When sound waves are travelling through a room, the direct sound is picked up first by a person as well as by a microphone; afterwards the reflections from surfaces, such as walls, the floor and the ceiling are audible. This ambient sound gives an impression of the room size – is it a small or large room or even a concert hall? A sound signal free of reflections or reverberation sounds unnatural, as it does not exist in nature.
Nevertheless it is the goal to record a signal that is free of ambient sound and reflections – no matter if speech, singing or instruments. If the signal was recorded with ambient sound, it cannot be removed afterwards. Reverberation should be added in the post production, giving the opportunity to choose the desired sound.
What does this mean for home recording and podcasting? The most important rule is: the closer the mic moves to the sound source, the less ambient noise is picked up and the higher the sound level. Additionally unwanted noise, such as the noise created by a computer fan or the playback music coming from the headphones, is reduced as well.
The boost in low frequencies caused by the proximity effect should be considered when placing the mic very close. The mic should always be aimed directly at the sound source as the level becomes lower when the mic moves away. The microphone should also not be placed too close to a wall. The reflections from this wall are picked up as well and they degrade the sound quality. Be aware that also simple sheets of paper that you might need to read the lyrics can reflect sound.
The recording room should acoustically be as “dead“ as possible. This means avoidingconcrete walls and floors as well as windows. A square shaped room with a tiled floor and concrete walls is surely one of the worst environments for recording. A carpet helps reducing the reflections. Book shelves, curtains at the windows or heavy drapes help to “deaden” the room. Acoustic foam is certainly the best but also a very costly solution. A mattress on the wall or a pile of blankets in a corner of the room is a good starting point.
The room should also be as “quiet” as possible. Higher quality condenser microphones pick up even the quietest signal. A computer is very often a disturbing factor in home recording. A silent processor fan and power supply should be self-evident. A passively cooled graphic card is also recommended. A decoupled hard drive minimizes chassis vibrations and reduces the noise as well. If the noise cannot be avoided, make sure to follow the already mentioned rules to keep the microphone as far away from the noise as possible and not to aim the mic into the direction of the disturbing sound.
