Hovering Rhythm

*Helicopter ambience only, No music, no melody, no instruments, no vocals, A large helicopter hovering nearby in the background: deep rhythmic rotor-blade WHUP-WHUP-WHUP-WHUP, heavy spinning blades cutting through the air, low engine rumble, subtle Doppler movement, occasional blade flutter and wind turbulence, Realistic outdoor field recording, slightly distant but powerful, continuous hypnotic rotor rhythm, No cinematic score, Pure helicopter soundscape, *