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I'm not sure if I'm asking this in the right place here, so please forgive me if not. It's a bit of a strange one.

I have a set of water speakers, which I absolutely love, and I'd like to be able to see the water 'dancing' at night with no music. I know that it is possible to physically disconnect the speakers inside, but I'd like to be able to use them as speakers as well sometimes.

I was wondering if it would be possible to use a program like audacity to produce a sound output that cannot be detected by the human ear but still produces a voltage, or something like that. Any suggestions would be appreciated.

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You just need to disconnect the speakers from the water part of the device. It is pretty simple and self explanatory. I was also able to find a Video on YouTube for it. Check it out here.

  • If they want to also hear some sound , a 4 way slide switch and a resister array (simpler than it sounds) could be mounted on the case. Adding some resistance would lower the total power getting to the speakers. – Psycogeek Mar 29 '14 at 22:25
  • Thanks for this, I knew it could be done by physically changing the circuitry but I didn't really want to have to take them apart and I also wanted to be able to hear the sound when I wanted to, but from @Psycogeek's answer it looks like it's the only way so I'll just have to implement a switch – Andy Mar 30 '14 at 11:22
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There are frequencies of sound that fall outside of the range of human hearing, high frequencies are still sound pressure, and do the tiniest of waves, and slow low frequencies that are so slow that it is more like a wind than a thump.
If I was trying to make water move with sound pressure, but to not hear the same sound, I would try and make some kind of very slow bass alogrythm that averaged out the same sound , then moved the water "to the sound" still.

I would be talking about a theory, if I had not already seen it in action, and played with it some. Remember those "activators" for computers and consoles that a person could strap on thier chest , or mount in a chair. The activator would convert electrical energy from the sound to more physical movements. It did this with a huge weighted magnet assembly , passing through a electromagnetic coil.
In these devices they had a switch that would half or quarter the sound waves, taking the same sound and making movements that are 1/2 or 1/4 the frequency. They basically translated all the midrange frequencies to lower, so the physical action of the activator was greater for the mid-low frequencies too.

One of the issues with the physical activators, no mater how much of the sound was being converted to physical movement and not sound output, sound output occurs. everything that is physically moved can create a sound pressure wave. (is why the "voice coil" method of armature arm in hard drives still makes some sound)

At any of the lower freqencies to move the speaker (or thse activator electromagnets) these large distances takes much electrical energy, speaker or activator. By lowering the frequency the ammount of physical movement is longer the power greater. (low frequencies want to move the magnetic stuff longer distances to create the low sounds, more work = more power)

So one way to make water dance to music without hearing as much sound output from the electromagetic activator would be to lower the frequency of the sound it was getting. Many ways to do that, like to change the playback/sample rate without resampling. Extreeme pitch adjustments, octive change and "time" changes all ways to lower the frequency.

Problem still is you would want to lower the freqency only to the activator and not the speaker too, or your going to need an unadjusted speaker output to mask the noises. So any alogrythm would want to be a curcuit in the device, and might also need more power going to the water activator.

That still leaves the best solution what tech1337 provided, to stop or reduce the output to the speakers designed for audible output, and still maintain power to the water activators.

  • Thank you for your detailed answer. My main issue was that I wasn't actually sure on the technical details even though I knew about the physics of the sound. I knew I could produce sound of a frequency outside the human hearing range, but I didn't think about the limitations of the circuitry in the speakers... there was me thinking I was being clever. – Andy Mar 30 '14 at 11:26
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Try jiggling the USB wire (unplugging it and plugging it back in again) until the speakers light up but the sound doesn't play. Then turn up the volume until the water dances. Make sure to turn the volume down again when you put the audio back

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