Poor audio quality can kill a slickly finished video. Viewers or listeners will find such a result extremely unprofessional. They may not understand what was said in the recording. It follows that the sound quality should be the best possible.
Since outside sound can interfere with the audio quality, external sound waves must be stopped from entering the record room. To do this, the room should be encased in dense materials. Ideally, this should be done during the building construction stage. If this is not possible, there are a couple of other methods which deliver near identical results.
A good voiceover room must not only block outside noise, it must also absorb stray sound waves. The rest should be diffused. Buying a premium quality professional microphone helps. To prepare a premium quality voiceover room, use plaster to cover the walls and not a drywall. There should be no windows in the room. Best places to record sound could be unconventional. To give an example, a walk-in closet makes an excellent audio recording spot. For complete silence, purchase acoustic foam and plaster the voiceover room with it. Put in a few acoustic panels to cover the room corners.