Pop Filter - A screen placed in front of or over a microphone that reduces the effect of speech plosives and wind.
Speaking or singing directly into a mic often creates unwanted sibilance (an exaggeration and distortion of high-frequency "S" sounds), pops from plosive sounds (words with initial "p's," and "b's"). Pop filters are designed to reduce the pops from these plosive sounds.
How much do they cost ? Well, some here have made their own from cross-stitch hoops and nylon stocking . . . then try to figure out how to mount it to the mic or stand. You can buy one from musicians friend at musiciansfriend.com. $19.99 for a 4" diameter and $29.99 for a 6", so making one seems more a challenge than a savings. To me, my time is worth something.
If you're using a handheld mic, a good quality foam windscreen will serve a similar purpose, although maybe not quite as well.
Is it necessary ? Depends on whether you sing close to the mic and are having plosive problems. Good vocalists know how to work the mic and angle their head when a plosive comes around. Watch a good singer on TV sometime. All that head jerking and those head angle changes aren't just for show.
Hope that answers your questions.
Regards,
PAPicker
[This message has been edited by PAPicker (edited 04-08-2000).]