Echo Echo also has a high pitched robotic voice. To best describe it, look at his appearances from later in Alien Force from Season 2-Omniverse. 

He maybe small, but he's got a big mouth, because this silicon-based lifeform is a walking amplifier! Echo Echo can scream out sound waves that can throw back enemies at distances. Echo Echo can also duplicate himself to create over thousands of copies of himself, which gives more screams to go around! Echo Echo can also use his sound waves to create attacks like his "Wall of Sounds" or stacking his clones to create a "Sonic Tower." and more! 

Echo Echo is in a majority of episodes in Season 1.