This to me sounds like cell phone tower interference. Given that your neighbour also experiences it tells me that it's area based --- you could also try the experiment at say your work place (some place not geographically the same as you and your neighbour).

Find out about where the nearest cell tower is (and the nearest cell tower hub); it will probably be close. Also look for HAM radio signals or microwave radio signal towers in your area. Sometimes you can get the phone company to own up to the responsibility to sort this out and trouble shoot for you. Marc Maron (of WTF fame) had a hub on his office building that was producing this same kind of hum and it took time, but the cell phone company actually got it sorted.

DogsoverLava, post: 449385, member: 48175 wrote: This to me sounds like cell phone tower interference. Given that your neighbour also experiences it tells me that it's area based --- you could also try the experiment at say your work place (some place not geographically the same as you and your neighbour).

Find out about where the nearest cell tower is (and the nearest cell tower hub) it's will probably be close. Also look for HAM radio signals or microwave radio signal towers in your area. Sometimes you can get the phone company to own up to the responsibility to sort this out and trouble shoot for you. Marc Maron (of WTF fame) had a hub on his office building that was producing this same kind of hum and it took time, but the cell phone company actually got it sorted.

I've called the "Telecommunication & TV distribution" company and am waiting for a tech to come and measure to identify what is the source of the noise. Once I know that, I'll be able to make a move further. Till then I'm stuck in a "painful" waiting...

Are you 100% positive your guitar cables are properly shielded coaxial TS instrument cables, and not speaker cables?
Are your connectors clean, or do they have any oxidation that would hinder making good contact? (it never hurts to clean both the male cable ends, and female input jacks on the amps)
Can you, or your neighbor, the electrician, use an ohm meter and confirm that each conductor is measuring virtually zero ohms?
And be sure that the ohms measured between the tip and sleeve of your instrument cable(s) read completely 'open'?
In the interest of testing further, can you have a friend bring their guitar, amp, and cables to your house - to see if they experience the same 'whistling' using 100% of their equipment ?

Those would be the next steps I would try. I think the results would go a long way toward isolating your problem.

dvdhawk, post: 449393, member: 36047 wrote: Are you 100% positive your guitar cables are properly shielded coaxial TS instrument cables, and not speaker cables?
Are your connectors clean, or do they have any oxidation that would hinder making good contact? (it never hurts to clean both the male cable ends, and female input jacks on the amps)
Can you, or your neighbor, the electrician, use an ohm meter and confirm that each conductor is measuring virtually zero ohms?
And be sure that the ohms measured between the tip and sleeve of your instrument cable(s) read completely 'open'?
In the interest of testing further, can you have a friend bring their guitar, amp, and cables to your house - to see if they experience the same 'whistling' using 100% of their equipment ?

Those would be the next steps I would try. I think the results would go a long way toward isolating your problem.

Yes in fact I'm a kind of perfectionist and since years I make my own cables with high quality cables and plugs/jacks and I measure each soldering point with my Ohm meter. And of course I'd never use a speaker cable! And instead of bringing a friend to my place I went to friends places and there was not noise over there (I mentioned that in my initial post). This problem is recent, since few months I guess, but I only had an electric project now, after quite long time working with only acoustic recording.
Thanks for your feedback though.

BREAKING NEWS !

I discovered a unexpected way to get around the "whistling" noise problem - temporary solution but still a solution !
Someone asked me if by chance I tested with one of those single stomp boxes of the close past. Well, I've got two of them forgotten in a drawer since long time, a Boss Chorus and a Guyatone Phaser. I tested and the Phaser stops the "whistle" even in bypass! (Not the Chorus though). So that means that there IS a way to filter the godforbidden thing. For the moment I still wait for the tech person from the Telecommunication company (IBPT/BIPT) comes to detect the source and to see how it will be sorted out. After testing with a battery powered amp and still having the noise it's now sure that it is an EM interference from some source. But at least I can continue my work till then. Huffffff..........

Thank you guys all for your valuable feedback.

BD

Bad Disciple, post: 449423, member: 50501 wrote: Yes in fact I'm a kind of perfectionist and since years I make my own cables with high quality cables and plugs/jacks and I measure each soldering point with my ohm meter. And of course I'd never use a speaker cable!

