Can I record sound until silence OR a maximum length of recording?

Looking at detecting sound until some silence occurs , I arrived at the command rec recording.flac rate 32k silence -l 1 0.1 3% 1 3.0 3%. I realize my specific use would be somewhat different: I do want to record until some silence is detected, but I also want an upper limit, say 10-15 seconds, of how long the recording will go on before moving on. I can just prepend a timeout 15s command, which would give me a maximum speech time of (15 seconds - leading silence, which will vary), but is there some way to tell sox I only need the first x seconds of a recording, which would give me a maximum speech time of 15 secs regardless of leading silence?