The window-mounted AC units are often louder than their through-the-wall cousins. This is largely due to the fact that window AC units are being exposed, whereas the through-the-wall air conditioners are hidden in the walls that help to reduce any sound the unit may produce. However, even the window-mounted units are still pretty quiet. In the customer reviews, you can find the information that one of the main advantages of Arctic King air conditioners is how quiet they are, regardless of what type you chose.