Noise of Hub Motors

[flecc]

Hi Aldby

This posting is about NOISE you motor specifications don't mention noise output in decibels

Frank

That's because it can't be realistically quoted Frank. I've just replied on this point in an adjoining thread:

Motor noise

See also my website article on motor noise.
.

 

[Cyclezee]

Hi Aldby

This posting is about NOISE you motor specifications don't mention noise output in decibels

Frank

Hi Frank,

Point taken Frank, but I was responding to jbonds post regarding the general lack of manufacturers providing specifications in general.
I think Flecc has covered the noise issue quite comprehensively as usual.

 

[10mph]

Can dogs hear the PWM frequency?

I have a Panasonic motor driving the rear wheel through the chain. It is very quiet which I like. Just a slight noise when under max pedal force at slower speeds when accelerating. Above 10 mph the slight noise is pretty much masked by the wind in my ears. I dont have a problem warning pedestrians - I have a bell, and I slow down if someone might not know I am coming and step into my path. It is easy to accelerate again with a pedelec.

However, I have noticed at least twice, dogs barking at me and rather alarmingly pulling hard on the lead in their owner's hand. Dog's can hear up to about 60kHz, compared with 20kHz for young humans. (See Hearing range - Wikipedia, the free encyclopedia) Old humans suffer presbycusis and typically have lost 30 dB sensitivity at 10kHz by age 55.

Has anyone measured the PWM frequency for the Panasonic system on the Kalkhoff Agattu?

What about Welsh ponies? I was in the Newborough Forest on Anglesey last week and noticed some ponies start very suddenly at my bike whereas they were not at all disturbed by the runner accompanying me 20 yards ahead.

 

[brucehawsker]

I get teased every time I open my mouth. . Truth is, you guys, when you actually do the efficiency analysis of the Bafung vs time in a real world test bed you do see a drop off in efficiency. It is not that the motor fails - just it become less efficient. This is not the case if you use harder cog materials. We have been working on our bikes to maintain efficiency, and to do that we end up with the noise. Now I would stress this is a small increase, but subjectively noticable.

The reference to Panasonic and Bosch was an earlier post regarding the comparative noise of the two products.

We could go with the noisier Bafung motor - it is cheaper than our Spanish designed and built ones - but we prefer to maintain medium (2 to 3 year) high efficiency. The cost is noise....

And sorry about my spelling!

My question is - does noise matter?

 

[Scimitar]

I was going to add a comment some thing like "Let me guess, you drive a BMW" but whatever I wrote only diminished the stunning arrogance, so let's see it in all its glory.

the noise of outboard motors tells swimmers to get out of our way


Incredible.

That would be a 'whoosh' then.

 

[flecc]

I get teased every time I open my mouth. . Truth is, you guys, when you actually do the efficiency analysis of the Bafung vs time in a real world test bed you do see a drop off in efficiency. It is not that the motor fails - just it become less efficient. This is not the case if you use harder cog materials.

My question is - does noise matter?

Yes, teasing it was, but you are absolutely right about gear teeth material hardness. For a given accuracy of manufacture, a softer material will be less efficient even when new due to tooth distortion, and when aged and permanently distorted the efficiency can drop considerably before the point of failure.

The best answer for both hardness and quietness is to use helical gear teeth as the Panasonic unit does. But of course that simply isn't practical within the confines of a hub motor, provision for all the end thrusts on the epicyclic gear set being virtually impossible in the available space.

Does noise matter? Theoretically it does since it indicates a loss of energy as sound, but in practical human terms it's only the subjective impression that really counts. Some like noise as an indication of power, we as kids fixing card flaps against our bike spokes to make an engine like sound as we rode, others preferring silence.
.