You didn't go into any detail regarding the cables in your first post. It's very obvious now that you can tell the difference between cable types and can also test them with an ohm-meter. You would be surprised how few people can do either. (y)

Bad Disciple, post: 449423, member: 50501 wrote: And instead of bringing a friend to my place I went to friends places and there was not noise over there (I mentioned that in my initial post).

I did see that in your initial post. Do you see the how these are two different experiments? (Especially prior to knowing your cables are well constructed and thoroughly tested)

That's an interesting new stomp box development and work-around. I'd be curious to see if Boswell, or rmburrow might be able explain what might be going on there.

2.5kHz strikes me as an odd frequency for something to be transmitting deliberately, because it is a frequency our ears are extremely sensitive to. It would make a great human repellent if audible. I have a handheld RF Spectrum Analyzer to measure and identify background radio noise and interference, but it would "only" measure from 15MHz up into the Wifi 2.4GHz range - nothing in the audible (by humans) spectrum. I wonder if a handheld Audio RTA (or even your battery powered amp) and length of wire would help you find the source, by monitoring signal strength (or volume) - in a high stakes game of 'you're getting warmer' / 'you're getting colder'.

We've read on RO about a professional studio with noise problems that were difficult to pinpoint. It turns out a nearby neighbor was causing their problem. The neighbor's faulty equipment was polluting the studio's earth-ground, because both buildings had their electrical grounds bonded to the same underground utility pipe (which is common practice in the US). And I believe he said the solution was adding a dielectric fitting to isolate the two buildings.

Please let us know what the telecom tech finds.

Good luck, I hope the end of your frustration is in sight.

dvdhawk, post: 449432, member: 36047 wrote:
That's an interesting new stomp box development and work-around. I'd be curious to see if Boswell, or rmburrow might be able explain what might be going on there.

2.5kHz strikes me as an odd frequency for something to be transmitting deliberately, because it is a frequency our ears are extremely sensitive to. It would make a great human repellent if audible. I have a handheld RF Spectrum Analyzer to measure and identify background radio noise and interference, but it would "only" measure from 15MHz up into the Wifi 2.4GHz range - nothing in the audible (by humans) spectrum. I wonder if a handheld Audio RTA (or even your battery powered amp) and length of wire would help you find the source, by monitoring signal strength (or volume) - in a high stakes game of 'you're getting warmer' / 'you're getting colder'.

We've read on RO about a professional studio with noise problems that were difficult to pinpoint. It turns out a nearby neighbor was causing their problem. The neighbor's faulty equipment was polluting the studio's earth-ground, because both buildings had their electrical grounds bonded to the same underground utility pipe (which is common practice in the US). And I believe he said the solution was adding a dielectric fitting to isolate the two buildings.

Please let us know what the telecom tech finds.

Good luck, I hope the end of your frustration is in sight.

Thanks 'dvdhawk', yes it's a weird issue. The phaser stomp boxes (I've got two of them old ones) stop the noise and it's true that it's a really annoying "whistling" sound that remains in the ears even after turning off. I already asked few electronically 'wise' guys and they all said they have no way to measure anything under 500kHz. So, I'm afraid the tech from the Telecom company must really be very well armed, if not I'll be stuck in that mud. Of course now I just will use that temporary solution of the phaser to restart work... A ridiculous solution but true... in fact it obviously works like a filter. But the hic here is that it works on bypass which is just mysterious! Anyway, it's what exactly suits me, otherwise I couldn't work with phaser rings-and-bells on my sound.

It's a good idea that while waiting the tech guy I make a tour in the area with my battery mini-amp and headphones! That I forgot to do. Thanks for reminding it!

It's obviously a strong EM interference. By the way, there's a new challenge, just today my wife upstairs got a ridiculous noise on her laptop loudspeakers - something like a "heartbeat"!?!... And I don't have that in my place on the ground flour... And we live in a residential area. Go figure. It all starts becoming totally f**d off around, I'm telling you...

