Build a room that resonates with sound.

Discussion in 'Architecture & Engineering' started by kwhilborn, Sep 18, 2012.

  1. kwhilborn Banned Banned

    This post is about architecture and engineering and construction. I want to emphasize that.

    Eastern Culture has for centuries believed in beneficial aspects of meditation and chanting Mantras. The idea of chanting a Mantra such as "OOOM" repeatedly is that it vibrates/resonates your body to a frequencies that are allegedly conducive to good health, etc.

    If this is true... (This is not a debate on eastern philosophies)

    A room that could resonate with sound as well as broadcast the sounds with enough volume inside to replicate the experience might appeal to some of us silly westerners who are too lazy to meditate, or even meditate often.

    If you had to construct a device how would you do it?

    My first thoughts are personal units where a plastic encasement would enclose a person from the head down, while a chorus of Tibetan monks gave the required mantra through high volume speakers inside the case. I am thinking; neck down, so as not to damage hearing.

    Perhaps a understanding of anatomy and studies to show the amount of inner vibration that accompanies such chanting would be necessary.

    Would the device be better suspended by springs?

    Would the device be better made of materials that resonate such as high quality spruce like in violin construction?

    Would the device need to be certain dimensions to allow for various wavelengths to flow, or would the concussive force from the speakers alone be better?

    I know it sounds somewhat kooky, but alternative healing is becoming big business.
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  3. wlminex Banned Banned

    Kwilborn: Not a bad idea! . . . reminds me of one (idea) I had a while back . . . . a vibrational hot tub that would do something similar . . . I'll track your thread with interest . . . . let's see what some others have to say . . . could probably make it 'tunable' for ideal or specific resonances.
    Last edited: Sep 18, 2012
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  5. wlminex Banned Banned

    ps/ I DO know that you can judge the quality of an acoustic guitar by how much the instrument vibrates one's tummy when played.
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  7. Aqueous Id flat Earth skeptic Valued Senior Member

    First, you could look at some examples for echo chambers used in recording studios.

    It turns out that a room can be modeled as a resonator with a frequency response that depends on the dimensions and geometry of the room.

    Human voice, by the old Bell Labs standard, is adequately intelligible between 400-4000 Hz. So call that the passband of your bandpass filter and look for rooms that fit that frequency response, and you'll get plenty of resonance.

    You want walls that are reflective, meaning very flat and stiff. You may have noticed, concrete stairwells tend to echo well.

    You want a room that doesn't require too much air between reflections, since this attenuates the power.

    The more parallel the surfaces, the greater the odds of repeating the bounce. A cube would do the trick. But other shapes will echo more uniformly over the spectrum. Slice a pyramid in half and take the bottom section with a roof over it. It would render a wider band than a cube.

    If it's for chanting, and you want to go crazy with this idea, I would try a folded horn. The idea is to chant into the throat of the horn, but then allow it to fold back on itself so that the mouth of the horn comes back and envelops you. Now place this in one of the reverberating structures and you'll get the natural gain of the horn to enhance the effect.

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    Ignore the HF horn on top. Imagine a hole at the center of the frontmost ridge into which you chant. The sound will wrap around and envelop you. Now place this inside of a natural echo chamber, or build it into the overall design.

    Remember, no carpet or rugs, nothing to absorb the energy. Concrete or plaster seem to work best as long as they're finished flat and tight.
  8. wlminex Banned Banned

    Anyone out there work for Bose? . . . . bet they can help.
  9. kwhilborn Banned Banned

    Thank-you both.

    Bose could probably show you a car that resonates just fine

    @ Aqueous Id,
    Chanting Mantras creates a natural vibration within someone. The idea would be to replicate artificially, so there would be no chanting involved. The participant should be free to read a newspaper or watch television. I suppose inner reflection might be more fitting with the mood however.

    You suggested lowering air travel to keep the strength. This got me thinking of pressurizing. Since the idea is to vibrate the body pressurizing the chamber somewhat might make sense even if impractical. If the person was also breathing pressurized air then maybe it would help carry the sound through the lung areas.

    With the wide variety of baby boomers seeking alternative health soon this could be a fun project to actually build/sell/rent.
  10. Aqueous Id flat Earth skeptic Valued Senior Member

    Pressurizing the air would place more air molecules in the path and increase the attenuation. Besides, you'd be subjecting the users to the bends. Obviously you could do this rather cheaply with a mic, amp, speakers and sound effects box or PC. But I think you'd be pleasantly surprised how well an acoustical echo room works. Incidentally you can almost arrive at this by looking at recording studio design, and doing the reverse of what they do (to cancel echo).
  11. Buddha12 Valued Senior Member

  12. Bowser Life is Fatal. Valued Senior Member

    A box of 1/4" luan plywood that is framed around the edges. I bet that would resonate very well.
  13. Fraggle Rocker Staff Member

    I think you mean 40-400Hz.

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    That's the range of normal speech including the first couple of octaves of overtones that give it character and allow us to distinguish different people's voices.

    400Hz is somewhat higher than the normal speaking range for men. Only a few exceptional sopranos in history could hit 4000Hz: that's approximately B7, nearly four octaves above middle C. Mariah Carey is one of those rare ladies, if you're wondering what a B7 sounds like. Or even a B8, beyond the end of the piano keyboard.

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  14. Trooper Secular Sanity Valued Senior Member

    Room acoustics…interesting. I was just asking about this, and I was a little confused about the bass loss problem, since low frequency travel further. So, I’m assuming that the bass loss problem only occurs because the ear discriminates against low frequencies more, not because low frequencies dissipate more with distance than higher frequencies, is this correct?

