Ultrasonic commutator and tinnitus

[RIchardF]

from Anatomy of a Silent Fan

Commutator Switching Frequency Noise is described by JMC...

"The stator motion is a square wave that is switched on and off before and after the peak torque position. This motion causes a small amount of undulation in motor torque, producing an audible noise caused by the lower frequency commutation operation. Each small torque causes a minute contracting of the entire fan structure and results in an audible clicking noise while the fan is operating."

This noise is most often heard as a rapid clicking or buzzing. JMC's solution to commutator switching noise is to put the frequency up to 25KHz, where it is inaudible to human beings. This is the main feature of their PWM fans.

I am wondering if my tinnitus is being aggravated by this practice. I can't use the computer I built because it aggravates it, even with the the double ball bearing radiators fans set to medium speed, the GPU fans kept at a fairly low level, and the machine being across the room in a mostly closed closet. The overall volume from the computer that I can hear is low but it is the only thing, besides listening to music via headphones, that really aggravates my tinnitus — and it aggravates it more. I wonder if ultrasonic frequencies are acting in combination with high frequencies that I can't hear because of my age, coming from the ball bearing fans on the radiator and the ball bearing fans on the GPU. It seems clear enough that just because the brain may not hear sound that doesn't mean it can't cause damage.

My Macbook Pro doesn't bother me at all as long as I don't do anything that causes the fan to speed up a lot. Fan noise in general aggravates my tinnitus but it seems like the low level of noise I'm hearing from the newly build computer has to be about more than just overall decibels.

The effect of airborne ultrasound on hearing has not been thoroughly studied, but young normally hearing adults seem at greater risk for very-high-frequency hearing loss. The Occupational Safety and Health Administration (OSHA) has adopted ultrasonic hearing protection working standards. Ultrasonic cleaners and related technology (ultrasonic welders, etc.) are an industrial source of high audio and ultrasound of sufficient energy to induce hearing loss.

In addition, the presence of both high audio frequencies and ultrasound in the workplace can increase the ear damage risk...

http://www.tinnitus.vcu.edu/Pages/Ultra ... earing.pdf

[edh]

Try stopping the fan even briefly and see if it makes a difference?

[RIchardF]

The radiator has three fans and the GPU has two. All are ball bearing models.

I don't know if any of the sleeve type fans in the system have ultrasonic commutators.

The trouble with my tinnitus is that when it gets aggravated the sound lasts for weeks. So even if I turn off a fan or all of them the noise will still be there. It lessens each day some if I don't further aggravate it. The worst tonal tinnitus noise did drop off fairly quickly after I stopped using the computer completely.

All I know is that when I use the computer it gets bad — much worse than from anything else, even my noisy fridge or a car trip with the window partially down at 60 MPH. This is what makes me thing it's not just the decibels that are the problem but the frequencies.

I think the ball bearing fans on the radiator are the main source of the issue but it could also be the GPU as well as the other fans.