$ ffmpeg  -i ~/foo.3ga -map 0:0 -af "aconvert=flt:auto" -y foo.wav
ffmpeg version 1.0 Copyright (c) 2000-2012 the FFmpeg developers
  built on Oct  7 2012 17:13:52 with gcc 4.6 (Ubuntu/Linaro 4.6.3-1ubuntu5)
  configuration: --enable-debug --enable-ffplay
  libavutil      51. 73.101 / 51. 73.101
  libavcodec     54. 59.100 / 54. 59.100
  libavformat    54. 29.104 / 54. 29.104
  libavdevice    54.  2.101 / 54.  2.101
  libavfilter     3. 17.100 /  3. 17.100
  libswscale      2.  1.101 /  2.  1.101
  libswresample   0. 15.100 /  0. 15.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/home/ddurham/foo.3ga':
  Metadata:
    major_brand     : 3gp4
    minor_version   : 0
    compatible_brands: isom3gp4
    creation_time   : 2012-10-07 15:24:51
  Duration: 01:09:44.02, start: 0.000000, bitrate: 124 kb/s
    Stream #0:0(eng): Audio: aac (mp4a / 0x6134706D), 44100 Hz, mono, s16, 123 kb/s
    Metadata:
      creation_time   : 2012-10-07 15:24:51
      handler_name    : SoundHandle
Output #0, wav, to 'foo.wav':
  Metadata:
    major_brand     : 3gp4
    minor_version   : 0
    compatible_brands: isom3gp4
    encoder         : Lavf54.29.104
    Stream #0:0(eng): Audio: pcm_s16le ([1][0][0][0] / 0x0001), 44100 Hz, mono, s16, 705 kb/s
    Metadata:
      creation_time   : 2012-10-07 15:24:51
      handler_name    : SoundHandle
Stream mapping:
  Stream #0:0 -> #0:0 (aac -> pcm_s16le)
Press [q] to stop, [?] for help
size=  360380kB time=01:09:44.02 bitrate= 705.6kbits/s
video:0kB audio:360380kB subtitle:0 global headers:0kB muxing overhead 0.000012%
$