This is actually more complex than it seems at first. There are at least two questions here – one is what carpet is recommended for the recording or audio mastering area, the other is what carpet is recommended for the control room or mastering suite? Conventionally the answer has been for a long time that no carpet is recommended – just bare wood or laminate flooring. One reason for this is that carpet quickly wears out or becomes ‘old’ looking, particularly in the control room under the engineer’s chair, and in areas where equipment is loaded or stored. These areas should not be carpeted, for purely practical reasons. The other areas can be carpeted if you wish. Research has shown that carpet is a great absorber of high and high-mid frequencies. Compared to other forms of absorption it’s quite cheap too. But carpet has little or no effect on low frequency sounds – it’s too thin even with thick heavy carpet. So a room that is carpeted will have a lot of absorption at high and high-mid frequencies, a little at mid frequencies and none at low frequencies. At this point, other measures should be taken. One is to reduce the area covered by carpet and use a thinner carpet. The room will be livelier, and there will be a better balance of frequencies. The other is to provide low-frequency absorption, which can be done using proprietary modules, or by constructing panel or membrane absorbers. You can actually make a low-frequency absorber out of carpet. Hang the carpet on the wall supported by a wooden batten spacing the carpet 2 – 4 inches away from the wall. Now, fix similar battens all around the edges of the carpet, and nail the carpet down. Such an absorber will still have more high and mid absorption than low, but it’s better than just carpet alone, and it can be balanced out with other acoustic treatment methods elsewhere in the room.