    Most rooms absorb less sound energy in the lower frequency ranges resulting in longer reverb times at lower frequencies, which can be partially overcome by designing the room so that its reverberation time for low frequencies is greater than that for high frequencies.

    Hmm…I’m still not completely clear on reverberation. It’s a little confusing. In the outdoors, can lower frequencies sound louder? Is it correct to say that the Doppler Effect is the only distance relation that can change the pitch? Distance alone, does not affect the pitch, right? Is there anything else other than the Doppler Effect, such as the ground effect, or temperature, that could possibly alter the frequency?

    P.S. I love whispering galleries. Legend has it that Adams exploited this effect in Statuary Hall by pretending to be asleep.
  15. Aqueous Id flat Earth skeptic Valued Senior Member

    Good point. I was actually merging two ideas, but the bass horn I had in mind would indeed have an upper cutoff around 400 Hz. The 400-4000 Hz band came to mind and appended itself, since that's about where telephony (folks like Bell Labs) long ago established (from studying speech intelligibility) that the telephone equipment could limit itself without much loss of intelligibility.

    While it's true that vocalized speech wouldn't need this high end, unvoiced phonemes, like fricatives, can only be distinguished in the upper register.

    Incidentally, I have a completely off-the-wall (literally and figuratively

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    ) notion that birds may used the audio spectrum differently than is immediately obvious. One day I got the notion to listen to bird song in slo-mo. I was surpised by the alien sounding glisses, pops and roars that certain songs decompose into. The more I listened, the more I started to detect reverberation, as if they were doing some sonar of a sort.

    As for the room acoustics, though, I think reverberation in the 400-4000 band is a piece of cake.
    Last edited: Sep 22, 2012
  16. Aqueous Id flat Earth skeptic Valued Senior Member

    I think both are true. One problem in the lower frequencies is coupling the driver to the surface area of air that corresponds to the wavelength. The tuba does this by gradually coupling the load along a continously increasing cross section. Folded horn speaker cabinets replicate this, and the subwoofers sacrifice it, paying instead in sheer power to compensate.

    I know an acoustic engineer who designed "traps" - long boxy chambers of all sizes - running out of studio, mostly from the ceiling which was finished in a kind of grille cloth - in order to allow long waves to dissipate rather than to fold back, producing phase distortion, which surprised me at the time. Thinking back on it, I can appreciate his logic.

    I think of it as the summation of the waves coming from a sound source plus many copies of that signal arriving at later times, mixing in amplitude (frequency and phase) and giving us a dimensional perception of audio space - particularly as two ears will detect slight difference in combinations of phases as these vary slightly with position.

    I think it's harder to load the air mass outdoors with the longer waves, which is why folded horns are always seen at big events. But it would also be true that the phase distortion problem goes away when you take the long wavelength out of the cavity of a room and allow the wave to attenuate naturally.

    I can't think of any other.

    I can't think of anything other than distortion which generally only affects a few harmonics. Distance alone would only affect phase, which usually is undetectable to the average ear for the average sound. The Leslie speaker exploited this well, I think, to make for a kind of sound experience that makes live listening so much more enjoyable. Here I'm referring to the speaker reflector that sits on a motorized turntable with a clutch that spins it up and lets it decelerate. By throwing the sound around like this it sweeps all the possible angles for reverb and echo while the main lobe of the radiator also strobes your ear, like tremolo. Plus you get a little Doppler. I think this would be pretty exotic as an enhancement to a "whispering room" converted into some kind of "chant enhancement" room.


    Also note, the aperture that emits the higher frequencies tends to be more narrow in its beamwidth. Thus, lower wavelengths do indeed diffract and need more power to push them in the same angle as the narrow beam higher frequency emitter.

    I think I've heard that. I've been to places like that--one was at the Smithsonian. If the room is finished with a hard surface, in the form of an ellipsoid, then one person standing at one focus can simply whisper, and a person at the other focus will receive the sound intelligibly. It's because all the "rays" of sound from one focus, emitted in any direction will converge at the second focus as a summation, so there is little loss of effective radiated power. It occurs to me that this could be exploited in the "chant room" (albeit not as natural a solution) by having a mic pick up the voice at one focus, process it thought an effects box or PC and send the amplified result to a speaker at the second focus causing the feedback to be naturally presented back to the ears at focus #1.
  17. Trooper Secular Sanity Valued Senior Member

    I befriended a few AVS nuts during the design and construction of a man cave. I once thought AVS geeks, excited by phosphors, only appreciated chin music, but they’re edifying, I’ll give them that. Under a tight schedule, I had to pull wire for a whole-home system with a broken rib. I had hiked after a freezing rain. Despite having the wind knocked out of me, it was breathtaking. I also considered designing sound mirrors at each end of my long hallway. More of an outdoors kiddy thing, though.

    I was having one of those TOT moments, a relief, but more similar to the "Duh! effect" than the "Aha! effect." I couldn’t recall a searchable term, “Sound speed gradient.” I think that anything that changes the density of the medium, such as temperature, pressure, or wind can alter the pitch.

    I was a little curious about how the brain hears distance. I also found selective hearing a bit intriguing.

    Going back to the Aha Effect with a little side question about the sensation. It does feel as though it’s coming from someplace else, doesn’t it? With the problem always lingering in the back of the mind, when those in the know encounter a clue, they can recognize it, and capitalize on it. Without consciously thinking about it, it rises suddenly, and produces a strong emotional response.

    Have you ever noticed how cranks seem to rely on this sensation with their epiphanies, or their so-called insights through the divine? They refuse to accept that knowing what you need to know is extremely important.

    By the way, your perspective is eclectic, which makes for a good conversationalist. Thanks for the information. I found it interesting.

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