# Also convert the raw audio on-the-fly to the GSM format using 'sox', so that
 # we can play it back to the user right now.
 open( $fh, "|/usr/bin/sox -t raw -r 8000 -s -b 16 -c 1 - /tmp/recording.gsm" );
 #                             |      |    |  |    |   |   |
 #                             |      |    |  |    |   |   '-- Write to this file
 #                             |      |    |  |    |   '-- Read from STDIN
 #                             |      |    |  |    '-- Mono Audio
 #                             |      |    |  '---- Samples are words (a word is 2 bytes = 16 bit audio)
 #                             |      |    '---- The audio is signed (32766..-32766)
 #                             |      '---- The sample rate is 8,000 samples/second
 #                             '---- The input format is SLIN, which is 'raw' audio