Reflective areas are those places in your rehearsal room where the sound bounces off. Hard sufaces such as tiles and stone walls are typically very reflective materials.
It is possible to deaden some of the reflective areas in your rehearsal room. If you have ever been to a recording studio, or dedicated rehearsal room, you may have noticed that the walls were covered in some kind of material to eliminate the relection of the sound.
Too much relection of the sound will make the room echoy and it may be less enjoyable to play in a room as such. Deading all the refective sounds in your rehearsal room will result in a dead sound, but when you are using electronic reverbs this may not be such a problem. Ideally you should strive to keep some of the reflection to keep the sound from being natural.
There are many dedicated products on market for you to choose from to create the ideal rehearsal room, however, when you think about what you are trying to achieve, you may able to improvise a bit with various materials and get similar results in a simpler (and often cheaper) way.
Using Carpet,Cardboard and Wood:
Observe the walls or your rehearsal space and put some carpet on the wall. You can get the carpet onto the wall by using screws or glue and any method which will keep the carpet firmly fitted to the wall. Carpet will absorb the sound and lessen the refection. Cardboard does have similar characteristics as carpet, it may not absorb the sound completely but it will lessen the reflection of the sound, which is part of your goal. You may be able to find large carboard boxes, fold them into one and use them as a panel. Use double sided cardboard, which makes it easy for it to stand up against the wall.
Using wood is also a good idea, wood will aborb the sound as well. You may be able to find pieces of wood and use them as panels (similar as with the cardboard) and arrrange them around some of the walls of your rehearsal space.
As you do some of the the above, keep some areas free for the sound to bouce off, to remain some refection, which will give you a more natural sound.
Sound Levels and Treated Rooms:
You may find, after you have treated your room, that your band does not have to play that loud for each instrument to be heard. Working with the sound (and size) the room is always a good habit, try it. If you use different rooms for rehearsing, try to tread the rooms differently so you can observe the differences in sound.
Hope to catch you soon again,