In a word, no. You neglected to note that you can have a sensor involved. Active noise cancellation involves having a microphone to pick up the signal, a bit of circuitry to adjust the phase (varying by frequency, to allow for the physical separation between the mike and the speaker), and a speaker to emit the cancellation signal. The relative position of the source doesn't matter at all. What does matter is the periodicity of the signal. True noise is hard to cancel, especially at high frequencies. Periodic signals and low-frequency random signals are quite easy to handle.

      • Re:active noise cancelation (Score:4, Funny)

        by one-egg ( 67570 ) <geoff@cs.hmc.edu> on Monday February 11, 2002 @03:09AM (#2985581) Homepage
        There was a review of noise-cancelling headphones in the LA Times a year or two ago. Somewhat unsurprisingly, the expensive ones worked better. But the most interesting comment in the story was a social one: on airplanes, everybody talks louder than normal. With the 'phones on, the writer could clearly hear conversations 3 rows back. He found it annoying -- but not nearly as annoying as the guy just behind him who hummed "Do you know the way to San Jose" over and over throughout the flight. Without the 'phones, he was inaudible, and I'm sure he had no idea anybody could hear him. Drove the writer nuts.
    • Your statement is true only for two point sources and infinite space. If you have many speakers enclosed in a room, you can do a lot better. The real limit here is causality and predictability, not sources.
  • "I would like to hear some experiences with various different noise cancelling headphones paired up with MP3 players."

    Just dont start singing out loud!

  • I can see it now (Score:2, Insightful)

    by isorox ( 205688 )
    You kick back with your noise cancelling headphones on with your eyes closed, or maybe reading a book. In the next Isle a guy starts setting fire to his shoes, while just infront of you 5 blokes get a couple of knives out.

    Remember to keep some awareness of what is going on around you - turbulence warning etc.

  • Sony MDR-NC20 Headphones (Score:2, Informative)

    by psidon ( 26043 )
    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.

    • Agreed. I use them in computer labs as well (though I haven't tried taking them into the loud mainframe machine room at work). There are a few problems with them:

      • If you turn them on without any input signal (computer, MP3 player, etc), you hear some static. This goes away as soon as you turn on your music.
      • When there is a sharp noise (e.g. someone smacking a computer), the headphones amplify the sound and echo it several times.
      • They perfectly cancel out one really annoying guy's voice. Lips move, no sound. :-)
      • I can hear most other voices perfectly, but almost no computer fans. The screeching sparc hard drives are out of this unit's range

      Random question: does anyone know what type of plug/cord goes on the bottom half of these things? The extension cord is beginning to become separarated from its plug and I'd like to get a new one, but I don't know what it's called!

    • If you like those, you should see the MCDR-NC10 set. I picked up a pair several months ago, and they've preserved my sanity very well. I fly fairly often, and find them to be invaluable.
      There's a review [audioreview.com] of them here, and it's pretty much right on. I highly recommend them. They're very comfortable over long periods, and when feeding audio, you pretty much lose all external audio inputs.

      The single thing about them that bugs me is the connector cable. There's a detachable connector from the battery unit which has the headphone jack connector on one end, and an obviously proprietary connector on the other. Losing this cable would be a big pain in the ass. I would guess they have other connectors for different interface types, but it'd be nice if it was a standard conversion I could hit Radio Shack to replace.
  • The biggest source of noise in my new machine is the heatsink fan. I would love to merely quiet that one fan, but I can't think of any sane ideas to do so. Anybody had success getting those suckers to be less noisy?
  • I got my brother some AIWA [aiwa.com] headphones at Fry's for about $50, he's used them on several plane flights and says that he can no longer hear the engines, but can still hear the flight attendants when they ask what beverage he'd like.

    Don't know if you're trying to get rid of all sound, but they do a pretty good job of reducing backgroud noise. He's sworn he's never going back to non-noise cancelling headphones.
    • 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.

  • Bose QuietComfort (Score:2, Interesting)

    by rdfager ( 72392 )
    I travel almost constantly and have tried Bose and Sony noise cancelling headphones. I recomend the Bose. They are quite a bit more money but in my opinion are well worth it. I don't leave home without them.
  • 1. Low cost ANR headphones (that are basically microphones playing back the ambient noise out of phase through Walkman headphones) aren't that useful for office-type noise. They're fairly useful on airliners, where there's a LOT of low-frequency rumble they can remove, and fairly quiet at mid frequencies.

    2. Expensive aviation-type ANR headphones (someone posted links) are better than the low cost ones but you still shouldn't expect any miracles. There's no substitute for an actual quiet environment.

    3. For quieting down your closet, check the products and info pages at soundproofing.org [soundproofing.org]. Despite its .org domain it appears to be a regular commercial outfit, and the website design is not so great, but the stuff there looks pretty good.

  • It's almost always easiest to control noise as CLOSE to the source as possible - aka, prefent the noise from being created in the first place, or else muffle it right away

    As for the headphones, I have a pair of Sennheiser HD-451s that work great - makes flying reasonable, and they sound good too
  • Not to come across as a jerk, but for noise canceling headphones, I know that they work by creating an equal but opposite soundwave to essentualy cancle out the original noise. Why not look at using small ear-bud type headphones and (dispite looking like a freak) put on a pair of earmuffs like you use at a gun range. Some of the better ones (like Peletor) drop the noise by almost 30 db, which is 1/8 the original sound.

