Add feature to audio recording bash script (ring buffer)

I have a simple bash script that uses arecord to record 4 seconds of audio to a file then it copies the file to another file for processing by another program. I would like someone to help me with add one or two lines that make it so it continually record half a second and then adds it to the file while deleting the first half second. Or if it makes more sense we can continuously update 8 half second files and concatenate them into one file. Attached is the existing bash script for reference. I think FFMPEG is the tool for the job but anything is fine.