I do some voiceover work at home and have been experimenting with mics for a while.
I've had background noise with 5 of the 7 Mic I've tried. And it's not the same noise. The spectrum for each is very different.
The bad ones sound as bad (or worse) than a $5 cheapo PC mic. The bad ones range in price from $30 to $100.
I guess I could be getting bad mics, but this is just really surprising.
WHAT I HAVE TRIED
Update: forgot to mention I disabled AGC (sometimes called Mic Boost) before I started all of this.
I reduced room noise
- My PC has a SSD drive and the fan doesn't normally run (I can't hear it or feel vibration in the PC)
- I turned off the lights (Flourescent overhead), the CRT (leaving two Lcs on).
- Turned off the secondary computer (server).
- Changed Mic Properties, Advanced, from CD Quality to DVD and even Studio quality. Made little difference (and in fact the vocal s got quieter in the Studio quality but the noise didn't get much quieter)
- I have tried another room in the house with no devices (using a laptop on battery power (hey, could be weird ground-loop problem)
- This all made a tiny difference.
Mics have tried:
somewhat expensive D.R.K. MXL Mic and it has noise. (uses a 3.5m jack)
a CAD U1 mic (cheaper but well rated) and it has noise (see this question (uses a USB connection).
What worked well is a rather generic Logitech USB Mic (and also, a $20 generic (but powered) Radioshack mic (no sample of that)