If you want to do an easy test- download a frequency generator app on your smart phone and do a frequency sweep at a moderate volume level. I use Tone Generator Ultra and it does tones, musical notes (showing the frequency of what is being produced, as well as producing the note), wave (sine, square and saw tooth) and when using the sweep function, you can set the upper and lower frequency limits, as well as the speed of the sweep. If you hear chirping or anything other than a clean sound, your tweeters should be fine.
If the volume control was at 35/80 when the sound occurred, they should be fine- that's far from the maximum output of the AVR.