Okay, here goes. I tested 4 types of props. OEM, Maytech, Autel Xstars and the tri-blade folding carbon fibers. Sound readings were taken with the H motors running (duh), but NOT in flight. I took two readings, one with the sound meter in the center of all the props at prop level, and another from right in front of the RealSense. Temperatures given are the range found on each motor within 30 sec of landing, using a laser thermometer. Note that all flight times are from 16.6v to 14.4v, and in similar wind. No manuevering other than take-off, minor adjustments to compensate for GPS drift (wasn't using RS), and landing. No landing skid retract. Just minimal hover, about 2-5' off the ground. All in similar breeze of 5-10 (checked with hand anemometer), and similar temp (75-78 deg). Same battery was used each flight, so you know there was some time between.
Times may seem rather short. Keep in mind I had prop guards in place, since I wasn't going to be far from the ground, and I stopped at 14.4v, not at a warning.
OEM: 80.2/76.4dba - 58-67F - 7:40
MT: 80.6/77dba - 67-74F - 8:08
Autel: 77.8/73.6dba - 57-62F - 8:32
TB: 74.1/66.3dba - 70-80F - 9:10
Something I think is worth mentioning: If you use DJI-style props, they need to be
very snug. The H motors
STOP when they stop, and 2 of my Autels went for independent flight. Keeping that in mind, I tightened the tri-blades down further and FIVE of them took off when the motors stopped. That may be because they were stopped mid-air rather than on the ground though, so they went from flight power, not idle (odd, it wouldn't land, so I killed the motors and let it drop the last 6-8 inches to the grass - in hindsight, RealSense may have been accidentally on and I didn't notice it).
Ralphy, you might want to make the ones with vertical offset more offset. No bumping at idle, but heard it in flight. Most people likely wouldn't hear it as the H would be too far away, but I had it hovering within about 10' of me throughout the hover testing, so I heard it as it compensated for wind (both with the Autels and the tri-blades).
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