Is there such a thing as a speaker that turns music into vibration?
June 12, 2020 3:30 PM   Subscribe

I'd like to either purchase or make speakers that are very low frequency so that the sound they emit can't really be heard, but only felt.

If this is possible, I'm not sure if the music itself also has to have very low tones or if the speaker can just turn whatever is playing into low tones so that it can be felt.
posted by fantasticness to Technology (20 answers total) 4 users marked this as a favorite
 
To me that sounds like what a subwoofer does. The sound is coming from your other speakers and the subwoofer just provides the rumble. I'm not sure what would happen if you just hooked an audio source directly to one though.
posted by any portmanteau in a storm at 3:34 PM on June 12, 2020


This is what all speakers do. Bit the speaker can't turn what it's playing into "low tones". It only attempts to reproduce what it's given.

So to get what you want, you'll to use music with VERY low frequencies, and the speaker will need to be able to reproduce those frequencies. Also, low frequencies need more power to reproduce than higher frequencies, m so you'll need a powerful amplifier.
posted by jonathanhughes at 3:43 PM on June 12, 2020 [2 favorites]


Yes, you can definitely do this, the problem is scale and disruption to other people. If you want to use a traditional speaker design that can transmit this across a room, the vibrations are going to be very dramatic and will literally shake the room. I've felt this at electronic music concerts with very large amplifiers, but it's not something you want to do at home.

A better idea is probably a personal device that attaches to your body, because that can be a lot more precise with vibration without disrupting others. They make a variety of these devices, based on this KQED article it seems like the Subpac is a popular option, but they're currently sold out it looks like.
posted by JZig at 4:12 PM on June 12, 2020 [4 favorites]


Perhaps you are looking for a kicker? Not the brand name of speaker; a type of transducer sometimes used in home theaters that attaches to the bottom of the seat so that you feel the low rumbling through your body. Some find them preferable to large subwoofers run at high enough power to get a similar effect from a speaker, which tend to produce sound that carries for very long distances.

In any event, the media being played has to contain low tones within the range of the sound reproduction device you are using to produce any noticeable effect.
posted by wierdo at 4:12 PM on June 12, 2020 [1 favorite]


Perhaps a bass platform that a professional musician might use to “feel” the music on stage?
posted by gnutron at 4:40 PM on June 12, 2020 [1 favorite]


Could try something like this?
posted by aramaic at 5:16 PM on June 12, 2020


You might want - or at least want to try - a ButtKicker. These physically attach to a chair and rumble it in the sub-audible range.

But as others have said, you'll only get the lowest frequencies. You're not going to be able to hear lyrics or anything other than the lowest part of the audio.

They do not appear to be common on facebook, craigslist, or eBay.
posted by Hatashran at 5:30 PM on June 12, 2020 [1 favorite]


Here’s a home theater version that claims response down to 1 Hz.
posted by doctord at 7:06 PM on June 12, 2020


Google "Bone conduction speaker" and "Bone conduction headphones". There used to be a product called the "Bone Fone".
posted by 445supermag at 8:10 PM on June 12, 2020 [3 favorites]


Along the lines of a bone conduction speaker, your question made me think of Laurie Anderson's Handphone Table.
posted by Rube R. Nekker at 8:47 PM on June 12, 2020


Shorthand for the human hearing range is (used to be?) 20-20khz.

Anything below 20hz is literally not hearable. Any music you try to imagine does not exist. What would you 'play' that low?

I guess you could digitally slow something down so the mid-range is well below 20hz. It's gonna need a super clean high gain amp.
posted by j_curiouser at 9:23 PM on June 12, 2020


Further...professional mics don't have a response below about 30hz.

I dunno what movies and games are specifically doing to record 'vibrations', but it's digital hijinx, not actually recording the *sound* of an explosion (or anything else).
posted by j_curiouser at 9:31 PM on June 12, 2020


445supermag — OMG I own a Bone Fone. I brought it back to life from a Goodwill bin.

