Man, back in the day of the 80's and early 90's I remember when SPL was a specific track on a IASCA cd and it was measured that way.
Now it's with specific frequencies?
When did this start and why?
Is that what is called burping?

 

'Burping' was made popular in the early-ish 90s by competitors such as Mark Fukuda. Mark used Flashdance for his #s but added a momentary switch to his podium so the Blazer was quiet until the part of the song came on that he used.

Hmm, the switch to 'tones' from 'music' is tougher to pinpoint.. dBDrag lifted the ban on pure tones in 1996 or so because a lot of the "songs" in use basically had straight tones in them anyway - stuff like Techmaster and DJMagic Mike..

 

that helps.
Thanks.