$ ffmpeg -ss 5 -t 10 -i IronMan.mkv -f wav -ar 44100 somefile.wav
ffmpeg version N-41550-gddece75 Copyright (c) 2000-2012 the FFmpeg developers
  built on Jun 14 2012 09:56:58 with gcc 4.7.0 20120505 (prerelease)
  configuration: --prefix=/usr --enable-gpl --enable-libfaac --enable-libfreetype --enable-libmp3lame --enable-libtheora --enable-libutvideo --enable-libvo_aacenc --enable-libvorbis --enable-libx264 --enable-nonfree --enable-version3 --enable-x11grab
  libavutil      51. 58.100 / 51. 58.100
  libavcodec     54. 25.100 / 54. 25.100
  libavformat    54.  6.101 / 54.  6.101
  libavdevice    54.  0.100 / 54.  0.100
  libavfilter     2. 79.100 /  2. 79.100
  libswscale      2.  1.100 /  2.  1.100
  libswresample   0. 15.100 /  0. 15.100
  libpostproc    52.  0.100 / 52.  0.100
Input #0, matroska,webm, from 'IronMan.mkv':
  Metadata:
    creation_time   : 2008-10-22 06:43:30
  Duration: 00:01:48.50, start: 0.000000, bitrate: 4141 kb/s
    Stream #0:0: Video: h264 (High), yuv420p, 1280x720, SAR 115:87 DAR 1840:783, 23.98 fps, 23.98 tbr, 1k tbn, 47.95 tbc (default)
    Stream #0:1: Audio: aac, 48000 Hz, stereo, s16 (default)
File 'somefile.wav' already exists. Overwrite ? [y/N] y
auto-inserting filter 'auto-inserted resampler 0' between the filter 'Parsed_anull_0' and the filter 'aformat'
[auto-inserted resampler 0 @ 0x2ac3e00] chl:stereo fmt:s16 r:48000Hz -> chl:stereo fmt:s16 r:44100Hz
Output #0, wav, to 'somefile.wav':
  Metadata:
    creation_time   : 2008-10-22 06:43:30
    encoder         : Lavf54.6.101
    Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 44100 Hz, stereo, s16, 1411 kb/s (default)
Stream mapping:
  Stream #0:1 -> #0:0 (aac -> pcm_s16le)
Press [q] to stop, [?] for help
[matroska,webm @ 0x2ac6120] File is broken, keyframes not correctly marked!
size=    1918kB time=00:00:10.01 bitrate=1568.8kbits/s
video:0kB audio:1918kB global headers:0kB muxing overhead 0.002342%