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Science

One-Way Sound Walls Proven Possible 177

Posted by Soulskill
from the good-sound-walls-make-good-neighbors dept.
disco_tracy writes "Imagine a room where a band is playing. Neighbors can't hear the music, but if someone outside the room is talking, the musicians can hear it. The concept — a kind of one-way mirror for sound — seems imaginary, but two Italian scientists recently pushed this kind of sound manipulating technology closer to reality (abstract)."
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One-Way Sound Walls Proven Possible

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  • by xanthines-R-yummy (635710) on Friday May 06, 2011 @01:52PM (#36049872) Homepage Journal
    Sounds like a good use for interrogation rooms...
    • by nschubach (922175)

      Automotive as well... being able to hear sirens outside the car without broadcasting your Justin Bieber sirens to the rest of us. Nobody needs to hear that.

      • by sconeu (64226)

        This is NEEDED for automotive applications.

        The rest of us do NOT want to hear your 1200 watt bass line on whatever it is you're playing.

        If we wanted to hear it, we'd be listening to the same CD or station.

        And when you drive through my neighborhood and cause the windows in house to rattle.... don't get me started (I know.. .too late).

        • It's a pride thing. You may not want to hear it, but they *want* you to hear it. A way off announcing their cultural identity.
          • by sconeu (64226)

            Fuck their "Cultural Identity". I don't need my fucking house to shake when they drive by.

            • by jshackney (99735)

              I always wondered if it would be possible to build a huge parabolic acoustic "mirror" that could focus the energy of those 1200 watt bass systems back either to the glass or the eardrums of the driver causing aural devastation. How big would this parabola have to be to get the kind of energy that could do some real damage?

              • You wouldn't want a parabola - to reflect back to the point of origin, you'd want a sphere. It'd be impractical though, due to the impossibility of tracking a moving car. Remember they are at ground zero for every note, so the car is built for it and the driver willing to sacrifice his hearing.
              • I like the idea of using science to deal with this, but I think the xkcd approach [xkcd.com] might be more practical -- and more fun.

    • Re:Uses (Score:4, Insightful)

      by wiedzmin (1269816) on Friday May 06, 2011 @03:50PM (#36051158)
      Also submarines.
    • by Thing 1 (178996)
      Pa pa l'americano.
  • Really necessary? (Score:4, Insightful)

    by jspenguin1 (883588) <jspenguin@gmail.com> on Friday May 06, 2011 @01:53PM (#36049884) Homepage

    What's wrong with an ordinary soundproof wall with a microphone on one side and a speaker on the other?

    • by Conspiracy_Of_Doves (236787) on Friday May 06, 2011 @01:57PM (#36049934)

      Where would we be if people were happy with what they had? There's probably all kinds of situations, and even new inventions, that could use this that we can't even think of at the moment.

      • by Idbar (1034346)
        Well, if it's controllable it would be nice having it on car windows, or if it isolates certain frequencies, you could use those frequencies for emergency vehicles so some @$^!#$% people won't block their way.
      • by EdIII (1114411)

        Another poster already mentioned it, but it truly bears repeating. Having that car blasting out their music completely silenced but still able to hear a police siren.

        From the article, this is not limited to glass at all. In fact, the article does not even indicate that the material is translucent at any point either.

        Something else to consider. Take two of these and slap them together in a sandwich and you know have sound proofing to a fairly extraordinary level in something that is likely to be only a pe

      • by bug1 (96678)

        Yea, for example, what would you do during an extended power outage, with no batteries, solar, or handcrank ?

        That silly microphone/speaker idea wouldnt be any use then !

        I heard of a new invention too, a movable two way sound resistance wall, with optional visual transparency.

        They call them windows.

    • I don't expect that the scientists in question longed to solve the problem of the band that needs to play loud music but still hear the people outside. They probably did it for the science itself, which seems fascinating.
    • Easily found with a bug detector?
    • by Anonymous Coward

      What's wrong with an ordinary soundproof wall with a microphone on one side and a speaker on the other?

      That's like saying why do we need one way mirror when we can just build a wall and put a video camera on one side and a monitor on the other? I'm sure there will be cases when something like this would be useful.

