The mystery behind a "strange noise" that a NASA astronaut heard coming from the Boeing Starliner spacecraft while aboard the International Space Station has been solved, the space agency said Monday.

Astronaut Butch Wilmore first reported the pulsating sound coming from a speaker inside the spacecraft to Mission Control at Johnson Space Center in Houston on Saturday, just days before it was set to leave the station and return to Earth on autopilot.

NASA said in a statement on social media that the pulsing sound from the speaker has since stopped and determined the feedback was the result of an audio configuration between the space station and Starliner.

"The space station audio system is complex, allowing multiple spacecraft and modules to be interconnected, and it is common to experience noise and feedback," NASA said. "The crew is asked to contact mission control when they hear sounds originating in the comm system. The speaker feedback Wilmore reported has no technical impact to the crew, Starliner, or station operations, including Starliner’s uncrewed undocking from the station no earlier than Friday, Sept. 6."

NASA ASTRONAUT STUCK IN SPACE REPORTS ‘STRANGE NOISES’ FROM TROUBLED STARLINER CAPSULE

Butch Wilmore and Suni Williams

NASA’s Boeing Crew Flight Test astronauts Butch Wilmore and Suni Williams pose on June 13 from inside the vestibule between the forward port on the International Space Station’s Harmony module and Boeing’s Starliner spacecraft. The astronauts have been stuck in space since June. (NASA)

The mystery of the pulsating sound comes as Starliner is slated to undock from the space station empty and attempt to return on autopilot with a touchdown in the New Mexico desert. 

Boeing-Astronaut Launch

Boeing's Starliner spacecraft is docked to the Harmony module of the International Space Station on July 3 as seen from a window on the SpaceX Dragon Endeavour spacecraft docked to an adjacent port. (NASA via AP)

Wilmore and astronaut Suni Williams, who have been stuck on the space station since June, are expected to remain in space until February after NASA decided it was too risky to bring the seasoned pilots back to Earth aboard Starliner. The current plan is to bring the astronauts back in a SpaceX capsule.

NASA PLANS TO SEND 2 ASTRONAUTS INSTEAD OF 3 TO ISS SO PAIR STRANDED BY TROUBLED BOEING STARLINER CAN RETURN

The astronauts were originally slated for a weeklong trip, but the mission has been mired in problems after thruster failures and helium leaks.

The balloon-shaped Starliner spacecraft is docked to the Harmony module of the International Space Station high above Egypt's Mediterranean coast.

NASA said the mysterious pulsating noise was the result of an audio configuration between Starliner and the International Space Station. (NASA via AP, File)

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Boeing had counted on Starliner’s first crew trip to revive the troubled spacecraft program after years of delays and ballooning costs. The company had insisted Starliner was safe based on recent thruster tests in both space and on the ground.

Fox News Digital’s Bradford Betz and The Associated Press contributed to this report.