A paging system in a large industrial complex is making this bird chirping noise or it sound like a tea kettle boiling, but more like a little bird. The sound is mostly random except the customer says its usually after a page, but it would not do it for me when I was paging, only one time and it lasted for 5 seconds or so.. The chirping is system wide and the speakers are a mix of bogan 70v powered by bogan amps and bogan 24v self amplified speakers in outlying buildings... Basically, I couldn't troubleshoot it because i couldn't duplicate the sound reliable enough to narrow it down... but I did punch down the paging feed to the other building on a different pair in the underground cable, hoping that maybe that was the problem... Has anyone heard this noise on a paging system before and can give me a hint what to look for that could be causing it? the paging audio is also going through a viking feedback eliminator before it goes to any amp or speaker.