arecord, convert: edit pages (#12644)

Co-authored-by: Sebastiaan Speck <12570668+sebastiaanspeck@users.noreply.github.com>
Co-authored-by: K.B.Dharun Krishna <kbdharunkrishna@gmail.com>

pages/linux/arecord.md

@@ -22,3 +22,7 @@
 - Allow interactive interface (e.g. use space-bar or enter to play or pause):
 
 `arecord --interactive`
+
+- Test your microphone by recording a 5 second sample and playing it back:
+
+`arecord -d 5 test-mic.wav && aplay test-mic.wav && rm test-mic.wav`