Sonorosian

Sonorosians are creatures made of living sound waves encased in containment suits from the planet Sonorosia.

Appearance
Because they are made of living sound waves, a Sonorosian's appearance is actually small, white and green containment suits made of silicon.

According to Matt Wayne, the green circle-shaped indents on the back of a Sonorosian's hands are sound holes that help them resonate.

Powers and Abilities
Sonorosians can scream at audible to ultrasonic frequencies, capable of overloading machinery and stopping projectiles in mid-flight.

Sonorosians can duplicate themselves, similar to Splixsons, but different in that the clones are not linked with each other in any way, allowing entire groups to be knocked out without harming the rest. They also seem to be able to ably their duplication powers on whatever objects they are holding. However, this was retconned by Derrick J. Wyatt as a foreign ability given to Echo Echo because of a glitch with the original Ultimatrix.

Using this sonic screams, Sonorosians can detect vibrations in the ground, use echolocation, and create forcefields.

Sonorosians can channel vibrations to enhance their screams. They can also can transmit their sound waves through speakers, such as phones.

Sonorosians are quite strong and agile for their size.

Sonorosians seem to be capable of levitation. However, this was also retconned by Wyatt as a foreign ability given to Echo Echo because of a glitch with the original Ultimatrix.

Weaknesses
Because their appearance is a containment suit, a Sonorison's body is rather fragile. That means they can easily be destroyed in battle, such as by an Aerophibian's neuroshock blasts.

Omnitrix Transformation
The Omnitrix's Sonorosian representative is named Echo Echo, who first appeared in the Alien Force episode "Ben 10 Returns: Part 2". Echo Echo has appeared in almost every subsequent series except the reboot.

The Ben Tennyson of Dimension 23 has an equivalent of Echo Echo named Copy Copy, who was confirmed to exist in the Omniverse episode "And Then There Was Ben".

Echo Echo has also been used by Albedo. Echo Echo is available in Mad Ben's Omnitrix, as glimpsed in the Omniverse episode "It's a Mad, Mad, Mad Ben World: Part 2".

Etymology
"Sonorosian" is a play on sonic and sonar.