Cool vibes though,
BD

My initial thoughts is that you have an RF problem, with the RF getting demodulated in your amplifiers and presenting itself as a whine. I don't quite understand your representation of the frequency as "+/-2,5 kH". Do you mean it's a constant frequency whine or whistle pitched at about 2.5KHz, or does it wobble about a centre frequency?

The stomp boxes that you say suppresses the trouble probably have RF by-pass capacitors on the input and/or output connectors, and these would be remain in place even in Bypass mode.

Boswell, post: 449459, member: 29034 wrote: My initial thoughts is that you have an RF problem, with the RF getting demodulated in your amplifiers and presenting itself as a whine. I don't quite understand your representation of the frequency as "+/-2,5 kH". Do you mean it's a constant frequency whine or whistle pitched at about 2.5KHz, or does it wobble about a centre frequency?

The stomp boxes that you say suppresses the trouble probably have RF by-pass capacitors on the input and/or output connectors, and these would be remain in place even in Bypass mode.

Ok, it IS a whistle pitched at +/-2.5kH but it also may mean more. Here is what two other guys from homerecording.com told me after I sent them a recording of the noise:
=============================================== QUOTE:
Around 2.45kHz with two octaves (4.9 and 7.35). Not GHz, which would be a phone.
Lower than I'd expected. Not sure what would even sound in that range as Radio Frequency Interference...there was a device we used to find underground cables that ran a frequency through the line and you could pick it up with the receiver. Guy I worked with called it a "Gopher", but I can't find any reference to anything like it by googling...still. If the power company left something like that hooked up to your outside lines, it could be the source. What you heard through the headset of the "Gopher" was an audible tone about that frequency.

Summing frequencies vs octaves may mean something to someone with a better electrical background than I.
--------------------------------------------------------------
Seems to be at about 2.4 kHz and its harmonics.
It does seem to be an RF carrier of some kind the screening experiment has given me an idea.
=============================================== END OF QUOTE.
I add a graph of the noise made by one of these guys.

Today I made a tour with my battery powered mini-amp and headphones around the whole of my quarter from all sides and I detected its limits and also discovered that it was stronger when close to some newly installed power boxes along the streets in the quarter. There is NO noise outside the boundaries. I add a mapped picture that I made after that.

Attached files

Bad Disciple, post: 449438, member: 50501 wrote: Thanks 'dvdhawk', yes it's a weird issue. The phaser stomp boxes (I've got two of them old ones) stop the noise and it's true that it's a really annoying "whistling" sound that remains in the ears even after turning off. I already asked few electronically 'wise' guys and they all said they have no way to measure anything under 500kHz. So, I'm afraid the tech from the Telecom company must really be very well armed, if not I'll be stuck in that mud. Of course now I just will use that temporary solution of the phaser to restart work... A ridiculous solution but true... in fact it obviously works like a filter. But the hic here is that it works on bypass which is just mysterious! Anyway, it's what exactly suits me, otherwise I couldn't work with phaser rings-and-bells on my sound.

It's a good idea that while waiting the tech guy I make a tour in the area with my battery mini-amp and headphones! That I forgot to do. Thanks for reminding it!

It's obviously a strong EM interference. By the way, there's a new challenge, just today my wife upstairs got a ridiculous noise on her laptop loudspeakers - something like a "heartbeat"!?!... And I don't have that in my place on the ground flour... And we live in a residential area. Go figure. It all starts becoming totally f**d off around, I'm telling you...

Cool vibes though,
BD

This sounds like an EM problem to me. You need to find and borrow a good spectrum analyzer that can look at signals from 1 kHz to 1 GHz...and start looking at the low frequencies first. I'm wondering if it's one of those "big brother" smart wattmeters the power company uses, the type that sends and receives data via the AC power line. In that case, you may want to look for data signals superimposed on the incoming 220 volt service. (Be extremely careful and make sure the spectrum analyzer INPUT is ISOLATED using a step down transformer (like a 220 v to 6.3 volt filament transformer). The spectrum analyzer input may have a 50 volt max rating, so you don't want to connect the instrument directly across 220 volts; the input is unbalanced and doing this would put the case of the spectrum analyzer at 220 volts, which could kill someone on contact!) A differential input may be a workaround, but again you don't want 220 volts on the equipment input!