However I can confirm it is sadly just a pair of speakers sewn awkwardly into a scarf. The “magic of bone conduction” described in the manual is bunk.
posted by sixswitch at 12:37 AM on June 13, 2020 [2 favorites]


Sound can indeed be recorded below 30Hz, but not generally by microphones that can also record at 20kHz. These frequencies below the range of human hearing are sometimes called infrasound.

To answer your question, we should first clarify exactly what sound is. It is a pressure wave that travels through the air, and the variations in the pressure push on your eardrum, causing it to vibrate. These vibrations are then detected and transduced by the bio-mechanical-electrical systems in your ear into nerve impulses which go to your brain and are interpreted as sound. The vibrations are detected and encoded in a clever fashion, but broadly speaking the motion of your eardrum is exactly measuring the pressure in the air at a given time, with the changes (vibrations) happening as rapidly as 20kHz, or 20,000 times per second.

Microphones work the same way as your ear. They have a tiny pressure sensor, typically some flexible membrane, which vibrates exactly along with the pressure variations. The motion of the membrane is then converted into electrical signals.

Speakers are the opposite of microphones: they convert electrical signals into vibrations, with a membrane that pushes on the air to create a pressure change. Speakers are divided into woofers, tweeters, etc, because it's next to impossible to build a device that can vibrate and create a large sound at, say 30Hz, but can also vibrate reliably at 20kHz.

So the first answer to your question is any speaker at all. If you touch the surface of the speaker membrane, you will feel the vibrations of the sound coming out of the speaker. You will also probably muffle the effectiveness of the speaker, meaning it can be felt but not heard. This is how the bone conduction speakers work. They are just speakers, but they are meant to vibrate against your skull, which then causes your eardrum to vibrate, bypassing the air.

If you want to feel vibrations at a distance, transmitted through the air like sound, then you need a powerful woofer. As others have said above, this sound will carry and leak out of any building you try to contain it in.

With a woofer, you can directly play (and feel) the low frequency tones in the music. You could also definitely downconvert other frequency bands to lower frequencies and play/feel them through the woofer as well. This is not to my knowledge a standard technique in any audio/music system but it is standard in signal processing and would be easy to do if you route the audio signal through a digital signal processor. With this kind of processing, and the right woofer, you could definitely get sounds that are felt but not heard, from any music as a starting point.
posted by indecision at 1:08 AM on June 13, 2020 [6 favorites]


It sounds like you’re looking for bass shakers. Here’s a site that explains them and has a number of reviews.
posted by Slinga at 3:09 AM on June 13, 2020


professional mics don't have a response below about 30hz.
This is inaccurate. Microphone frequency responses often drop off sharply around this range, but a professional condenser microphone, while generally tailored to that 20-20kHz window mentioned above, can often pick up both frequencies both above and below that range depending on its design.

Likewise, subwoofers generally produce sound in the 20-200Hz range, but this isn't a hard limit - there are subs that go well below 20Hz, although there's a sharp drop-off as you get closer to 5Hz (IIRC this has something to do with protection against DC power). You can send low frequencies to any random driver if you can generate the signal, but it may very well break the speaker before it produces anything like audible sound.

Now to OP's question, most commercially-produced music will not have much information below 20Hz, BUT 20Hz through a good system is more than enough to shake your glasses out of a cabinet, and is low enough as to be basically inaudible to many people. In middle age, my own hearing only goes up to about 17Kz reliably and drops off around 28Hz - below that I feel it rather than hear it. If all you want is the low frequencies, any ordinary subwoofer will usually have a crossover pot and allow you to play around with the builtin low-pass filter until you get only the rumble.
posted by aspersioncast at 10:32 AM on June 13, 2020 [3 favorites]




Thanks for clarifying, aspersioncast. I feel smarter now!
posted by j_curiouser at 4:20 PM on June 13, 2020 [1 favorite]




Bone conduction is what you are looking for.
posted by oceanjesse at 7:22 PM on June 13, 2020 [1 favorite]


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