1. Why Does Sound in the Air Mostly Bounce Off the Water?
Imagine trying to hear a friend while you are underwater in a pool. Their voice would sound faint and muffled. Water and air are very different materials, and a sound wave that meets such a sharp change is mostly reflected. A physics study of the boundary found that sound transmission through the water-air interface is normally weak because of the strong difference in mass density [1].
There is a twist, and it points the other way. The same paper predicts that a low-pitched sound from a source very shallow under the water can escape into the air surprisingly well [1]. That is about sound going out of the water, though, not about the plop of a lure coming in. For a fish, the useful question is not what happens to the sound from the air. It is what the lure's landing does inside the water.
2. What Sounds Does Something Falling into Water Make Underwater?
Scientists have studied this most closely with raindrops. A seminar at KAUST, a research university in Saudi Arabia, described how a drop hitting a pool can pinch off a small bubble from the dip in the water's surface. The researchers matched high-speed video of the bubble with a hydrophone, an underwater microphone, and confirmed that the sound begins at the instant the bubble pinches off [2]. Rain's underwater noise is related to this process [2].
Not every splash makes a bubble. In a high-speed video study, drops larger than about 3.8 mm across, dropped from 3.61 meters onto still water, consistently trapped a donut-shaped bubble of air [3]. A fishing lure is much bigger and heavier than a raindrop and is thrown rather than dropped, so these experiments cannot tell us what a lure sounds like underwater. In the sources we read, nobody measured a lure's landing with a hydrophone. What they do support is a general idea: when something hits water, it can create sound and water movement under the surface, not only in the air above it.
3. How Do Fish Sense Sound and Vibration?
A fish has no outer ears, but it has inner ears inside its head. Ocean Conservation Research, a nonprofit that studies underwater sound, points out something easy to miss: sound has two parts, pressure changes and the back-and-forth motion of water particles, and many fish may rely more on the motion than on pressure, so how close the sound is can matter more than how loud it is [4]. A Japanese doctoral study on carp found that tiny ear stones respond to that particle motion, while a gas-filled swim bladder can take in pressure changes [5].
Fish also have a lateral line, a line of sensors running along each side of the body that detects water movement. In that carp study, the lateral line responded best to vibrations around 40 to 50 hertz, while the inner ear was most sensitive between 200 and 600 hertz [5]. A hertz is one vibration per second, so lower numbers mean deeper sounds. The study also found that carp can tell pitches apart only up to about 700 hertz [5]. This is one species in a lab, so it should not be treated as a rule for all fish.
4. Do Different Fish Hear Different Pitches?
They do. Rainbow trout, a popular catch, were tested at a Tokyo fisheries research center by training them to link a sound with a mild signal and watching their heartbeat. The fish responded to tones from 50 to 1,000 hertz and were most sensitive at 300 hertz. They were worse than cod and red sea bream at telling which direction a sound came from [6].
So a trout and a carp already differ, and the numbers in a lab test do not tell us how a particular lure sounds in a particular lake. We did not find a measurement that places a lure's landing sound or the click of a rattle inside the hearing range of a given fish.
5. Do Noisy Lures Really Catch More Fish?
This is the part that is still open. Many lures hold small beads that rattle, and anglers often swear by them. Among the scientific sources we could read, none gave a clear test showing that rattles raise catch rates, and none showed that they scare fish off either. We could not claim either one.
One thing that does complicate the picture is learning. A 2020 conference abstract from the University of Illinois asks how an individual largemouth bass's learning experience affects its chance of being caught [7]. We could read only the opening of the abstract, which says that for fish targeted by anglers, survival depends on avoiding capture, so the details of the results are not something we can report. If fish learn from being caught, a lure that works on an untested fish might work less well on one that has met lures before, which makes any simple answer about sound harder to find.
6. How Can You Look for Splash Bubbles at Home?
Fill a clear glass with water and put it on a table where spills do not matter. Drop a marble from just above the surface, then from a bit higher. Look through the side of the glass for a cloud of tiny bubbles or a larger one, and try a spoon or a bead too. Compare with the idea that only some impacts trap air [2].
Do this with a grown-up nearby, and do not put your head or ears into water to listen. If you want to go further, read the carp study [5] and the bass abstract [7] yourself. Then ask: what experiment would show whether a rattle changes what a fish does?