Recording rtl_fm output

Something I am doing is not quite right. The following example works almost perfectly but please read on. rtl_fm -f 88.3e6 -M wbfm -s 215000 -r 44100 - | aplay -r 44.1k -f S16_LE The audio from the sound card is nearly excellent. To record this stream, I do the following: rtl_fm -f 88.3e6 -M wbfm -s 215000 -r 44100 testfile.bin I get a file so it would appear that the following should sound just like the stream I am listening to using the pipe in the first example. aplay -r 44.1k -f S16_LE testfile.bin The pitch of the audio is fine but instead of almost dead silence between words, there is a lot of hiss and distortion. In theory, I should hear the same mostly noiseless audio I hear in the first example when playing from the file. This is really not a DSP issue but maybe I have saved the audio as unsigned and am trying to play it signed which would preserve the pitch but be a cause for a lot of distortion. Besides, it is apparently signed when piped in to aplay. I am mystified. Thanks. Martin McCormick