Why are some broadband routers emitting ultrasound?

Hi Mike,

I think we'd better issue a warning:

Anyone thinking of opening up electronic devices and using things like mastic to cover components and block ventilation holes up to baffle any type of noise being generated, acoustic or ultrasonic, this may lead to overheating issues and hence be dangerous. This should not be attempted unless you are sure about what you are doing and of course, utility provided equipment like routers are the property of the utility and should not be interfered with. If you can gather enough evidence that utility equipment is causing you to hear noises that you should not be hearing, please complain to the utility and ask them to replace it. The more people who do this, the more likely action will be taken to stop such devices being issued and installed in the first place.

There are at least 2% of the population with ultrasound hearing, that's 1.4m in the UK, most of whom will have routers, electricity meters and other electronic kit that incorporate these ultrasound generating switched-mode electronics in their design, that risks these people suffering from a combination of the symptoms I listed earlier, plus other symptoms if they are also electro-sensitive. (That's if ultrasound hearing is not considered a form of ES itself. It certainly indicates a higher risk.) Most of the people affected will not understand why they have acquired their symptoms and the medical profession will not be able to diagnose them let alone provide useful treatment. Hence, awareness of this problem is needed on all sides and the use of circuitry that generates hidden ultrasound at levels that can cause awful symptoms in humans and pets, ought to be stopped.

I calculated the cost of fitting suppression in smart/digital electricity meters and compared it against the cost of the health care provided to myself during the time I had them in my home. (See:RE: Reasons why I suffered tinnitus, insomnia, chronic fatigue, and other health problems after having digital electricity meters installed) The health care costs for the minority affected is hugely more expensive compared to the cost of the suppression for all meters and there's no way I can put a cost to the utter misery caused by suffering the symptoms.

Andrew

I've wondered if some members of EngX who've read this question might have had a go at seeing whether their broadband routers also emit ultrasound. There are free apps for smartphones that let you check up to 22 kHz. I'll guess there's also a few who have even better kit that will pick up higher frequencies of ultrasound and also have meters that will detect EFs and EMFs in the ultrasonic range.

Please put the microphone 7 inches away from the router when taking measurements so that the distance is pretty much consistent to enable a fair comparison without having to worry about the inverse square law. Also, make sure it has completed its boot up sequence if turning on before measuring.

It doesn't matter if you or anyone in your household have any of the symptoms mentioned or not, but it would be interesting to know if you do find ultrasound being emitted, providing you are happy to share the information.

Please mention details of the model and type (FTTC/FTTP/POTS etc). Results showing no or very low ultrasonic emissions are as valuable as those that reveal relatively high emissions in order to find the prevalence. Happy to take results behind the scenes if you don't want to post them here yourself.

The router I tested: SR203 - FTTP.

Thanks,

Andrew

Any particular group of ultrasonic/bat detector apps that have been found to be usable?

Lots of apps have poor interfaces or are targeting the 'wrong' sorts of sounds (relative to this application)

2 or 3 'suggested' apps might be a useful start. (along with noting the recoding of the actual phone make & model, and any actual method of calibration)

Hi Philip,

I didn't want to promote one app over another, nor be told the app(s) I advise come with security flaws etc. People need to make sure they are happy to download the most suitable one they can find for their phone and their personal requirements for permissions. I believe the one I use most often is good, the waterfall chart is quite useful. It is available in the Android Store without much effort by searching for "ultrasound analyser". I don't think it has an Apple Store version, but I might be wrong. There are lots to choose from. (Try "ultrasonic sound detector" also.)

I think stating phone make and model will complicate things too much. I'm not expecting many people to take up my request (but the more the merrier) and collating by type of measuring equipment will lead to an array of results that probably wouldn't mean a lot. I understand your suggestion and it would be necessary if I was carrying out a full scientific study, but all I am looking for at the moment is: Is your router emitting an undue amount of ultrasound? Anything above 10 dB would indicate a lack of suppression. Maybe use two apps and compare. If both agree, then that's a result.

One additional thing for all who do this: Please check that any ultrasound found is coming from the router. I'm sure we are going to find other things in the home producing ultrasound. Move the phone/microphone around to check that the signal strength varies with distance away from the router only. The suggested distance of 7 inches is chosen because that is how far away I measured the ultrasound in the screenshot in the opening post. I no longer have the router, I had to return it when I cancelled the transfer of ISP, so I can't repeat the test at another distance.

Cheers,

Andrew

Last night I caught a youtube video where the vibrations of capacitors was higlighted, both as a microphone and as a speaker. It was interesting to see that they resonate at high audio frequencies and also their harmonics. These are specifically MLCC (multi layer chip capacitor) devices. The vibrations can affect the whole circuit board of course. I have not done any searching myself, but it is an interesting subject, video example here www.eevblog.com/.../

ps note the date....

The video may be April first inspired with the camera, but there is no doubt that the y5V and to a lesser extend Z7R dielectrics are very micro-phonic ==piezo electric,. Late in the last century I worked on a (very)  cheap car alarm that used the milliVolts induced in a (for the time) high value surface mount ceramic cap on a small tongue of the PCB acting as a vibration sensor. Now between you and me that design was probably one of many that led to tighter  rules on false alarm rates and over sensitivity, but the effect was there and usable. 

It would be no surprise that discharge banks click, and therefore that an electricity to sound mechanism exists, and further that some designs can set a PCB in motion, depending how thin it is an how it is supported.

regards Mike

Just for interest, this reminds me of an unsafe failure mode we had on a piece of railway signalling equipment that had us scratching our heads for a while. It was a large polycarbonate film capacitor with braided leads, sitting between the rails, and operating at a couple of kHz. The failure was that the capacitor increased in value, which is not normally considered credible. What had happened was that the capacitor had vibrated, which had caused it to act as a pump, pumping water up the braided leads to between the film "plates"! (The equivalent capacitors today have a solid block where the braid passes through the equipment housing to prevent this happening.) Taught me that capacitors definitely vibrate...

Thanks Roger,

Interesting video, possibly we all need a Crysound unit for finding kit that gives off ultrasound, but April Fool? At $899 I won't be taking a punt to find out. If it's real and lives up to its claims, it could be a very useful tool for all sorts of things, not just electrical. If not, maybe it will inspire an acoustics company to make such a thing.

Shorting out my x10 oscilloscope probe contacts and seeing if it will pick up vibrations might be a free way of veryifing the content of the video - anyone have an opinion on this before I do?

Obviously the guy who made the video is very much aware that SMPSs produce ultrasound as well as capacitors and inductors. Shame he never mentioned that some people and lots of animals can actually hear these frequencies and it drives them 'up the wall'.

Regards,

Andrew

Here's the result for my existing broadband router:

Type: SAGEMCOM CS 50001 - FTTC ADSL 2+

Basically, no difference to anywhere else in the room it's in, just background noise.