    • Re:Really necessary? (Score:5, Interesting)

      by SQLGuru (980662) on Friday May 06, 2011 @02:28PM (#36050312) Journal

      This would be material based and not require additional power?

      It would be great for those baby-rooms they used to have in movie theaters. The people inside could hear the movie without the audience hearing the screaming kid.

    • by Kamiza Ikioi (893310) on Friday May 06, 2011 @02:35PM (#36050406) Homepage

      The same reason why a 1 way mirror is better in some applications than a video camera on one side of a wall with a monitor on the other.

      On possible use is in security. People can avoid cameras, and small unseen microphones are not directional. Airports, casinos, police stations, and other security heavy areas will certainly have a use.

      Imagine the CIA setting up a room for foreign dignitaries. The dignitaries sweep the room for bugs. But unknown to them, the floor of their room is a 1 way sound barrier, with agents sitting below with directional microphones pointed at the ceiling underneath each room.

      Imagine a submarine with a section of the vessel being a 1 way sound room where large microphones reside. All other walls are sound deadened except 1 outside wall. More equipment could sit there than any outside array of microphones, listening for enemy ships... but without an outside sonar signature, and without worrying about hearing internal noises.

      Even naturalists would love it. Imagine a retreat in a forrest where every outside wall was 1 way, making it sound like you weren't even in a building, but the animals were not disturbed by the sounds you make snapping pictures and talking.

      • by klui (457783)

        That's where the Cone of Silence is useful in situations like what you've described.

      • by X0563511 (793323)

        You're assuming the sound would remain directional, which may not be the case. Indeed, I would expect the sound to be projected perpendicular to the surface. ... and it will probably not be as general as you expect. It will be a long way (if at all) until it would look like anything other than what it was.

    • by Creepy (93888)

      That is done in studios currently, but I think the main downside it requires electricity and someone usually has to push a button to turn it on (in my experience). Not really sure how effective it would be in a studio, though, unless you want a lot of natural reverb. Incidentally, I used to have a room set up with sound absorbing tile for that exact reason, but that all got torn out in a remodel a few years ago (it was in really crappy condition, or in my wife's words, was "fuggly and has to go"). I actuall

      • by X0563511 (793323)

        Sounds like you need to tell your wife to STFU and let you have your hobbies. Unless hers are fair game for your shooting-down as well, that is.

        (of course, find a nicer way to say it)

      • by hedwards (940851)

        I'm not sure this would be of any use in a recording studio. Typically they use monitors, and it's not because of the wall. The reason for the sound proofing is because the audio engineer is more interested in what they've got on tape than what's actually being produced. Because ultimately that's what they're going to have available when they go to master the CDs, not the actual sound that's being produced.

        You really wouldn't want to turn it around either, because you don't want to have to find completely s

    • What's wrong with an ordinary soundproof wall with a microphone on one side and a speaker on the other?

      Yeah, we wouldn't want any improvements in sound-dampening technology.

    • by Idbar (1034346)
      That you still need a soundproof wall? So instead of paying for the soundproof wall AND the electronics (and subsequent batteries/electricity). You just pay for the wall?
  • Band... (Score:5, Funny)

    by Joce640k (829181) on Friday May 06, 2011 @01:56PM (#36049928) Homepage

    Imagine a room where a band is playing. Neighbors can't hear the music, but if someone outside the room is talking, the musicians can hear it.

    They can't be a very good band if they can hear somebody talking in the next room while they're playing...

    • Obligatory Spinal Tap http://www.youtube.com/watch?v=wscZhvj_lH4 [youtube.com]
    • by irishPete (21197)

      I am not sure quality and volume are necessarily equivalent. Actually, I can attest that I have heard quite a few very loud, yet horrendous bands on any given Monday night at the Rat. (if you recognize the club, you're probably old too...)

    • Not only that, but they've got the use case backwards. The proper way to set it up is so that everyone else hears the band, but the band can't hear any of the complaints from the neighbors banging on the walls and yelling at them.

    • Re:Band... (Score:5, Funny)

      by Abstrackt (609015) on Friday May 06, 2011 @03:12PM (#36050880)

      Imagine a room where a band is playing. Neighbors can't hear the music, but if someone outside the room is talking, the musicians can hear it.

