Some easy DIY Self-Powered devices ? ( some can power a home )

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  odd,  I thought that a quite loud very high-pitched constant hiss( doubt anyone hears ringing ) that I only hear at home,  is tinnitus,   since I often still hear it,  if I plug my ears with noise-dampening earplugs( foam-rubber type )
   
   this morning though, I noticed that if I covered my ears with my hands,   that I could no longer hear it, and also,  it was as if someone was testing different tones of this loud very high-pitched constant hiss

  this afternoon though,   the situation seems to have returned to it's normal description,  I can still hear it when I put in noise-dampening earplugs( foam-rubber type ), and am not sure that covering my ears with my hands while also having the earplugs in,  makes any difference

  unless it's something malfunctioning in my flat,  or somewhere
     also,  I often read that high-frequency sound like this can not get through concrete, but from experience with other things,  I'm not sure thats a true statement