How effective/plausible is vibration sense in the air?

Question

I am developing a fictional species of raptor or raptor-like bird, with incredible senses, for a fantasy setting. One element of their combined sensory picture that I thought of was the use of sensory organs that detect vibration to an incredible degree, similar to seals underwater.

This means the ability to detect vibrations (or something similar if I'm using the wrong word) at great enough ranges and/or long enough after the signal producer is gone to be practical. Obviously the difference here is that these fictional raptors would be using air as the medium not seawater.

For the sake of the question assume the atmospheric composition is like that of earth, unless you need to change it slightly to make it plausible then by all means include that in your answer. Also, please ignore how the animals would interpret these senses, I am specifically interested in the mechanical plausibility. If necessary assume the raptors have a built-in filter for the clutter of air rushing past the sensory organs. I am not interested in answers involving sonar.

So, is this type of sense possible in any form in the air? If so, what is the method; whiskers, organic pitot tubes, something else? If it is only partially possible, such as at short ranges or under specific conditions or in specific circumstances, what would those be?

Thanks in advance!

EDIT: After having been made aware that hearing is based off of vibration, I want to clarify. I have seen tests where seals follow the path of submersible drones, after the drone had finished its course, whilst blindfolded. This was attributed to the seal's whiskers as a sort of touch sense, seperate from hearing. So would a similar thing work in air where for instance the fictional raptor might track aged signs of movement or does the atmospheric medium prevent this?

EDIT 2: One rough theory I have just brainstormed is as such. Given the correct biology, could these birds be able to feel turbulence in the air, such as after other birds pass by at a distance, and follow a path of turbulent air like a boats wake?

Answer 1

YES

The sense of hearing is exactly what you're describing! Although, a different sort of hearing, as you're not specifically interested in the primary sense of hearing through the ears.

Vibrations in the air impact the tympanic membrane (eardrum) & are transmitted through the ossicles, the three tiny bones that amplify the vibrations. Their motion is then transferred via the oval window to the inner ear fluid which causes the the hairs within the inner ear to vibrate in sympathy. When activated by sound waves, the cells pertaining to the hairs that are reacting to the specific frequencies of sound produce neurotransmitters that activate the nerve cells to transmit signals to the brain. The brain then interprets the sounds.

All you need is a similar set of receptors that can detect and relay signals. You mention seals and their whiskers. Your creatures could have lines of specialty feathers or hairs, perhaps along the body, or perhaps in the mouth or nasal cavity or along the lips that sense & transmit the signals you're after. Physiologically this sense is entirely plausible. Though I think you're going to want to explore further how this came to be: what evolutionary factors (darwinian or lamarckian, doesn't matter) are at the foundation of this sense.

I would consider what seals are doing, as well as what your raptors are doing, another kind of hearing, an accessory auditory pathway, as they both are sensing pressure waves in a medium. Just as the Flehmen's response is another kind of sense of smell.

One thing to consider is the limitation of such a sense. Sounds that we can hear are generally pretty limited. Sound waves, unlike light, are propagated in a medium, be it some kind of liquid, solid or gas. Unlike light waves, sound waves don't travel very far without a continuous source of propagation. They dissipate and eventually disappear. In other words, the power behind the wave eventually quits and the medium stops vibrating.

I know you suggested a filter that would mask the sound of the air, but I'd actually suggest that your raptors ought to be listening to the air itself. They might detect current changes ahead (and around them) -- thermals, turbulence, downdrafts, updrafts, etc. They might detect weather changes (air pressure changes, as well as the sounds of rain, thunder, etc).

Answer 2

Your questions reminds me of a fish's lateral line, which according to Oxford Languages is "a visible line along the side of a fish consisting of a series of sense organs which detect pressure and vibration." Lateral lines incorporate pits or groves with jelly-like cupolas inside. Extending from the cupolas are cilia, little hairs, and since water and air are both fluid (in a sense) a lateral line should theoretically work in air.

In fact, since the lateral line detects water movement by the displacement caused by motion on modified epithelial (hair) cells, the lateral line should work just fine. Furthermore, plenty of animals communicate by vibrations: elephants, jumping spiders, naked mole rats, termites, treehoppers, and even kangaroo rats.

Put sensitive cilia on the creature's skin (this would make it look a little fuzzy) and it should be able to sense the air moving around it. However, this would not be very effective; water is dense, so it transmits vibrations much better than air. Any kind of motion in water has a larger impact (since more energy is involved) and will be detected much faster by a lateral line.

If this doesn't make sense, consider this: any time a marine creature moves, it creates ripples in the sea, it changes the water pressure slightly. In air, however, the ripple effect is smaller and dissipates faster ( I think; I'm no expert on the subject). Some people can feel the air shift just before a thrown object hits them, everyone can sense the air shift when someone dashes past.

As a result, your vibration-sensing creatures will only be able to sense immediately around them. Quick reflexes are strongly recommended for your raptors.

As for feasibility, look to evolution. Supposedly all terrestrial life evolved from marine ancestors, so all you need to do is explain why these creatures not only kept their lateral line and swim bladder, but adapted them to live in air.

The most likely explanation would be that they lack eyes; evolution tends to go against re-evolving traits unless there's an actual need, and if these creatures survive without eyes, they obviously don't need them. Such creatures would likely live deep underwater, or in cave systems, and upon reaching land continued to see through vibration.

As for sensing and following turbulence, fish already do that with their lateral lines, so that's perfectly feasible for these fishbirds, as long as they have good hearing as well as vibration-sense, since vibration-sense in air has a really bad range.

Answer 3

This means the ability to detect vibrations (or something similar if I'm using the wrong word) at great enough ranges and/or long enough after the signal producer is gone to be practical.

"After the signal produce is gone" means you would hear them when they are not there anymore. This requires the predator to be some really long distance, because at close range there is practically no lag between sound and image. Sound in air travels at speeds close to 330m/s (about 1,080 feet/second). This also implies that either the prey is really loud or the predator is extremely sensitive.

EDIT 2: One rough theory I have just brainstormed is as such. Given the correct biology, could these birds be able to feel turbulence in the air, such as after other birds pass by at a distance, and follow a path of turbulent air like a boats wake?

Ever been in a place? You can detect turbulence with your innate sense of gravity as your body feels forces randomly alternating in all directions, no need for a vibration detecting sense.

---

You don't necessarily pick up vibrations with just your ears. A good enough sound system will have you feeling the bass with your feet and maybe even your teeth. It would be feasible for a predator that is super specialized to have regular hearing for most things, and a special organ that resonates with some sound the prey makes just for detecting food.

The opposite has already happened in our own world. Some moths have sensory cells in their ears tuned specifically to the echolocation frequencies of bats that eat them. Those receptors are either deaf or "hard of hearing" to any other frequencies. When the moths hear a bat with these ultra-specialized receptors, they take evasive maneuvers.