Itaewon is a noisy place but I don’t think it is any louder then other party areas in Korea like Myeondong which is my opinion is much noiser:

Think it’s a little loud outside when you wander off Yongsan Garrison into the local neighborhood? Good call.

The sidewalk in front of Itaewon’s Crown Hotel is the loudest place in the country, according to a South Korean government agency.

The Environmental Management Corp. installed 62 automatic noise measuring devices in South Korea this year, 15 of them in Seoul. The machines recorded daytime noise in front of the Crown Hotel at 77.5 decibels and nighttime noise at 75 decibels — higher than the normal daytime environmental noise standard of 65 decibels and the normal nighttime standard of 55 decibels.

A factory usually has a noise level of 75 decibels.

The sidewalk in front of Itaewon’s Kookmin bank, near the Itaewon fire station, also made the list of the noisiest spots in Seoul, with a daytime recording of 70.4 decibels and a nighttime recording of 68.1 decibels. [Stars & Stripes]

This is probably why Myeongdong and other areas like Dongdaemun didn’t make the list:

About 1,500 noise monitors are scattered around South Korea, but only a handful automatically record noise levels 24 hours a day. Officials don’t regularly keep readings from the manual noise monitors, which is why some busy spots like Seoul Station — which doesn’t have an automatic noise monitor — might not have made the list of Seoul’s loudest places.