On 2018-12-27, Jeff Liebermann <jeffl@cruzio.com> wrote:
> On Wed, 26 Dec 2018 21:43:53 +0200, Tauno Voipio
><tauno.voipio@notused.fi.invalid> wrote:
>
>>On 26.12.18 20:45, Jeff Liebermann wrote:
>>> On Wed, 26 Dec 2018 11:01:56 -0500, bitrex <user@example.net> wrote:
>>>
>>>> Here's some interesting papers on sources of noise from small DC motors:
>>>> <https://www.mdpi.com/2072-666X/9/2/84/pdf>
>>>> <http://downloads.hindawi.com/journals/ijrm/2006/063214.pdf>
>>>> The first seems to indicate a significant source of noise at high freq
>>>> in small motors is excited resonance of the motor housing itself
>>>
>>> Suggestion: Remove the propellers from the quadcopter and run the
>>> motors without the props. The residual noise should be 100% chopper
>>> noise. I did that in the past on my Walkera XR-350 clone:
>>> <http://www.learnbydestroying.com/jeffl/pics/drivel/slides/Walkera%20QR%20X350%20Drone.html>
>>> and heard very little remaining noise from the motors. However, my
>>> hearing is not the best, and I didn't bother making any measurements
>>> with an SPL meter. If I find time, I might try it again later today.
>
>>If you remove the propellers, you should substitute a
>>comparable amount of torque load to keep the operating
>>conditions. The noise will be significantly lower when
>>there is no torque load.
>
> I could do that using a disk (washer) with a radius of about 30% of
> the propeller radius (center of mass) and having the same weight as
> the four propellers. I think I have some spare props left over from
> my last attempt at indoor flying (before I added the shrouds). It's
> not a good equivalent load torque because it's not pushing air, but
> methinks the inertial load of the disk (washer) will be sufficient to
> have the chopper produce some vibrations.
Props effectively have negative weight in flight. if you're looking for
bearing noise. I guess you can run it upside down with the weights
summing to the craft's normal weight
--
When I tried casting out nines I made a hash of it.
Reply by Jasen Betts●December 28, 20182018-12-28
On 2018-12-26, Tauno Voipio <tauno.voipio@notused.fi.invalid> wrote:
> On 26.12.18 20:45, Jeff Liebermann wrote:
>> On Wed, 26 Dec 2018 11:01:56 -0500, bitrex <user@example.net> wrote:
>>
>>> Here's some interesting papers on sources of noise from small DC motors:
>>> <https://www.mdpi.com/2072-666X/9/2/84/pdf>
>>> <http://downloads.hindawi.com/journals/ijrm/2006/063214.pdf>
>>> The first seems to indicate a significant source of noise at high freq
>>> in small motors is excited resonance of the motor housing itself
>>
>> Suggestion: Remove the propellers from the quadcopter and run the
>> motors without the props. The residual noise should be 100% chopper
>> noise. I did that in the past on my Walkera XR-350 clone:
>> <http://www.learnbydestroying.com/jeffl/pics/drivel/slides/Walkera%20QR%20X350%20Drone.html>
>> and heard very little remaining noise from the motors. However, my
>> hearing is not the best, and I didn't bother making any measurements
>> with an SPL meter. If I find time, I might try it again later today.
>
>
> If you remove the propellers, you should substitute a
> comparable amount of torque load to keep the operating
> conditions. The noise will be significantly lower when
> there is no torque load.
yes, EG. fit an aluminium flywheel with a magnetic brake, or some
other near-silent mechanical load
--
When I tried casting out nines I made a hash of it.
Reply by Jeff Liebermann●December 28, 20182018-12-28
On Wed, 26 Dec 2018 22:26:18 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
>On 12/26/18 7:51 PM, Jeff Liebermann wrote:
>> However, I won't have time for a few days. The doctors will be
>> removing two large kidney stones tomorrow and I may need some time to
>> recover. To be continued when possible.
>Yikes. Best wishes for a speedy recovery--I'll pray for you.
>Cheers
>Phil Hobbs
Thank you. I could use all the help I can get. I survived. Left
stone is gone. Right stone is split into tiny rubble, and should pass
when the urologist removes the stents in a week. It's now 4AM on the
left coast and I can't sleep due to pain and having constantly run to
the bathroom. That should diminish sometime tomorrow. I'll
eventually be back to normal, except for my contribution to the
doctor, hospital, anesthesiologist, etc bills.
My apologies for the off topic topic, but it's literally all I can
think of at this time.
