This contains about every sound that was included in BeOS 4.x. They are normally in the AIFF format and have been converted to WAV for convenience and playability on modern devices.

Except for BeBeep, BeStartup, and RU.N+, all of the other sounds need to be installed via installing the optional components.

Admitably though, you're probably just here for 12StrStart, which is infamously known for being the sound incorrectly attributed as the shutdown sound for Windows Whistler/XP beta builds (none of the XP beta builds ever had BeOS sounds, let alone that one).

These sounds were ripped from BeOS 4.0. Ripped by BF10.