When you clap your hands in a bedroom you will hear the sound reflections off the walls and other reflective surfaces. These reflections can make a vocal recording or any other microphone recording sound awful and will also effect the accuracy of your mix when mixing from speakers. This can be corrected using acoustic foam to acoustically treat the room.
You can use special foam panels which will help control the acoustics of a room. Placing them around the room will reduce the amount of sound wave reflections from walls or ceilings by absorbing some of the sound to get a clearer and more controlled sounding room. This is important when you want to record using a microphone because reflections from surfaces bounce back to the microphone and effect your recording. I recommend you do your mixing in an acoustically treated room so you are hearing the sound from the speakers and not the reflections off the walls which can prevent you from making a good mix.
Acoustic foam has sound absorption properties and is used used in most recording studios and rehearsal studios to control the acoustics of the room by absorbing the reflections of sound as they reach the walls and ceiling.
These special foam panels are usually come the shape of a square and the most common sizes are 500mm x 500mm (50cm x 50cm) and 300mm by 300mm (30cm x 30cm) but they are also available in other sizes. When you want to do recording with a microphone or mix using your speakers you will need to use these sound absorption panels to get the best possible acoustic environment.
There are several common types of foam panels which you can buy to acoustically treat your room with.
Often overlooked in small home studios a bass trap will help by absorbing the lower end sounds. Bass traps are effective when placed in the places walls meet. Placing a bass trap down each corner of your room will help reduce the amount of deeper tones being reflected.
EGG CRATE (PYRAMID FOAM
These foam panels have small pyramid shaped extrusions which absorb sounds and they reflect sounds a lot less than a flat surface. Any sound waves reflected from these foam panels will be sent in different directions.
WEDGED ACOUSTIC FOAM
Wedged acoustic foam is the most aesthetically appealing type of foam panel and is also good at sound absorption. These panels are most effective when placed perpendicularly to the area the sound is being reflected from. To explain what I mean by this the wedges must be pointing vertically if the sound waves are horizontal and horizontally if the sound waves vertical.
FLAT ACOUSTIC FOAM
Flat acoustic foam has sound absorption properties but will reflect sound waves in the same direction as the surface they are on. Flat acoustic panels are good to use in combination with other panels but not on their own.