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I'm working on a setting with a really old, sentient rock. While its able to think, and has an excellent memory, it has no moving body parts - because it is a rock.

The idea is that it can vibrate to produce sound but I'd like to check what sorts of sounds a vibrating rock (or crystal) can make. I don't know the academic jargon of speech but I know that most sounds that humans make rely on mouth and tongue movement - which a rock or crystal does not have. I assume given the capability of varying its vibrating frequency my sentient rock would be able to produce all the vowel sounds but none of the consonants? I'd just like to confirm/debunk this through the crowd.

  • I'm not concerned with the limitation that different rocks would be restricted to different sound ranges, would just like to know the total range of sounds.
  • I'm not concerned with how the rock would generate the energy to make sound.
  • I'd prefer to avoid hooking up my rock to any contraptions to produce additional sounds, I'm just after the set of sounds a rock could make on its own.

Yours in good faith, Alot

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    $\begingroup$ "I'm working on a setting with a really old, sentient rock. While its able to think" sentience is the ability to perceive. The ability to think is called "sapience". Same root of the word as in "Homo Sapiens" $\endgroup$
    – VLAZ
    Aug 30, 2022 at 9:20
  • $\begingroup$ Whilst you may not be concerned as to how it makes the sound - in order to answer the question with anything but random opinions - we need to know that detail. $\endgroup$ Aug 30, 2022 at 11:21
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    $\begingroup$ Your computing device on which you have typed this question has one or more loudspeakers. Loudspeakers do not have tongues or mouths, and yet their vibrating membranes can produce all the sounds humans can make, and infinitely many others. $\endgroup$
    – AlexP
    Aug 30, 2022 at 11:54
  • $\begingroup$ You might be interested in this video - somewhere in the middle is an appearance by "the Rock", a resident of the Pointless Forest. A sentient, sapient rock with the wisdom of the ages. And The Rock makes a point without having a point. $\endgroup$ Aug 30, 2022 at 12:05
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    $\begingroup$ I upvoted Zeiss Ikon's answer (great answer!) but need to VTC this question. It's missing important details. Right now we're answering this question from the perspective of "what sound can be made by vibration?" Answer: all sounds. Were that true, human vocal range would be breathtaking. Unfortunately, due to how we make sound, we're limited in what we can do. You have not explained how your sapient rock causes vibrations. You have not even explained (*continued*) $\endgroup$
    – JBH
    Aug 30, 2022 at 15:47

5 Answers 5

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Many years ago, before Windows became a major force in the world, there was a sound driver for some DOS games called "RealSound". It allowed the basic PC speaker (which was driven by a 1-bit digital signal -- that is, either on or off, though capable of switching at pretty high frequency) to produced fairly natural-sounding music, sound effects, and even voice via "FM Synthesis" -- this was managed by feeding rapid on-off pulses to the speaker's driver at varying frequencies that took advantage of the inertia of the speaker's voice coil to smooth the output into natural-seeming sound. The quality was lower than a real sound card (like a Sound Blaster or Turtle Beach), and it had more digital artifacts (harmonics, mainly), but it was very intelligible and made games much more enjoyable on computers that didn't have a sound card (which was a not-cheap add-on device in the late 1980s). Current Linux versions provide snd-pcsp driver which does similar thing even on modern PCs if they're equipped with a traditional PC speaker.

All of that to say, your sapient mineral might only have a single vibration mode, but that mode can be operated at rapidly varying frequencies to produce the same kind of FM synthesis the RealSound driver did in 1989. That not only would allow a range of frequencies from infrasonic to ultrasonic, but allow synthesizing a full range of waveforms -- covering everything that any animal could produce with a fleshy vocal apparatus.

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    $\begingroup$ While I like a checkmark as well as the next guy, we usually recommend waiting a bit (24 hours?) before accepting an answer. An accepted answer tends to discourage additional answers, and there might be a better one from someone who hasn't yet had a chance to see this question. $\endgroup$
    – Zeiss Ikon
    Aug 30, 2022 at 14:54
  • $\begingroup$ I believe this answer is flawed. Even if a mineral object were to be elastic enough to oscillate slow enough to be heard (~40Hz-20kHz), a single mode of vibration (by definition) oscillates in a sinusoidal shape. Such an oscillation cannot create pulse width modulation a la RealSound speaker drivers. That requires discrete (or at least nearly infinitely fast) shifts between at least 2 and ideally 3 steady states. Does this rock posses quantum mechanical properties? This scenario also requires a decoder (e.g. a computer speaker's solenoid) to smooth out the pulses into a speech-like waveform. $\endgroup$
    – dmedine
    Sep 6, 2022 at 3:16
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Theres an impedance matching problem, your sentient rock using @ Ziess Icon's method and figures out how to modulate it fundamental frequency and can produce the signals. But the speed of sound is fast in the rock, and slower and the air and because it's a hard rock the amplitude of the vibration is very small the vibrations don't couple very well to the air. So the sound doesn't very far. It does couples better to the ground, perhaps through other rocks at lower frequencies. Or perhaps to a pool of water.

