How to remove ffmpeg metadata "software lavf55.7.100"

I'm using ffmpeg to extract audio from video files, then process the audio and cut it into smaller clip. But when i use ffmpeg to do the extraction, it adds a metadata "software lavf55.7.100" into my audio file, which screws my indexing of cutting. How can i get rid of this?
In attached picture, in the middle "Metadata: ISFT : Lavf55.7.100"
The string that i'm using is: ffmpeg -i steve.mp4 -map_metadata -1 steve14.wav

I solved it by opening up the file in hex reader and found the location and length of this tag