Anyone who’s seen Boston Dynamics’ four-legged robots in action typically is wowed by their speed, strength, and agility, but also note how loud they are. They sound like chainsaws on steroids. And that decibel level is apparently a problem for potential customers, namely the U.S. military.

For Marines who took the robot out for a spin, that noise is apparently a deal breaker. “They took it as it was: a loud robot that’s going to give away their position,” a spokesman for the Marines’ Warfighting Lab told Military.com last week.

The Legged Squad Support Systems (LS3) robots were built by Google-owned Boston Dynamics with $32 million in funding by the Defense Advanced Research Projects Agency (DARPA) and the U.S. Marine Corps, with an assist from partners including Bell Helicopter, Carnegie Mellon, the Jet Propulsion Laboratory, and others, according to the Boston Business Journal.

To get an idea about the noise, check out this video:

Google goog bought Boston Dynamics, based in Waltham, Mass., two years ago for an undisclosed amount.

WATCH: Boston Dynamics robots in action:

The idea was for the robot to carry loads of up to 400 lbs. so it can move heavy gear and otherwise assist troops. That, however, required a fairly robust gas engine. Hence the noise.

According to Military.com, funding for this project is nearing an end.

MORE: Check out Boston Dynamics’ humanoid robot.

Boston Dynamics CEO Marc Raibert defended his company’s work. In an email to Beta Boston, he said that though the initial robot, known as “Big Dog,” was in fact noisy, subsequent iterations are considerably quieter.

But Military.com reports that the smaller, quieter robot, known as Spot, is not able to carry as much weight, and thus might be suited for other tasks, but not as a sherpa for heavy equipment.