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Sound cancellation technology?

Discussion in 'Misc Electronics' started by Voice of freedom, Apr 5, 2005.

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  1. How far has sound cancellation technology come, for use in a room area? For
    example, for a bedroom?

    I need some sound cancellation in the bedroom due to street noises outside
    while I'm trying to sleep.

    I know they have it inside closed headsets for pilots etc, but is the
    technology viable yet for a closed room sized area like a bedroom?
  2. Luhan Monat

    Luhan Monat Guest

    No, and (for all practical purposes) it never will be. Headphone
    devices 'muffle' the higher frequecies while 'cancelling' the lower
    ones. But this only works with headphones.
  3. Voice of freedom wrote:


    I have the answer you seek, , but I don't answer questions
    that are posted to the wrong places. You posted to:

    ..misc newsgroups are for posts that don't fit anyehere else.
    This post does fit somewhere else, so it shouldn't be posted
    to sci.electronics.misc.
    Possibly OK, depending on what you are asking for. If you
    want an existing piece of equipment, your post belongs in but not in
    If you want to design something or have something designed,
    your post belongs in but not in

    ..marketplace newsgroups are for posts advertising things for
    sale. You aren't selling anything, so you post does not belong
    in misc.industry.electronics.marketplace
    Possibly OK, depending on what you are asking for. If you
    want an existing piece of equipment, your post belongs in but not in
    If you want to design something or have something designed,
    your post belongs in but not in
  4. That is the original idea. But I have heard that it works even better
    to put the reference mic inside the headphone, and apply negative
    feedback to make the sound inside follow the sound you want, whether it
    is music or silence.

    That way it doesn't matter what the outside noise is, everything which
    is not exactly the wanted sound is cancelled.

    Simply apply negative feedback from the mic to make sure that the sound
    inside is exactly silence, that will automatically cancel any
    disturbancies, whether electronic or acoustic in origin. It is similar
    to the motion feedback system Philips used in loudspeakers once. It
    forces the sound in front of the loudspeaker to be an exact copy of the
    sound signal you want, or silence if that is the result you want.

    Talking about the problem in general terms and in rooms also:

    You need a passiv screen between the ear and the noise, which dampens
    the treble sounds and makes it a lot easier to apply electronic noise
    cancelling. In a room this screen can be the walls, in a headphone this
    screen is the outer plastic material. Heavy cloth materials dampen
    sound well.

    The problem is more difficult in a room or apartment, if you want to
    cancel noise no matter where you are in the room.
    It is easier to cancel noise electronically for a listener in a certain
    position in the room.

    In a room it can be enough to play some own music, to avoid total
    silence, which make the ears more sensible for occasional noise from
  5. René

    René Guest

    I use earplugs with great succes..
  6. Ray L. Volts

    Ray L. Volts Guest

    Simpler, more effective, and most importantly, currently available:
  7. Please, I'd like some refferences on that. The tests I've conducted (two
    4" speakers 1kHz in a Y-shaped pipe) suggest that it can cancel _pretty_
    loud sounds. I don't know what signal level I ran at, but it was at
    least hearable 30m from the source. When I fed the speakers with
    opposite waveforms, they canceled out, and only a slight hum could be
    heard. I guess this hum was the vibrations in the mount for the speakers.
  8. Well, I can't see how not. If you manage to place them according to the
    noise, you should get the same effect, if using a DSP that calculates
    the waveform, and timing.
    Mercedes used this on some of their cars to cancel out noise, and many
    planes use it...
  9. Dave Fase

    Dave Fase Guest

    I sold and installed the Headsets, Inc. Active Noise Reduction (ANR) kits to
    pilots for a while back in the mid nineties. Kept up with the advances back
    then. If I recall correctly, Bose Laboratories in Boston was experimenting
    with "whole aircraft cabin" ANR systems, and that some Business Aircraft
    manufacturers were offering Bose's ANR option to anyone who could afford it.
    The option was expensive, requiring a number of well placed speakers, a fair
    amount of electronics, and extracting some useful load. For reference,
    to indices of the SAE publication "Aerospace" from the mid to late nineties.
    I think I also recall that someone was building similar ANR systems for OTR

