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Phantoms (and other multirotors) louder at higher altitudes?

Discussion in 'General Discussion' started by wsalopek, Sep 6, 2016.

  1. wsalopek

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    Hi folks,

    I've been traveling between sea level and about 7000 feet...flying my P3P in both places. I don't know if it's my imagination...but...

    The P3P sounds a bit louder at 7000 feet.

    Anyone else noticed an increase in the buzzing sound of the props when flying at higher altitudes?

    Thanks...

    --

    Bill
     
  2. N017RW

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    I have not personally operated in higher elevation locations.
    IIRC the 'majority' of prop noise comes from the tips (breaking sound barrier).
    It would seem likely at high altitudes or lower air density the props need to spin faster to maintain similar flight performance compared to sea level or lower altitudes. Does this alone explain it???
    It would certainly create higher frequency sounds due to the higher RPM.
     
  3. With The Birds

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    As said.... Higher altitude = less air density (less lift) for so props will operate at higher RPM. Sound will be higher frequency. Most of the noise is generated at the tips, they arent anywhere near breaking the sound barrier on a phantom though, less than mach .4 (i couldnt get mine past 10000rpm at max stick input).
     
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  4. N017RW

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    Thanks WTB.

    I checked it out a bit closer... it would take ~28000 RPM for the Phantom's 9.4 inch prop tips to reach Mach 1.0
     
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  5. tcope

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    I've flown at 4000' up to 10,000' and all in between. I've not noticed any difference in sound. There might be a difference but it's nothing that I've noticed.