There are three general types of chippers available in the market...

* High-Torque Roller which is the biggest shredders and usually used in for shredding residential areas... Though it's big in nature it produces low sounds...

* Drum - it is also electric powered , but produces louder sounds than high torque roller. The wood chips produced are a bit larger, good thing it is corrected by modern technology...

*Disk - steel disk with knives attached to it and act as the chipping mechanism... it's the smallest in size but proves to be more powerful as well... It produces a more consistent wood chips and chops..

There are other designs, sizes, and styles available in the market.. I hope this one at least helps.. :)