--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
Reply by Klaus Kragelund●December 27, 20182018-12-27
If the switching frequency is 8kHz, there is of course also harmonics and subharmonics, so just removing the 8kHz from the recording is not a representative figure
Cheers
Klaus
Reply by Jeff Liebermann●December 27, 20182018-12-27
On Thu, 27 Dec 2018 02:28:58 -0000 (UTC), John Doe
<always.look@message.header> wrote:
>Jeff Liebermann <jeffl@cruzio.com> wrote:
>> Removing the 300 and 8000Hz tones would probably not have much of
>> an effect on the overall noise level
>Maybe because you can't hear it. It makes a big difference to me.
>Shown by pulling my 8 kHz equalizer slider down to zero.
It's possible that I can't hear 8KHz. I haven't tested my hearing in
the last 5 years or so.
>You say "I never guess".
Close. I said: "I never guess when I can also test".
In other words, if there's a way to test my assertions, I prefer doing
that instead of guessing. If that fails, use "the force".
Actually, I do quite a bit of guessing, far more than I consider
acceptable. My favorite excuse is lack of time, which I shall now
invoke as my reason for not testing my hearing or manipulating the
audio track. Besides, it's your problem, not mine, so you should be
doing the experimentation.
>You might want to start.
>Even Blinkin was guessing, and he could at least hear...
>https://youtu.be/zJQ7FxLzhVs
Take the recording from the YouTube video and notch out the 8KHz.
Audacity should be suitable for the task:
<https://manual.audacityteam.org/man/notch_filter.html>
Does it now sound acceptable? If so, build a hearing aid or
mechanical headset with a built in 8KHz notch filter, which should
help you fly without irritating noises. Hmmm... I smell a product
idea.
--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
Reply by Phil Hobbs●December 26, 20182018-12-26
On 12/26/18 7:51 PM, Jeff Liebermann wrote:
> On Wed, 26 Dec 2018 21:43:53 +0200, Tauno Voipio
> <tauno.voipio@notused.fi.invalid> wrote:
>
>> On 26.12.18 20:45, Jeff Liebermann wrote:
>>> On Wed, 26 Dec 2018 11:01:56 -0500, bitrex <user@example.net> wrote:
>>>
>>>> Here's some interesting papers on sources of noise from small DC motors:
>>>> <https://www.mdpi.com/2072-666X/9/2/84/pdf>
>>>> <http://downloads.hindawi.com/journals/ijrm/2006/063214.pdf>
>>>> The first seems to indicate a significant source of noise at high freq
>>>> in small motors is excited resonance of the motor housing itself
>>>
>>> Suggestion: Remove the propellers from the quadcopter and run the
>>> motors without the props. The residual noise should be 100% chopper
>>> noise. I did that in the past on my Walkera XR-350 clone:
>>> <http://www.learnbydestroying.com/jeffl/pics/drivel/slides/Walkera%20QR%20X350%20Drone.html>
>>> and heard very little remaining noise from the motors. However, my
>>> hearing is not the best, and I didn't bother making any measurements
>>> with an SPL meter. If I find time, I might try it again later today.
>
>> If you remove the propellers, you should substitute a
>> comparable amount of torque load to keep the operating
>> conditions. The noise will be significantly lower when
>> there is no torque load.
>
> I could do that using a disk (washer) with a radius of about 30% of
> the propeller radius (center of mass) and having the same weight as
> the four propellers. I think I have some spare props left over from
> my last attempt at indoor flying (before I added the shrouds). It's
> not a good equivalent load torque because it's not pushing air, but
> methinks the inertial load of the disk (washer) will be sufficient to
> have the chopper produce some vibrations.
>
> However, I won't have time for a few days. The doctors will be
> removing two large kidney stones tomorrow and I may need some time to
> recover. To be continued when possible.
>
>
>
Yikes. Best wishes for a speedy recovery--I'll pray for you.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510
http://electrooptical.nethttp://hobbs-eo.com
Reply by John Doe●December 26, 20182018-12-26
Jeff Liebermann <jeffl@cruzio.com> wrote:
> John Doe <always.look@message.header> wrote:
>> bitrex <user@example.net> wrote:
>>> Klaus Kragelund wrote:
>>
>>>> It sounds to me like it is switching noise from the motor
>>>> drive, which causes movement of the motor windings
>>>>
>>>> It sounds to be a steady noise frequency which it won’t be if
>>>> it is related to the blades
>>>>
>>>> No way to change it, except to change the motor control SW or
>>>> filter the output to the motor to reduce the switching current
>>>> ripple
>>
>>> I hear it now. Had to put on headphones, on laptop speakers I
>>> only hear the lower pitched blade noise
>
>> I was just coming back to post about that possibility. The
>> frequency is at least 8 kHz. A bad sound system or failing ears
>> might not even know what sound we're talking about.
