$ ffmpeg -i foo.wav -af silencedetect -f null - 2>&1 | awk '/silence_end/ { list = list "," $5 } END { gsub(/^,/,"",list); print list }'
481.541,685.14,862.642,1279.63,1293.61,1315.21,1341.75,1411.74,1415.68,1430.96