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I was thinking of a creature that uses ultrasound to echolocate and infrasound to communicate with its species.

The current idea is a dog-like creature that hunts in packs, due to a large avian predator they developed infrasound to communicate at a pitch that cannot be heard by the predator and their prey.

The Dog-like creatures are also blind so their main sensory method is ultrasound for echolocation.

Can a creature make both ultra and infrasounds? would they need a specific shape of body to achieve this?

Edit: I don't think any animals use both very low or high frequencies, creatures like an elephant or giraffe have long resonance chambers to create the low sound, would a creature need two resonance chambers one shorter one longer, would a dog-like body be able to make both sounds?

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  • $\begingroup$ Why can't they communicate in ultrasounds? $\endgroup$ – Thymine Feb 26 at 14:56
  • $\begingroup$ @Thymine I wanted them to be able to communicate over large distances and have the communication not lost in the echolocation noises. $\endgroup$ – RandySavage Feb 26 at 15:01
  • $\begingroup$ Echolocation would be one steady pulse signal, easy to distinguish from communication noises, which is how bats or dolphins can communicate and echolocate. If the distance you want them to be able to communicate over is long enough I can see why you want infrasound in addition to ultrasound $\endgroup$ – Thymine Feb 26 at 15:10
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Great Curasows have the largest vocal range that I know of, their range runs from 100 hz up to 7 Khz (Source), and I see no reason why that range couldn't be increased or shifted to span both ultrasound and infrasound. Also, there's no reason to think that you need ultrasound levels of sound in order to echolocate-- there are documented cases of blind humans using echolocation using their limited vocal range.

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  • $\begingroup$ Great example thanks, do you think I need an enlogated neck, similar to the bird to achieve the sound range? $\endgroup$ – RandySavage Feb 26 at 16:38
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    $\begingroup$ @RandySavage I don't think so, though I suppose longer vocal chords would have the capacity to produce a deeper bass note. Black Curasows also make a low "booming call" and they have comparatively short necks. I've seen Great Curasows make this call in the wild and the power seems to come from their bodies which sort of inflate like a set of bagpipes see here: youtube.com/watch?v=44NNQ5I7VjA $\endgroup$ – Dugan Feb 26 at 16:55
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Oh nice, something I know a bit about. Let me ramble on about this great length.

So, the thing to remember about sound is that it only really interacts with things that are about the same size as its wavelength. As you probably know, wavelength is inversely proportional to frequency, so high frequency sounds interact with little things, and low frequency sounds interact with big things.

For example, if you have a small hole in a wall, low frequency sound will ignore the hole, and reflect off the wall, and high frequency sound will go right through. Alternatively, if you have a small bit of wall standing by itself, the high frequency sound will reflect off it, but the low frequency sound will just spill round the edges, no problem, and carry on past.

What does this have to do with anything?

Well, if you're using sound for echolocation, your resolution is defined by the frequency of the sound you're using. If you tried to use low frequency sound for echolocation, the sound energy wouldn't reflect off anything smaller than the ground or a big wall or something.

Hence, creatures that use echolocation use ultrasonic frequencies.

But, high frequency noise is terrible for communication, because you basically need line-of-sight (also it gets absorbed by the air) so your range is low as hell.

So, you'd need two distinct systems, really.

The same rules apply (ish) for generating sound. Its very inefficient to generate low frequency sounds with a small thing (as you're fighting the mass of the air) or high frequency sounds with a large thing (as your fighting the mass of the thing).

So your dog things will need two hearing systems, and two noise generating systems, one for each purpose.

Low frequencies carry quite well through solid objects, so maybe they transmit their communications into the ground by impacting the ground, and hear with their feet. Think about a cowboy putting his ear to the ground to hear a stampede or touching the rails to check for trains. Or go the more traditional route and have a resonating chamber like elephants or whales, but this would need to be quite big and would use a lot of energy to use. It would probably want an opening, like a big nostril or something.