    As for the sound proof closet, bad sceens from movied pop into my mind, but There are a few options, but all of them make it harder to keep the room cool if you have a half dozen computers in it. I know most THX certified movie theaters have a quick solution durring building them. Instead of one layer of sheet rock/drywall per each side of the stud, they use three per side. Gets spendy, but you when isolating 120 db from one theater and the ones next door, it works. Non smooth walls help too, like carpet, here again look at a movie theater wall. Heavy/thick drapes could also be installed or hung. I just thought of possibly building a cover box out of say two or three layers of sheet rock, adding a ventalation system to it, and putting it over the loud machine(s) in question. Imagine a cardbord box that is just put over the top of the computer, only it's two layers of sheet rock, 2x4's and a door with a hindge. Think of the old printer alcoves that were for the old dot matrix printers. They were lined with foam fingers to absorb the noise.

    Also, there are a lot of low noise computer fans now available, and ways that you can silence the hardware, by adding weight to a noise producer like a hard drive. If you bold on a chunck of aluminum to a hard drive, you can change the vibration frequency on it, changing the pitch you hear, and possibly force it to an extreme you cannot hear.

  • Headphones - Aiwa vs. Sennheiser vs. Bose (Score:3, Informative)

    by mcmasuda ( 126879 ) on Monday February 11, 2002 @02:16PM (#2987979)
    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 [etymotic.com] 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.
    • Sounds like my experience...

      I, too, went for the spendy bose headphones as a last resort. They work great. My only complaints: because these are rather well sealed units, after a while my ears get sweaty (but they are still very comfortable). Also, the external amplifier/battery box is cumbersome -- it sometimes falls off my desk, yanking the cord to my head.

      With the bose, some noise still gets through, but I'm always amazed when I take them off how loud my computer really is. The sound quality is good, but the amplifier injecting noise (as it is designed to do!), I don't think any noise canceling headphones can compete with a decent pair of studio-type headphones and a quiet room.

      I also tried two Sony headphones from crutchfield [crutchfield.com]:
      MDR-NC5, $99 - Not a closed-ear type, so the noise reduction wasn't that great.
      MDR-NC20, $150 - This has a closed construction, but the noise reduction didn't seem to work too well - the headphones added quite a bit of their own white noise.
  • Try this. Line the room with hundreds (thousands?) of styrofoam cones, so that the walls look something like this:
    >
    >
    >
    >
    (that is just one wall, stupid lameness filter)
    The cones will absorb all sorts of wavelenths, and make the room really quiet. I've been in rooms like this before, and there is almost zero reverb no matter how loudly you yell or how much noise you make.
  • I'm getting really sick of the notion on slashdot that everything can be both cheap and perform spectacularly.

    Here's a template for all you ask-slashdotters out there:

    A Clueless Slashdroid [cheapassbastard.com] asks: "I've recently become interested in performing Action X. So far, the best way I've found to do this is to purchase Product Y. I know Product Y costs $Z, but I'd like to know if there is some other product W out there that performs Action X as well as (or better than!) Product Y for cost $Z/3 or less. Is there a cheaper, do-it-yourself Method M that will perform just as well as either of these products? Can I do any of this with duct tape, bailing wire, and Open-Source Software ?

    Any help would be appreciated, as I am too lame to do my own research!

    - A.P.
    • I'm getting really sick of the notion on slashdot that everything can be both cheap and perform spectacularly

      Eh? Excuse me, but "cheap" and "cost-effective" are not the same...they're almost opposites. "Cheap" to me means "spend the least amount of money possible, usually sacrificing quality."

      "Cost-effective," on the other hand... well, I can't think of how to shorten it into a similar quip (it's 3:30am, gimme a break). But to me, that means getting the best price/performance ratio. There does exist a point where purchasing a higher quality just doesn't matter, because the differences can't be heard or felt. So in this situation, the "cost effective" solution would be not what's cheapest, and not necessarily the highest quality on the market, but rather the solution that gets the job done for the least amount of money.

      Cost-effectiveness is a good thing.


  • Whenever ambient noise starts getting on my nerves I put on The Who's Live at Leeds [addict.com] and listen to it at a naturalistic 130 db. By the time it's over, the background noise has faded almost to inaudibility. Just a bit of a ringing sensation, and that's about it. Like, you can hardly even hear the landlord pounding on the door.

  • If by traveling in planes, you mean flying in prop planes, helicopters, anything where you are plugging into the plane systems, etc, then what you want is a set of David Clarks. Industry standard since sometime around World War II, watch a movie or TV show. If the pilot is wearing a light green headset, they are david clarks. I occaisonaly wear mine here in the server room at work, when the noise gets to me, and the room just goes silent. The only problem is it looks a bit odd. This reminds me--does anyone out there have a good set of plans to convert military style aviation headsets to general aviation? (I know about the adaptor that is available, it costs more than these headsets do).
    Note: General aviation headsets will work with standard stereo and computer equipment, and can be had at relativly low costs, and the sound that comes out is unbelievable in quality, compared to any thing else that I personally have experienced

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