This sound effect was recorded with high quality sound equipment and comes from a sound library called EMF which is pack of 216 high quality audio files with a total length of 378 minutes. In this library you'll find different sci-fi sound effects recorded with special microphones that changes electro-magnetic field into the sound. You can use this sound for free, and if you need a whole package of ambients you can support my work and get it for 40$ here: <a href="http://soundholder.com/product/sound-library-electromagnetic-field/" rel="nofollow">http://soundholder.com/product/sound-library-electromagnetic-field/</a> Also here's a 10% discount code for all freesound users, just type : freesound in discount window. Enjoy!