This superpower is known as "Enhanced Hearing."
- May be more sensitive to loud sounds.
- Noise can limit the distance of the users hearing range or ability to detect minor sounds.
- Inaudibility and Silence Manipulation (which are other superpowers) will make this power useless.
- Too many conversations around the user may make it difficult to find the right one to listen to unless if they have a method to easily distinguish them.
- Exact sensitivity and range of hearing varies by individual.
But in reality, the farthest ranges of human hearing are considered to be 20,000 kHz. While a human’s best range is better than many animals, it pales to the hearing range of cows, cats, ferrets and several other creatures.
Guinness World Records page for hearing.
This means Daredevil's hearing abilities are very unrealistic when you consider the additional noises and sounds in Hell's Kitchen.
Daredevil's sense of hearing is so acute that he can detect an acoustic pressure change of 1 decibel at a pressure level of 7 decibels (whereas the lowest threshold for average human hearing is 20 decibels).
This enables him to hear a person's heartbeat a distance of twenty feet, or people whispering on the other side of a standard sound-proof wall.
The exact workings of Daredevil's version of the "proximity sense" are somewhat mysterious. According to one theory, Daredevil's brain has several regions which are able to sense consciously that portion of the electromagnetic spectrum that his brain constantly generates.
He is able to resolve the image of an average flagpole (a three-inch cylinder) at a distance of over 80 feet.
Note: There are fanmade comic book scenes about Daredevil's flagpole usage. They are mostly for fun.