Add 'drone' audio sound

[nfreear]

..

• Example :~ https://freesound.org/people/tec_studio/sounds/353976/;
• Use :~ https://developer.mozilla.org/en-US/docs/Web/API/HTMLElement/animationiteration_event;
• See :~ https://developer.mozilla.org/en-US/docs/Web/API/AnimationEvent;

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Drone.wav

• MP3 preview :~ https://freesound.org/data/previews/353/353976_1431924-lq.mp3;

-0.63 dB // -00:10:853

• By: T.E.C. Studios / TEC Studios USA (Joel Graham) / tec_studio;
• September 11th, 2016
• License: This work is licensed under the Creative Commons 0 License.
• Type: Wave (.wav)
• Duration: 00:33:484
• Filesize: 11.3 MB
• Samplerate: 44100.0 Hz
• Bitdepth: 32 bit
• Channels: Stereo
• Pack: TEC Drones and Phrases

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