1. Effect->Amplify
  2. Effect->change speed
  3. Fiyle->export

but the exported file is really big

pet@cow:~$ man lame
pet@cow:~$ lame what_is_linux.wav w.wav
LAME 3.98 32bits (http://www.mp3dev.org/)
CPU features: MMX (ASM used), SSE (ASM used), SSE2
Using polyphase lowpass filter, transition band: 16538 Hz - 17071 Hz
Encoding what_is_linux.wav to w.wav
Encoding as 44.1 kHz j-stereo MPEG-1 Layer III (11x) 128 kbps qval=3
    Frame          |  CPU time/estim | REAL time/estim | play/CPU |    ETA
 11833/11833 (100%)|    0:25/    0:25|    0:27/    0:27|   12.300x|    0:00
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
   kbps        MS  %     long switch short %
  128.0      100.0       100.0   0.0   0.0
Writing LAME Tag...done
ReplayGain: +22.7dB
pet@cow:~$ ls
Desktop  edit_private.sh  edocs  github  index.html  index.html.1  kdocs  save_private.sh  tinylion  tmp  what_is_linux.wav  w.wav  xx
pet@cow:~$ du -sh w.wav
4.8M	w.wav
pet@cow:~$

the output file is small but the quanlity is just as good.

mix voice and music

http://wiki.audacityteam.org/wiki/Creating_a_simple_voice_and_music_Podcast_with_Audacity

it is easy to use effct->fade in to add a startup music for my speech

Use Ctr+C Ctr+v and fadeout fadein cut paste, I get things mixed together nicely, and it is so easy.

I do not need to foolishly applify my voice everytime!!!