But, if someone puts their cheek bone to the rock they would be able to hear the higher frequencies better through bone conduction.

If there is a hole in the rock to have a resonating chamber and thin membrane over the hole, the rock discovers it can shout.

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  • $\begingroup$ Thanks, that was very helpful. $\endgroup$
    – Alot
    Aug 31, 2022 at 7:41
  • $\begingroup$ While the vibrations might not translate to much sound using rock-air interaction, the sound would be audible when the rock is resting on a surface. Think about how loud a vibrating cell phone is in your hand versus sitting on a hard wooden table. The rock-surface interaction would produce ample sound. $\endgroup$ Aug 31, 2022 at 10:41
  • $\begingroup$ @GregBurghardt only if the surface was a table or equally resonant surface. $\endgroup$
    – dmedine
    Sep 1, 2022 at 2:45
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Pan flutes

Depending on how the rock is structured it may have multiple holes, with each of these holes having a cavity behind it, of varying lengths. When the creature vibrates its not to make the sound directly but instead to push air through the holes in its body. By having many cavities with different lengths it can produce many different frequencies. Once you can make a large number of different frequencies, they can be combined in different ways to produce actual sounds.

Also means when it gets windy your rock is going to sound like its screaming and/or a pan flute concert.

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I thought of another way that a rock could make sound without it actually moving. There is a process for mixing frequencies that produce a set of new frequencies, one at the sum of the frequencies and one at the difference. These are known as heterodynes (https://en.wikipedia.org/wiki/Heterodyne).

Now, lets suppose that this rock is marbled with conductive material like veins of ore. Lets also say that it is full of chunks of quartz and similar crystals that oscillate at very high frequencies when electrical current is applied. Provided that the rock is somehow connected to an electrical power supply, perhaps whatever lives inside of it to make it think and remember things can also manipulate the flow of electrical current throughout its structure (animal neurons do that, so why not rock neurons?), mixing high frequency oscillations in its various crystalline sectors to produce heterodynes in the audible range. With this facility it could synthesize vowel sounds via additive synthesis. Give it the ability to ramp up and down the amplitude of the heterodynes rather quickly and it can reasonably approximate many consonants as well. At this point it could potentially sound like the vocal track on a Kraftwerk album. Give it a few holes to serve as resonant chambers and people walking by might be able to hear it as well.

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  • $\begingroup$ Thanks, that's extremely helpful $\endgroup$
    – Alot
    Sep 2, 2022 at 5:59
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0-32768 Hz

wait what?? that literally cover really wide range of frequency's spectrum . According to Wikipedia, we can calculate frequency that certain mineral can make by using it Density, Young's Modulus and it's size in term of Length, Radius by assumed that it sharp like cylinder, or close enough (for the sake of simplicity)

well, I made a formula to calculate frequency using tuning fork formula. Apparently, with certain length and radius you can achieved a very high frequency with commonly mineral such as quartz

The thing that will really determined your sapience mineral's frequency range is it size.

-say 50 cm tall, 10 cm radius quartz(1000 GPa with 2600ish kg/m^3 density) can produce 2250 hertz.

-while hand size (10 cm length, 3 cm radius) can produce 16945 hertz.

(32768 one is human-crafted)

so if you limited the smallest mineral being or something to hand-size, the frequency range that they will use for communication probably be 0-10000ish hertz. or you can go testing out yourself in formula. (other info such as Density range, Young's Modulus range also provided)

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    $\begingroup$ Free oscillations and driven oscillations are different things. $\endgroup$
    – AlexP
    Aug 30, 2022 at 12:48
  • $\begingroup$ Frequency doesn't have a spectrum. It is simply a number corresponding to how fast something oscillates. It has the same range of values as does the set of all complex numbers. $\endgroup$
    – dmedine
    Aug 31, 2022 at 10:45

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