[kd5bjo]

Minor nitpick about the reporting:

> The team reduced the overall leaf blower noise by about two decibels, making the machine sound 37% quieter.

While a 2 dB reduction in noise does represent a 37% reduction in acoustic power, our perception of sound is logarithmic so this is extremely unlikely to "sound 37% quieter"-- Assuming the reduction is from 50 dB to 48 dB, it will sound about 4% quieter.

Much more significant is the 12 dB reduction in the "shrill and annoying" frequency range. While the 94% reduction there is probably also overstated for the same reason, the initial power level in that range will be only a portion of the overall noise output-- I wouldn't be surprised if there's a 50-75% perceived reduction of noise in this range.

[cuttysnark]

In the video, we see the students briefly rotating the model in the CAD software—with translucency on—it looks like the one main stream is divided into many spiral chambers which then exit distributed along the rim of the attachment's opposite side.

With that in mind, I wonder how much, if at all, the reduction would be if the entire nozzle were designed this way, instead of just the end bit.

[hinkley]

They probably should look at this for server cooling as well. At 2u or smaller those things are leaf blower loud, and there’s a lot of depth in those cases that could be sacrificed for decibels.

[gumby]

> Much more significant is the 12 dB reduction in the "shrill and annoying" frequency range.

Those higher frequencies travel farther than the lower frequencies, so cutting them has a bigger perceived effect (and this is all about perceived effect, I believe, not the health effects of the operator).

Just agreeing with you that acoustics is complicated and non unidimensional.

[soperj]

60db is normal conversation/background music level. I don't know why you'd assume a leaf blower would start at 50db?