The high frequency organ could be small, but would need to be on or near the surface of the body, so that the high frequencies can escape. Think about a bat's face, or a cricket's legs. Maybe, just like crickets, they generate sound with friction on the surface of their bodies. The ears for high frequency should be big, as they need to collect as much energy as possible, and giving them a complex shape will help with detecting directionality (which I could talk about for as long again).

I should stop now, but I could carry on for as much again very happily.

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As long as the prey isn't human, you don't need to worry about your creatures being able to produce infrasound and ultrasound, you only need to worry that they're able to produce a range of sounds broader than those that can be heard by their predator and prey.

For example owls have a hearing range of 0.2 kHz to 12 kHz. To an owl, 0.02 kHz is "infrasonic" even though it is not to us, and 13 kHz is "ultrasonic" even though it is not to us.

So, as long as it's broader than the hearing range of prey and predator, you can safely have a creature that is capable of producing sounds that are impossible to hear from both sides of the spectrum.

Now you need to know if there are limitations on which frequencies can be effectively used for ultrasonic echolocation, and which frequencies can be effectively used for infrasonic long-distance communication.

Echolocation frequencies are tailored to the environment. In good atmospheric conditions and to capture relatively large insects, some bats have echolocation frequencies as low as 11-12 kHz. That's a reasonably low range to aim for, particularly when you consider that it's sufficient to pluck insects out of the environment, so it's still a high resolution scan of the surroundings.

Infrasonic communication, in order to be effective over long distances, needs to be very loud. This is why you need a relatively large animal such as an elephant, giraffe, whale in order to really take advantage of this type of communication by making it loud enough. You might want to aim for an infrasonic range similar to that of elephants or giraffes since they're terrestrial animals. I think that whales can afford to go a bit higher with their songs (30~40 hZ) due to the sounds being propagated by the medium of water rather than air.

You might find this website useful if you want to go very deep into the science of animal communication.

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  • $\begingroup$ Thanks, there are a few less massive creatures like tigers that can make infrasonic sound which makes me think I don't need massive for low frequency, for ease of story telling the predator and prey will not adapt to this creatures level, do you feel a standard dog is too small for both vocal needs? $\endgroup$ – RandySavage Feb 26 at 16:01
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    $\begingroup$ Being massive is less about being able to produce the frequency and more about being able to produce it loud enough for it to carry over a long distance without being too dampened $\endgroup$ – Thymine Feb 26 at 16:09
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Yes, why not?

Infrasound and ultrasound are defined as sounds that are too high or too low for a human to hear. The same goes for infrared and ultraviolet light: they are beyond a human's capacity. But it is easy to think of a creature that has simply broader range in their hearing or vision. And if it's broader, there's no reason why it should be limited to one side of the spectrum. Those limits that we use are fairly random, and have no meaning without a human as a reference frame.

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  • $\begingroup$ its just that ( from a quick google search) we don't have any creatures that use both, it made me think the creature would either need two resonance chambers or some other anatomy to deal with the pitch? $\endgroup$ – RandySavage Feb 26 at 15:03
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Sure. It's called a cow.

enter image description here

Wikipedia - Hearing Range

This puts the ranges at:
31Hz-19kHz for us pitiful humans.
23Hz-35kHz for our new overlords, the cows.

Moo.

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    $\begingroup$ "23Hz-35kHz for our new overlords, the cows." Long live the Ferret Emperor: 16Hz-44kHz. $\endgroup$ – Adrian Colomitchi Feb 26 at 15:37
  • $\begingroup$ Haha that reminds me of a Brickleberry episode, only India will be sparred because they worshipped cows, lol as Adrian said ferret is king too, but this is hearing range, it doesn't mean they can make those sounds them selves? $\endgroup$ – RandySavage Feb 26 at 15:39
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    $\begingroup$ This is hearing range though-- not vocalization range. OP's question is about animal's ability to produce the sound. $\endgroup$ – Dugan Feb 26 at 15:58

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