At any rate, once the analyzer is correctly connected, look for large peaks and record the frequencies where they are found. If you find high amplitude data in the 2.5 kHz range superimposed on the 50/60 Hz power, you may have found the source. Try running your equipment off a portable AC generator and see if the problem is still there. (Make sure ALL of your equipment is running off the generator including monitor amps, etc. Also, drive a ground rod to earth the generator; do NOT share an existing ground since it may also be "dirty". ) If the noise is gone running your equipment on a generator, then you need a suitable line conditioner between the wall and your equipment. Test the line conditioner before you buy! All you want is clean 50/60 Hz power without other garbage superimposed on it. "Dirty power" is a big problem these days with lack of maintenance to distribution lines and equipment, switching power supplies and associated transients, etc.

If this doesn't work, then search using the spectrum analyzer and look for large peaks and write down the frequencies. Do this both with the transformer isolating incoming AC, AND with a test antenna on the spectrum analyzer. EMI signals can be both conducted and radiated so both modes should be checked. If a general coverage receiver (or a field intensity meter) is available, tune in the frequencies and attempt to listen to the signal. A strong carrier peak and audible modulation in the 2.5 kHz range may identify the offending signal. Finding the source will require some legwork and a field intensity meter. If you measure the frequency accurately, you may be able to go to the regulatory authorities and ask them for the call sign and transmit antenna location. If the regulatory people ask questions, explain what is happening.

Last but not least...first check for "cockpit error"...any reference tone oscillators, etc. built in your equipment should be OFF. It would be embarrassing to spend time looking for interference and/or go to the authorities, only to have them find a test oscillator somewhere in your gear left ON. The description of the behavior of your wife's computer seems to negate this, but always good to check first.

PS: Buy any "smart" appliances lately? Like the refrigerator that notifies the manufacturer to send filter cartridges when the icemaker water filter is "spent", or a "smart" air conditioner, etc.? These appliances probably use wi fi signalling, but who knows if there is a "carrier current" modem also built in that sends data via the AC line.

One more comment: Land lines from time immortal use signalling tones in the 2.6 to 3.6 kHz range. Tones in this range may now be used for AC power line signalling. Only one way to find out; measure for it.

Good luck...

rmburrow, post: 449530, member: 46233 wrote: This sounds like an EM problem to me. You need to find and borrow a good spectrum analyzer that can look at signals from 1 kHz to 1 GHz...
Good luck...

rmburrow , thanks for your great reply, I find it really professional. In fact, I would have to make some effort to do all what you suggest, as I have no equipment like that. BUT, finally a tech from the Telecom company came with his van with antennas and stuffed with measuring devices and he got busy to do all kinds of measuring. I also made him hear the "whistle" in my amps. And we made a tour in my quarter where I already had detected, with my battery powered mini-amp and headphones, the boundaries inside which the noise is present. He said he opened a case and they will do the research to find which exactly organism is responsible. He assured me that "the problem will quite surely be resolved, even if it will take some time". I think that's the most what I cou'd have done. If ever no solution is found, I'll take a good look to your instructions. Till then, I will use that temporary solution passing through an old phaser stomp box which miraculously filters the "whistle" to my amps.

Bad Disciple, post: 449558, member: 50501 wrote: rmburrow , thanks for your great reply, I find it really professional. In fact, I would have to make some effort to do all what you suggest, as I have no equipment like that. BUT, finally a tech from the Telecom company came with his van with antennas and stuffed with measuring devices and he got busy to do all kinds of measuring. I also made him hear the "whistle" in my amps. And we made a tour in my quarter where I already had detected, with my battery powered mini-amp and headphones, the boundaries inside which the noise is present. He said he opened a case and they will do the research to find which exactly organism is responsible. He assured me that "the problem will quite surely be resolved, even if it will take some time". I think that's the most what I cou'd have done. If ever no solution is found, I'll take a good look to your instructions. Till then, I will use that temporary solution passing through an old phaser stomp box which miraculously filters the "whistle" to my amps.