      They can't be a very good band if they can hear somebody talking in the next room while they're playing...

      Do you have any idea how hard it is to find an amp for an air guitar?

    • by FauxReal (653820)
      <quote>

      <quote><p>Imagine a room where a band is playing. Neighbors can't hear the music, but if someone outside the room is talking, the musicians can hear it.</p></quote>

      <p>They can't be a very good band if they can hear somebody talking in the next room while they're playing...</p></quote>

      Maybe the drawback is it amplifies sounds on the other site... or you can only hear someone if they speak vuvuzela.
  • by Anonymous Coward

    - "You have a banana in your ear!"

    - "I'm sorry, what?"

    - "YOU HAVE A BANANA IN YOUR EAR!"

    - "I'm sorry, I can't hear you, you're on the wrong side of the wall!"

  • Although the acoustic technology remains theoretical, the researchers think that it can be built. Lepri cited optics, saying that nonlinear photonics is a well-developed field now.

    Couldn't i just sound proof a room, put a few microphones outside the room send the signal in to the room. Doing it passively is cool but there is no way it would be cheaper then some soundboard a microphone and a speaker.

  • by tripleevenfall (1990004) on Friday May 06, 2011 @02:08PM (#36050080)

    "Imagine a room where a band is playing. Neighbors can't hear the music, but if someone outside the room is talking, the musicians can hear it."

    How does this wall mean the musicians will hear the talking over their own music? Is there one-way sound air coming soon too?

    • Re:Huh? (Score:5, Funny)

      by Garble Snarky (715674) on Friday May 06, 2011 @02:17PM (#36050190)
      Time division multiplexing.
    • "Imagine a room where a band is playing. Neighbors can't hear the music, but if someone outside the room is talking, the musicians can hear it."

      How does this wall mean the musicians will hear the talking over their own music? Is there one-way sound air coming soon too?

      They're just trying to explain the concept in very simple terms. Read the abstract instead if you're going to be pedantic.

    • by hedwards (940851)

      There's that, but there's also the question of why that would be desirable anyways. I assumed that meant between sets, but even that doesn't seem particularly useful. If you've genuinely blocked the sound from penetrating in that direction the people on the other side of the wall shouldn't have anything relevant to say.

  • Harry Potter did that, like, five years ago!
  • by Garble Snarky (715674) on Friday May 06, 2011 @02:21PM (#36050234)
    The article describes the proposed theoretical mechanism as a "wave diode" - I wonder if the same principle is applicable to light? I don't know if "light diodes" already exist in some sense, but that seems like a possibly useful component for optical computing...?
    • by kmac06 (608921)
      There is such a thing for light, an optical (or Faraday) isolator [wikipedia.org], which uses the Faraday effect. It relies on the fact that light is a transverse wave, not longitudinal, so it wouldn't work for sound. Note that because of the large magnetic field required, most optical isolators only have an aperture of a few millimeters (or less), so it would be impractical to build a "one-way" mirror of appreciable size out of it.
  • Ever since I was a kid I've dreamed of having a hot/cold pad. It only lets heat go through it one way, cold side painted blue, hot side painted red. Put it around your soda or beer can blue side in, it cools off your drink, remove when it's just right. Put it around your coffee or soup red side in, it heats it up.

    It would probably need a special holding case otherwise your backpack would catch on fire while carrying it. :-)

    • by adonoman (624929)
      You just need a really tiny man [wikipedia.org] to sift through the molecules and sort them by energy level.
    • Re: (Score:3, Informative)

      by operagost (62405)
      I'm not sure what this had to do with sound, but what you're thinking of already exists and it's called a peltier.
    • t would probably need a special holding case otherwise your backpack would catch on fire while carrying it.

      No, just fold it in half so that the cold sides were facing out.

      • by _0xd0ad (1974778)

        No, fold it in half with the hot sides facing out. That way there's a limited amount of heat trapped inside it for it to move out; when the middle reaches absolute zero it simply can't continue moving heat across (actually, it'd undoubtedly be an asymptotic approach, but that's beside the point).

