this is yet another microphone noise problem question. I've checked http://askubuntu.com/search?q=microphone+noise and they are not for latest Ubuntu 13.04.
I've Dell Inspiron 7520 with
List of CAPTURE Hardware Devices **
card 0: PCH [HDA Intel PCH], device 0: CONEXANT Analog [CONEXANT Analog]
Subdevice #0: subdevice #0
I've already changed default sample rate to 96,000, already added tsched=0 and default-fragment-size-msec to 5.
Here is sample of sound recorded with arecord in -r 8000 and -r 96000:
As you can hear from the above files there is constant noise in background. This is not present in Windows. In alsamixer I've microphone boost selected by two up keystroke which puts it to 28 and internal microphone to full. This is the best setting I've found so far which puts my sound loud enough and background noise to minimum. Still it would be best if I can get rid of this noise.