if you are triyng to grab (to record) the screen (the video) and the sound (the audio) by ffmpeg or by avconv and there no speaker sound (and only sound from microphone), then you should record the 'monitor', not 'default'/'pulse'/'hw':

1. Find the name of the 'monitor':
Code:
 pactl list sources | grep analog-stereo.monitor
Name: alsa_output.pci-0000_00_1b.0.analog-stereo.monitor
or
Code:
 echo $(pactl list | grep -A2 '^Source #' | grep 'Name: .*\.monitor$' | awk '{print $NF}' | tail -n1)
alsa_output.pci-0000_00_1b.0.analog-stereo.monitor

2a. Audio:
Code:
 ffmpeg -f pulse -i alsa_output.pci-0000_00_1b.0.analog-stereo.monitor  alsa-output_analog-stereo_monitor.wav
or
Code:
 avconv -f pulse -i alsa_output.pci-0000_00_1b.0.analog-stereo.monitor  alsa-output_analog-stereo_monitor.wav
2b. Audio and video:
Code:
 ffmpeg -f pulse -ac 1 -i alsa_output.pci-0000_00_1b.0.analog-stereo.monitor -f x11grab -r 24 -s 1920x1080 -i :0.0 -vcodec libx264 -crf 22 -acodec libmp3lame -ar 22050 -ab 63k grab1.mp4
or
Code:
 avconv -f pulse -ac 1 -i alsa_output.pci-0000_00_1b.0.analog-stereo.monitor -f x11grab -r 24 -s 1920x1080 -i :0.0 -vcodec libx264 -crf 22 -acodec libmp3lame -ar 22050 -ab 63k grab1.mp4