Home studio Help.

Hello everyone, I have recently started my home studio, I have 2 rooms one is 12' x 12', which will be the control room, the other is a 23' x 12', which is intended to be my recording area. Both rooms have a 9 foot celling. The walls are made out of Concrete Block. The room that is 23'x12' I removed all the windows it had and sealed them with concrete blocks as well so it stops all the sound. I will post pictures of both rooms and their current status soon. Since the studio is in my house, it is located next to an extremly busy main street and I have a supermarket across the street, this is to the back of the house these 2 rooms are to the front and in the recording are barely any sound from the outside is heard. Now my main concern is that the room that will be come my recording room, the one that is 23'x12' is extremely bright. It seems that what I have a is a lot of flutter. Any help would be appreciated thanks in advance,

You need acoustic treatment....