    Recollections aside, in my opinion, ANR equipped headsets were, and are a
    real plus while flying in general aviation aircraft. Most systems I tried
    cancelled much of the lower frequency engine and exhaust noise, and certain
    components of slipstream noise. The design and shell of the headset earcups
    knock down much of the higher frequency components. All of which makes
    for a more relaxing, less tensing flight. A bedroom sized system might work
    similarly well for lower frequencies, but I doubt there would be much
    protection from higher frequency components such as sirens, plant whistles,
    and the like. Just like the earcup shells on a headset, one would probably
    to super-insulate the walls of the bedroom. One problem which was dominant
    with all systems was a "hiss", almost like "white noise". This could be a
    problem on a room or cabin sized ANR system.

    Hope that helps to answer the original question. Aloha, Dave
  10. Your name is Rube Goldberg?
  11. Yes, I've heard that some experimenters have come pretty close to being able
    to do very simple sound cancellation in a room area, without headphones, but
    not close enought to produce a perfect product to sell. High speed DSP was
  12. I already have double windows, which helps some, but the place across the
    street is running some kind of home shop business and fills up their
    dumpsters a couple of times a week, then calls for pickups. The garbage
    truck is a big diesel rumbling thing and that wakes me up, right through
    the walls etc.
  13. Clarence_A

    Clarence_A Guest

    "Voice of freedom" wrote
    Unless you sleep during the day, check the Noise abatement
    regulations and file a complaint.

    If you sleep during the day Move! It's cheaper.
  14. Ben Bradley

    Ben Bradley Guest

    misc.industry.electronics.marketplace and,
    The next technical step would be a "room within a room" which is of
    course a large cost in labor and building materials. It would need to
    be built on a floating floor, with the walls and ceiling built on top
    of it without touching the existing walls and ceiling. Read F. Alton
    Everest's "Master Handbook of Acoustics" if you consider doing this.

    Do as Clarence suggested and look for some local noise ordnances
    they might be violating, in addition to running a business in a
    residential area which might also go against some ordnance, but at
    least be a good neighbor, explain the problem to them and give them a
    chance to fix it before turning them in for anything.
  15. Don Taylor

    Don Taylor Guest


    One quick question, having tried three brands of noise cancelling
    headsets, all three seem to do a good job at reducing low frequency
    noise like the roar and rumble inside city busses, engine noise,
    etc. But that just brings out the conversations that would otherwise
    be buried by the roar.

    Strictly dealing with headsets for this question, is not also
    cancelling voice/music by design, by limitations of physics, by
    limitations of processing power, by limitations of battery power
    or by cost of components?

    On related notes, but not wanting to derail answers to my question,
    perhaps a decade ago I was sitting in a class where the prof claimed
    that he had direct knowledge that the Cadillac NorthStar was named
    NorthStar because N S recognized that they had built Noise Suppression
    and noise cancellation into this car line. I was interested in
    this and contacted Cadillac about this at the time. They responded
    that this was not the case. We never could resolve this contradiction.

    Since that time we have seen advertisements by the companies selling
    trucks to the public, describing how much work they put into making
    the sound of their trucks make it clear that the owner has really
    really large male equipment.
  16. Luhan Monat

    Luhan Monat Guest

    Try the active sleeping ingredient in Bacardi.
  17. Pooh Bear

    Pooh Bear Guest

    Basically undoable.

    Get extra glazing installed.

  18. Pooh Bear

    Pooh Bear Guest

    As a sound engineer amongst my various skills, please note you're talking out of
    your arse.

  19. Pooh Bear

    Pooh Bear Guest

    Considered triple glazing ?

    Increasing the thickness / weight of the glass is hugely effective too. My
    windows are single glazed but with 6mm laminatated glass. Made an astonishing
    difference over the old windows.
    If it's coming through the walls that's not good. What's your wall
    construction ?

  20. Pooh Bear

    Pooh Bear Guest

    It could only happen in the USA ! Lol ! Do they fit machine guns too on request ?

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