Is it a uniform humm, or does it change pitch?

I am using one inline being fed directly by a supra pump in tank.

It does not have a constant uniform humm, It constantly changes pitch.is this the normal sound?

 

Mine sounds a little crazy on first key-on, but I think it has more to do with the check-valve in my intank pump being fuckered, it eventually gets a steady, LOUD drone, and vibrates through the whole chassis (hard-mounted). Post a video of it, if I need to I'll do the same