Drones have become a potent military threat, particularly on the small scale. Nimble multi-rotor drones are fast, difficult to spot, and can cause plenty of harm if allowed to go about their work unhindered. The first step to dealing with this issue is detection—a problem that [Agam Rossen] has put some work into.

The result is VolAnti—an open-source drone detector. This route was chosen as a reliable way to detect incoming multi-rotors, since spinning propellers tend to create a telltale sound that can be plucked from the noise quite specifically. In a world where fiber optic drones eschew RF emissions, it also proves particularly useful for early warning of such craft.

VolAnti relies on a small four-microphone array, with the I2S output of all four mics summed together. The output is then fed into a 2048-point FFT running every 32 ms on an ESP32-S3. A comb score is given to try and pick out different blade rates from 70 Hz to 2000 Hz. Multiple detection algorithms run in parallel, because [Agam] noted a problem—using an adaptive noise floor would miss drones that arrived in the area and hovered in place. With the noise not varying, it would get filtered out by the adaptive floor, so one algorithm in the four runs with no floor to catch drones that aren’t moving. Files are on GitHub for those curious to learn more.

We’ve featured other acoustic detection projects before, too. If you’re working on something similar, or conversely, you have the inside scoop on how to hide a drone’s noise signature, don’t hesitate to let us know on the tipsline.

Most high-tech police drones are deployed for high-speed chases or search and rescue missions, but officers in Kirkland, Wash., recently launched one indoors for a wilder reason: tracking a live bobcat sitting at the top of a resident’s staircase.

According to a Kirkland Police Department Facebook post, the incident unfolded in the Moss Bay neighborhood last week after a resident heard loud banging inside their home and called 911 to report a break-in.

Responding officers expecting a human burglar were surprised to find the intruder was a bobcat.

In order to maintain a safe distance and manage the response, officers deployed an unmanned aircraft to monitor the cat’s movements inside the home.

The bobcat was corralled into an isolated room until the Washington Department of Fish and Wildlife arrived, according to the Facebook post. The bobcat was sedated and later released near Forbes Creek, close to the natural habitat where it was found.

The bobcat is believed to have climbed a tree and jumped through an open window to gain entry possibly drawn inside by the resident’s cat, which was later found unharmed.

The indoor operation highlights how Kirkland has expanded its use of aerial technology since launching a public safety drone program in 2022. Managed centrally across the city’s Police, Fire, and Public Works departments, the program maintains five aircraft and 17 FAA-licensed pilots specifically trained for tactical searches, search-and-rescue missions, and scene documentation.

Police recommend that if a bobcat enters your home, move people and pets away from the area and call 911.

Amazon plans to expand Prime Air drone delivery to nearly 500 cities by 2026, a sixfold jump, despite mounting safety incidents and federal scrutiny.

The FCC is considering restrictions that could prevent some previously approved DJI drones from being sold in the US. Existing owners would not be affected.