hokiefyd 

You can also get SRAM Centerline rotors (note: Centerline, not Centerlock). https://www.jensonusa.com/SRAM-Centerline-Rotor They're not solid, but their cutouts are shaped to rotate "in line" through the caliper rather than having a bunch of hole punctures in the rotor.

I, too, have experienced the "ThThThThThThTH" sound coming from my disc brakes. It seems to happen more with hydraulics than with cables for some reason. I've done a lot of swapping around on my bikes, of brake systems, pads, and rotors. Note: I have bikes with Tektro Aries (cheap cable calipers) and with inexpensive Shimano hydraulics, and both take the same brake pad, and I've swapped pads around as well as trying different configurations of brakes and rotors. I consistently get the ThThTh noise with light application of the hydraulic brakes. The exact same set of pads (like, the same physical pads) on the same physical rotors don't seem to make the same noise if squeezed by the cable calipers. I'm thinking there may be something where the steel cables in the cable brakes transmit more general noise from the brake, which drowns out the little "burble" noises you get (ThThTh) as the pads close and expose the little rotor holes. The hydraulic hoses and fluid doesn't transmit the same general noise from the brake, so you can hear that pad interface more. I don't know...just a theory.