        What you suggested would cause the inside to get hotter and hotter, making your backpack colder in the process. And even whatever magical material you used to make the hotpad has to have a melting point somewhere...

    • by vux984 (928602)

      oblig...

      In this house we obey the laws of thermodynamics.

  • by KDN (3283)
    Sounds like the Cone of Silence from Get Smart. Lets just hope it works better :-)
  • This isn't really like a one-way mirror. With a one-way mirror light travels through it and reflects from it the same in both directions. It's just that the amount of light reflecting from the bright side is much much greater than the 'signal' which comes through from the dark side.

    This is apparently a true 'one-way' material.

  • Can we wrap children up in this new material? It would make my trips outside of the basement a lot more bearable.

  • Unfortunately for the neighbors, the band is more likely to install the walls the other way around. Making a room that can be monitored from the outside (by a sound engineer/producer) while rejecting outside sounds would be ideal for a recording studio.

    • by smbarbour (893880)

      Unfortunately, that still doesn't answer the question of "Why would you want the sound to pass through a wall prior to recording it?"

      • by Zinho (17895)

        You wouldn't; the pickups would be inside the sound chamber, not outside. That's the whole point of rejecting outside sound from the space, get a clean recording of what happens inside.

        That being said, though, I think the right question for a skeptic would be "wouldn't a completely soundproof room and earphones for the producers/engineers be a better solution than this?", to which the answer is, "yeah, maybe". After all, that's what we're doing now in good studios, and the job's getting done. I'm sure if

  • It's called: the irreversibility of impedance! This is why, for instance, a loudspeaker isn't a great microphone, and vice versa.

  • Put the band in a tightly soundproofed room. Put some microphones outside of the room, and amplify the sound from the outside into loudspeakers in the room.

    See? Microphone --> amp --> speaker. One way signal with off-the-shelf stuff.

  • We can hear the idiots inside but they don't seem to be able to hear us.

    • by timeOday (582209)
      No, the root problem there is all the contradictory input they get from competing interests.

      If you're waiting for everybody to agree with each other (or even be consistent with themselves over time) it ain't gonna happen.

    • by cosm (1072588)

      Best political-geek satire of the year.

  • This makes for (Score:4, Insightful)

    by twentynine (984768) on Friday May 06, 2011 @03:10PM (#36050858)
    a better masturbation chamber...
  • by Charliemopps (1157495) on Friday May 06, 2011 @03:37PM (#36051040)
    A material that allows evergy to only pass one way seems like it would defy some sort of law of physics. Imagine a cube made of this stuff that only lets sound in... Would the energy inside the cube continue to build until it erupted in a sonic boom?
    • by _0xd0ad (1974778)

      You mean kind of like what a laser does with photons?

    • by blair1q (305137)

      Almost all materials have differing levels of transmission and reflection of waves. It has to do with impedance difference at the interface.

      The trick here is there are two interfaces. Air-to-wall on either side. What they've done is to make the impedance differences dfferent on the two sides (low-to-high on one side and balanced on the other side, I would guess), and make it work for a broad spectrum of frequencies.

      The question is how much attentuation you get in the transmissive direction. If they're c

  • Just make a soundproof wall; put some microphones on one side and speakers on the other.

    (you'd have to use some basic amplification, otherwise it would work both ways and the speakers would work like mics and vice versa).
  • by EvilSpudBoy (1159091) on Friday May 06, 2011 @04:04PM (#36051274)
    Make a small cube with each wall made of this material so that sound can enter the cube but it can't get out. Next, let it fill up with sound. Take it to the airport, construction sites, concerts, etc...

    Then you leave it somewhere with a sign on it that says, "Open Me."
  • ...was a time traveler!

    AL: *singing away inside booth*
    TIM: Al! Can you hear me?
    AL: I can hear you...
    TIM: Think about that.

  • Buckaroo Banzai can hear the sound of someone crying within the same room while guitar amps and drums are going full blast?

    Quote: Is anybody out there not having a good time?

  • With material like that loudspeakers could be build that won't reflect the sound inside the box back outside through the cone.
    One layer of one-way material on the inside, then one sound absorbing layer on the outside.

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