>
> <https://www.youtube.com/watch?v=FSwZQtqWyHw>
> Removing the 300 and 8000Hz tones would probably not have much of
> an effect on the overall noise level
Maybe because you can't hear it. It makes a big difference to me.
Shown by pulling my 8 kHz equalizer slider down to zero.
You say "I never guess". You might want to start.
Even Blinkin was guessing, and he could at least hear...
https://youtu.be/zJQ7FxLzhVs
Reply by Jeff Liebermann●December 26, 20182018-12-26
On Wed, 26 Dec 2018 07:51:31 -0000 (UTC), John Doe
<always.look@message.header> wrote:
>bitrex <user@example.net> wrote:
>
>> Klaus Kragelund wrote:
>
>>> It sounds to me like it is switching noise from the motor drive,
>>> which causes movement of the motor windings
>>>
>>> It sounds to be a steady noise frequency which it won’t be if
>>> it is related to the blades
>>>
>>> No way to change it, except to change the motor control SW or
>>> filter the output to the motor to reduce the switching current
>>> ripple
>
>> I hear it now. Had to put on headphones, on laptop speakers I only
>> hear the lower pitched blade noise
>I was just coming back to post about that possibility. The frequency
>is at least 8 kHz. A bad sound system or failing ears might not even
>know what sound we're talking about.
Reply by Jeff Liebermann●December 26, 20182018-12-26
On Wed, 26 Dec 2018 21:43:53 +0200, Tauno Voipio
<tauno.voipio@notused.fi.invalid> wrote:
>On 26.12.18 20:45, Jeff Liebermann wrote:
>> On Wed, 26 Dec 2018 11:01:56 -0500, bitrex <user@example.net> wrote:
>>
>>> Here's some interesting papers on sources of noise from small DC motors:
>>> <https://www.mdpi.com/2072-666X/9/2/84/pdf>
>>> <http://downloads.hindawi.com/journals/ijrm/2006/063214.pdf>
>>> The first seems to indicate a significant source of noise at high freq
>>> in small motors is excited resonance of the motor housing itself
>>
>> Suggestion: Remove the propellers from the quadcopter and run the
>> motors without the props. The residual noise should be 100% chopper
>> noise. I did that in the past on my Walkera XR-350 clone:
>> <http://www.learnbydestroying.com/jeffl/pics/drivel/slides/Walkera%20QR%20X350%20Drone.html>
>> and heard very little remaining noise from the motors. However, my
>> hearing is not the best, and I didn't bother making any measurements
>> with an SPL meter. If I find time, I might try it again later today.
>If you remove the propellers, you should substitute a
>comparable amount of torque load to keep the operating
>conditions. The noise will be significantly lower when
>there is no torque load.
I could do that using a disk (washer) with a radius of about 30% of
the propeller radius (center of mass) and having the same weight as
the four propellers. I think I have some spare props left over from
my last attempt at indoor flying (before I added the shrouds). It's
not a good equivalent load torque because it's not pushing air, but
methinks the inertial load of the disk (washer) will be sufficient to
have the chopper produce some vibrations.
However, I won't have time for a few days. The doctors will be
removing two large kidney stones tomorrow and I may need some time to
recover. To be continued when possible.
--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
Reply by John Doe●December 26, 20182018-12-26
tabbypurr@gmail.com wrote:
> bitrex wrote:
>> Klaus Kragelund wrote:
>>> It sounds to me like it is switching noise from the motor drive,
>>> which causes movement of the motor windings
>>>
>>> It sounds to be a steady noise frequency which it won't be if
>>> it is related to the blades. No way to change it, except to
>>> change the motor control SW or filter the output to the motor to
>>> reduce the switching current ripple
>> if it's electrically excited/resonant acoustic noise caused by a
>> specific PWM harmonic in the audible range (the whine seems to be
>> consistent in frequency across the motor power output range) what
>> about a parallel-series LC band-reject in the PWM drive output to
>> the motors?
>
>> The armature can't resonate at that frequency if it can't get any
>> power from the controller at that frequency
>
> The whining noise is clearly constant frequency as the motors pick
> up speed, and can't possibly be produced by the propellors. There
> are 2 solutions:
> 1. move to an ultrasonic switching frequency
> 2. Infiltrate varnish etc into the switched mode inductor & put foam
> under the PCB it's on.