OK, hopefully the telecom company tech left you a business card or other means of getting back to him. Did the tech explain specifically any of the measurements he was making, or did you note the name/model/type of instrument(s) he used? You should request a copy of his report including the measurement data. In the event the tech found something with the equipment on his van but needs to return with other instruments, that's good also. Did the tech have a isolation device connected to any test equipment which he plugged into the wall? Was a test antenna used? These "clues" are indicators a search was made for conducted/radiated measurements for EM frequencies outside the normal 50/60 Hz alternating current, superimposed on the incoming commercial power. My previous comment mentioned that "dirty power" is a big problem these days. The telecom tech either has to find the problem source and fix it, or install/recommend a power conditioner for "sensitive" equipment if the incoming commercial power is within spec. (I assume the VDE EMI specs are still applicable in the EU countries.)

You may want to try test running all your studio gear off a portable AC generator. Earth the generator (ground rod) but do not use a shared earth ground with commercial AC power because that ground may be "polluted". If your equipment works normally, you likely are facing a "dirty power" issue. Next, take some heavy wire or jumper cables and earth the generator to the power ground. If the noise returns, this will confirm the "dirty power" issue and you should tell the telecom tech that (or demonstrate if he comes back).

I make my living as a telecom consulting engineer, and interference detection/resolution is part of my work. You are finding out that recording is not all "plug and play", especially when conditions are not ideal.

rmburrow, post: 449566, member: 46233 wrote: OK, hopefully the telecom company tech left you a business card or other means of getting back to him. Did the tech explain specifically any of the measurements he was making, or did you note the name/model/type of instrument(s) he used? You should request a copy of his report including the measurement data. In the event the tech found something with the equipment on his van but needs to return with other instruments, that's good also. Did the tech have a isolation device connected to any test equipment which he plugged into the wall? Was a test antenna used? These "clues" are indicators a search was made for conducted/radiated measurements for EM frequencies outside the normal 50/60 Hz alternating current, superimposed on the incoming commercial power. My previous comment mentioned that "dirty power" is a big problem these days. The telecom tech either has to find the problem source and fix it, or install/recommend a power conditioner for "sensitive" equipment if the incoming commercial power is within spec. (I assume the VDE EMI specs are still applicable in the EU countries.)

You may want to try test running all your studio gear off a portable AC generator. Earth the generator (ground rod) but do not use a shared earth ground with commercial AC power because that ground may be "polluted". If your equipment works normally, you likely are facing a "dirty power" issue. Next, take some heavy wire or jumper cables and earth the generator to the power ground. If the noise returns, this will confirm the "dirty power" issue and you should tell the telecom tech that (or demonstrate if he comes back).

I make my living as a telecom consulting engineer, and interference detection/resolution is part of my work. You are finding out that recording is not all "plug and play", especially when conditions are not ideal.

Yes, the tech left me a business card and he said he'll send me the measurements report. So I'm happy to see that his point and your point being a professional in the same area, coincide quite well. In fact, as the problem is an EMI coming from the power towers in my quarter he concentrated on that. I had tested with a neighbor retired electrician that isolation device plugged into the wall and the noise is always present even in his house. And it's also present with that battery powered mini-amp and headphones that I tested too. And is present in the whole quarter inside a well defined boundary, not beyond it. So doesn't that mean that the "dirt" in the power is also an EM emission going through the "air"?

Thanks a lot for your advises. I'm glad to know I'm talking to a pro consulting engineer, so you wold be my best person to ask to come if you were here in Belgium. Never the less, I'll keep all your valuable info in the case if. But I can tell you that +/- one year ago, recording WAS really just "plug and play"! I got that problem recently, but as you say, nowadays many things become a lot dirtier than before, together with other things that we call progress. (I'm not complaining, because if I lived in the past, things have been even more harsh that time then...)

Bad Disciple, post: 449569, member: 50501 wrote: Yes, the tech left me a business card and he said he'll send me the measurements report. So I'm happy to see that his point and your point being a professional in the same area, coincide quite well. In fact, as the problem is an EMI coming from the power towers in my quarter he concentrated on that. I had tested with a neighbor retired electrician that isolation device plugged into the wall and the noise is always present even in his house. And it's also present with that battery powered mini-amp and headphones that I tested too. And is present in the whole quarter inside a well defined boundary, not beyond it. So doesn't that mean that the "dirt" in the power is also an EM emission going through the "air"?

