It's a somewhat similar reaction to our aversion to certain frequency noises; just with a different result.

Take "horror" movies for example; you know how a vast majority have violins/violas/etc playing a certain cacophonous note, gradually building in intensity until a climax (right before jumpscares for instance.) Or a monster will have a somewhat high-pitched "shriek."

The sounds are typically (not always) designed pretty similar to the frequencies emitted by a crying baby, which we're "hardwired" to seek out/identify.

A majority of folks are moved by the sound of a wailing babe in some form, whether it be general irritation to invoking sympathy. We're just at a stage where we can resist the urge to immediately act upon it, but if you can hear, you're still succinctly aware it's happening.

Beavers have a few other habits that drive them to dam it; most notably the habit of eating the bark/limbs of trees, and piling the less-nutritious, "dead" bits of wood into piles. Pack those piles with mud/sediment, as they grow it becomes relatively structurally sound. Very similar to "primitive" human dwellings, how quaint.

Eat bark in one area for long enough, you'll have to travel out further from home (safety), for fresh bark; they're not exactly graceful on land, but nimble as fuck underwater. Very, very few of their predators stand a chance in Hell catching them in water.

Let evolution and learning do its thing for a few centuries, and beavers realized packing their leftovers and mud around a certain sound - uneven, burbling water - it'll stop, and the water that was running to make said sound starts to well up/flood the area it was coming from, giving it more range and easy escape routes to forage over wider areas.

A side effect of those piles is they typically end up raising slightly above water level, leaving a pocket of well-insulted air inside. As the structures settle and become more structurally sound, the area becomes surrounded by water on some or all sides, which makes it far easier to escape a predator while out and about - they are rodents after all, and rodents are the meatballs of nature in terms of the food chain. Think of it as building a studio apartment with an entrance only accessible through a moat, and you're one of only a few world-class swimmers in the neighborhood.

Wood also floats pretty well, and due to further adaptions - namely having two sets of lips, one in front and one behind their iron-reinforced buckteefs - it's extremely efficient for transporting said wood/food back home.

Unlike most other rodents, this relative safety of dam life finds them being more "monogamous," having much smaller litters compared to their rodent brethren, and they actually spend the time/energy to raise/teach their offspring instead of always worrying about getting eaten. Dam building is instinctual to a point, but practice makes perfect; you can tell the difference between a youngin's dam and an elder beaver's dam.

Another thing to note; you know how beavers chew down trees? They're not eating the trees' innards like one would think; most the time, they're bringing the good stuff too high to reach - young, tender, nutritious limbs - down to them. The innards of most trees are akin to eating nothing but celery, while the bark/newly formed limbs are like celery with ranch or peanut butter; more nutrient dense. Granted they have to basically "chew their cud" the hard way to get the most out of it, it's still better than the hard, "dead" innards. They also seem to know exactly where to chisel away at said trees to get them to fall towards a body of water for a quick escape in case the sound attracts unwanted attention^_^