Here's a few portable voiceover booths:
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www.harlanhogan.com/port ··· le.shtml»
www.realtraps.com/p_pvb.htm»
blogs.oreilly.com/digita ··· oth.htmlGet yourself as close as reasonable to the mic, and as far away as possible from the noise sources. Distance and separation are your friend when it comes to noise. The booth might cut the noise down a bit, but not completely.