ffmpeg video encoding has no audio

When I convert any video in ffmpeg – e.g. mp4 to mkv, mkv to mkv – I lose audio for some reason
here are the parameters I originally used:
ffmpeg -i input.mkv -vf scale=640x480 -vcodec libx264 -profile:v main -level 3.1 -preset medium -crf 23 -x264-params ref=4 -acodec libvorbis -movflags +faststart output.mkv

I tried mkv to mkv with the same paramaters and then I deleted most of the things to get this:
ffmpeg -i input.mkv -vf scale=640x480 output.mkv

there is still no audio even when simplifying this much
can somebody help please