The barred owl is a powerful vocalist, with an array of calls that are considered "fantastic, loud, and emphatic". Calls probably carry well over 0.8 km. Its usual call is a series of eight accented hoots or the "typical two-phrase hoot" with a downward pitch at the end.
Due to its best-known call, the barred owl is sometimes colloquially referred to as Old Eight-Hooter. Another call type is the "mumble", a grumbling, slurred, and subtle an up-and-down "twitter" calls at a high pitch. When agitated, this species will make a buzzy, rasping hiss about three times in three seconds, repeating every 10–30 seconds, and will click its beak together forcefully.
The voice of the two sexes is similar, but the female has a higher-pitched voice with longer terminal notes. While calls are most common at night, the birds do call during the day as well, especially when provoked by human playback or imitation. They are more responsive than any hawk in the east to playback of calls of their own species.
The barred owl is noisy in most seasons but peak vocalization times for barred owls tend to be between late January and early April. Two seasonal peaks in vocalizations, one right before breeding and another after the young have dispersed, with peak vocalizations on nights with extensive cloud cover. Peak times for vocalizations are between 6:00 pm and 6:00 am, with the least frequent vocalizations around mid-afternoon.