What is this scary siren

[mgear]

Wow I need to use the restroom now. http://youtube.com/watch?v=P5kVLDm8iAY

[Trey]

Sounds like a T-bolt 1000T starving for power to me.

[Nelso90]

Man that sounds cool!

[kswx29]

That sounds like a siren used to signal the end of the world.

[Archon]

Sounds like a 4/5 port TB on lowest tap

[ThunderboltFreak]

Wow, that Tbolt goes up in tone a couple of times in the video.

[loudmouth]

the pitch deffitly shifted up a littel kinda of werid. nice sound tho

[Robert Gift]

Fascinating harmonics at that low RPM setting.
I would not even recognize it as a siren unless I heard the speed up and down.
As a young child, that would be scary sounding to me.

[Jim Z]

the pitch deffitly shifted up a littel kinda of werid.

wasted brushes in the motor and/or collector rings, most likely.

[Robert Gift]

wasted brushes in the motor and/or collector rings, most likely.

I bet the collector rings because it is periodic change as though the collector brushes are passing over an oxidized or dirty area of the rings.