പങ്കാളിത്ത ഓഡിയോ

Generate a clean SOS knock signal: three short knocks, three long knocks, three short knocks. Short knocks should be sharp and 0.25 seconds long. Long knocks should be deeper and around 1 second long. Use a hollow metallic surface, like a pipe or vent. No background noise, no reverb, clean and isolated sound.