Helicopter propeller sound
Source: helicopter.mp3 supplied by the mod author for this replacement.
No original creator or external license information accompanied the recording.
Original recording SHA-256: d208d09fe4488c3509389222eae75720e502b4e6ec2f9f8c6b26021316ece154
Adaptation: opening 0.65 seconds and final 2 seconds removed from the supplied
recording; steady rotor section converted to mono 44.1 kHz Ogg Vorbis,
with a 0.25-second wrap crossfade for uninterrupted positional looping.
The original recording is preserved in tools/audio-sources/helicopter-user-provided.mp3.

The earlier CC0 Propeller (Cartoon) Loop by Mish7913 is no longer used by the
helicopter. Its original remains in tools/audio-sources/propeller-cartoon-loop-original.ogg;
its source and attribution are preserved in the historical development notes.

