#background_signal__background  extraneous signals that can be confused with the phenomenon to be observed or measured; "they got a bad connection and could hardly hear one another over the background signals"
  supertype:  #interference__noise__disturbance  electrical or acoustic activity that can disturb communication
  subtype:  #background_noise__ground_noise  extraneous noise contaminating sound measurements that cannot be separated from the desired signal
     subtype:  #surface_noise__surfacenoise  noise produced by the friction of the stylus of a record player moving over the rotating record
  subtype:  #background_radiation  radiation coming from sources other than those being observed

No statement uses or specializes #background_signal; click here to add one.