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Obviously, muscles are involved in producing sound, but usually not directly. I.e., the muscles that control human vocal cords do not actually vibrate the vocal cords--a different set of muscles forces air past them, and the moving air makes them vibrate. Rattlesnakes use muscles to oscillate their tails, but the sound comes from rattle sections hitting each other, with frequency components much higher than the tail oscillation. Some insects have muscles directly attached to a tympal, but the sound comes from individual ribs deformity, again unrelated to the frequency of muscle contraction.

So, are there any animals that produce sound like a speaker, by directly causing something to oscillate at the intended frequency by contracting and relaxing muscles to move it with no intermediate steps?

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  • $\begingroup$ Would hares stamping on the ground count, or must the sound be directly coupled with the air and continuous? $\endgroup$ Commented Mar 11 at 22:53
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    $\begingroup$ As I understand it, crocodilians may be a candidate, but from what I can find, there's little known directly about how their vocalizations are produced; particularly the low growl (circa 8-10 Hz) might fit. $\endgroup$ Commented Mar 11 at 23:03
  • $\begingroup$ @JiminyCricket. Stomping on the ground feels like same category as snake rattles. The sound comes from percussion, not the frequency of muscle motion. Now, if they kept their foot in contact with the ground and jiggled it to induce seismic waves at the muscle frequency, that would count. But even elephants don't do that; they still use air as an intermediary to generate sound waves that couple to the ground. $\endgroup$ Commented Mar 12 at 4:12

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Bees.

Research has been done into their waggle dance. Bearing in mind that inside the hive there are very low light levels, and that only a certain number of bees can be in direct physical contact with a bee at any given time.

The "waggle" of the abdomen occurs at between 12-15 Hertz and is modulated as part of the communication. The peculiar thing is, the sound is quite directional, and at the head, the pressure changes are at a minimum - indicating to nearby bees the direction at that point in the dance, and the direction and amplitude of maneuvers expressed.

The wing beats are pulsed at 20 ms duration at frequencies ranging between 200-300 Hz. These generate near-field sound which is heard by others, detected by the second segment of their antennae, and the sensilla (hairs found all over their bodies, though I'm not sure if it's known which are frequency-sensitive).

There is also my personal testimony:

My dad was an apiarist. When a bee gets angry and decides you're a threat, it releases pheromones which smell a bit like bananas.

When it gets really angry just before it stings, it buzzes a loud high-pitched whine with it's wings, while hovering near or just attached to it's target (me, often enough to not discount it as a one-off). I hypothesize that this gives a signal to nearby bees - more directional that pheromones which can swirl around objects with the breeze. Or maybe to scare the threat away. I'm darned if I can find reference to this phenomenon on-line.

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