Silencer for leaf blowers picked up by Black & Decker

Original source (on modern site)

There are few power tools that raise a neighbor's hackles quite like the leaf blower. Sure, others can be loud, but there's just something about their particular ear-splitting drone that cuts in like a dentist's drill. Perhaps it's people's frustrating tendency to use them early in the morning, when folk are trying to sleep in. Perhaps it's the knowledge that using a broom or rake would not only be quieter, but also wouldn't just move all the leaves onto your lawn. Either way, it's the kind of problem engineering students love to tackle.

The team's design ended up taking the form of an attachment that fits over the end and dampens the specific frequencies blasted out by leaf blowers, without reducing the force of the air. They compare it to a silencer for a gun, or a muffler for a car. The researchers started by analyzing the sounds leaf blowers made, and how they make them.

"The sound that comes out of this leaf blower is very complicated and it contains a lot of different frequencies," said Andrew Palacio, a member of the research team. "A lot of different notes on a piano would be a good analogy."

It turns out, among the cacophony that these tools emit are some high frequency noises that are particularly annoying to the human brain. The team designed their attachment to specifically dampen these frequencies, reducing them by around 12 decibels (dB) at 50 ft (15 m), or 94% quieter. The overall noise has come down by about 37% - that means there'll still be some noise of course, but this device should take the edge off it.

"It's the difference between hearing a high-pitched whistle and hearing what you might think of as wind noise," said team member Madison Morrison.

It's not be as dramatic a reduction as other recent leaf blower advances, like that from Whisper Aero last year, which cut overall noise by more than half. But that was mostly a tech demo for the company's super-quiet electric jet engines for aircraft. The new design from the Johns Hopkins team is poised to become a commercial product within the next two years or so.

"It's not just some cool theoretical thing that will sit on a shelf and never be heard from again—this is ready to be mass manufactured," said Nate Greene, senior product manager at Stanley Black & Decker, who have picked up the pending patent. "This is a really rare and dramatic level of success."

The team says the design could also be adapted to make quieter versions of other appliances like vacuum cleaners and hair dryers.

Check out the leaf blower silencer in action in the video below.