It’s kind of an “open-secret” in the auto and tech industries that Apple is developing an electric vehicle codenamed “Project Titan”, yet for the most part, the Cupertino-based company has been able to keep details under wraps.

In helping keep any development secret, Apple is believed to be using a shell company called Sixty Eight Research based in Sunnyvale, California. Neighbors have recently been reporting heavy security presence and a lot of noise around the location. 

A local news crew reported on the disturbance earlier this week, and since then the security has reportedly relaxed around the facility.

But neighbors told KPIX 5 that the level of security was becoming disturbing:

“At three in the morning, they have deliveries. It’s very dark, very secretive. We don’t know what’s going on, but almost every night there is noise that wakes the dogs up,” Joann Porter said.

Neighbors on Bartlett Avenue near the facility said security guards tail them when they walk their dogs. “You have security guards following you in their cars,” Porter said.

Porter added that she was hearing the sound of metal sheets slamming and clanking all day, but also a sound described as a ‘high-pitched hum”, which sometimes could be heard all day.

The news crew didn’t catch the sound while filming but Jim Porter imitated it on camera, see the video below, and it could fit the description of the sound an electric motor makes when being pushed to its limits.

In 2014, the Sunnyvale City Manager said that Apple was granted a building permit for “an auto testing facility.”

Here’s the news report from KPIX 5:

Earlier this year, it was revealed that Apple has registered three car-related domain names that hint at its electric car project, while last month, the Apple veteran employee who has been overseeing the program reportedly left the company.