Thanks a lot for your advises. I'm glad to know I'm talking to a pro consulting engineer, so you wold be my best person to ask to come if you were here in Belgium. Never the less, I'll keep all your valuable info in the case if. But I can tell you that +/- one year ago, recording WAS really just "plug and play"! I got that problem recently, but as you say, nowadays many things become a lot dirtier than before, together with other things that we call progress. (I'm not complaining, because if I lived in the past, things have been even more harsh that time then...)

EMI can be a conducted (i.e. power line) or radiated (over the air) problem, or both. Audio rectification (AR) is perhaps the most common transmitted (over the air) problem, where solid state devices rectify a strong RF signal, with varying results to the equipment. Hearing the local AM radio station on your landline telephone is a good example of AR. The tech's measurement report should provide clues concerning the source of offending signals. The electrician neighbor: Did the electrician use a "isolation transformer" and get noise, or did he use a LISN (Line ISolation Network) and still get noise? The LISN is used in EM testing to block noise on incoming AC, to power equipment undergoing EM testing. Depending on current demand, a LISN is expensive.

rmburrow, post: 449675, member: 46233 wrote: EMI can be a conducted (i.e. power line) or radiated (over the air) problem, or both. Audio rectification (AR) is perhaps the most common transmitted (over the air) problem, where solid state devices rectify a strong RF signal, with varying results to the equipment. Hearing the local AM radio station on your landline telephone is a good example of AR. The tech's measurement report should provide clues concerning the source of offending signals. The electrician neighbor: Did the electrician use a "isolation transformer" and get noise, or did he use a LISN (Line ISolation Network) and still get noise? The LISN is used in EM testing to block noise on incoming AC, to power equipment undergoing EM testing. Depending on current demand, a LISN is expensive.

Hi rmburrow, answering your remarks. Yes my electrician neighbor had at his house an "isolation transformer" and also a "stabilizer" unit (or whatever it's called). And passing through the two of them the "whistling" noise was always there. And as I pointed, I have that noise even with my battery powered mini-amp and headphones everywhere in the neighborhood.

So yes, it seems to be exactly what you suggest, an EMI conducted/radiated through the power lines in my neighborhood, and that in well defined boundaries which I could establish walking everywhere with my mini-amp & headphones. Further from these boundaries there's no such an EMI. (Here a Google picture I made).

Attached files

Hello everyone, some last news about that "whistling" EMI noise in my neighborhood (and getting it in all my amps).

Finally, I'm sad to discover that it was a misinterpretation I made with that "solution" which I thought it came using a stomp phaser box! Now that I made a bunch of meticulous tests, I found that it only slightly diminishes the "whistle", if at all... I wonder how could I have that impression the first time! I presume I may have forgotten some tone control lowered (that obviously filters it). So I'm sorry for misleading you all by saying it, but it was what I blindly thought. So no, the stomp boxes don't cancel that EMI "whistling" noise.

But I finally have a last discovery. One of my guitars has two humbuckers and they can also be combined together as two single coils from each (I presume in inversion). And it's ONLY in that case that the "whistle" is DEFINITELY cancelled ! By the way, on my two Strats (an old one and a N3 noiseless PUs) in the positions "two single coils together" the "whistle" gets considerably diminished. So the solution might have to do with the PUs combined by two and inverted I presume.

On the other hand, I'm awaiting until the Telecom company solves the problem as their tech man promised when he came to measure everything. I'll keep you updated.

BD

Bad Disciple, post: 449728, member: 50501 wrote: Hello everyone, some last news about that "whistling" EMI noise in my neighborhood (and getting it in all my amps).

Finally, I'm sad to discover that it was a misinterpretation I made with that "solution" which I thought it came using a stomp phaser box! Now that I made a bunch of meticulous tests, I found that it only slightly diminishes the "whistle", if at all... I wonder how could I have that impression the first time! I presume I may have forgotten some tone control lowered (that obviously filters it). So I'm sorry for misleading you all by saying it, but it was what I blindly thought. So no, the stomp boxes don't cancel that EMI "whistling" noise.

But I finally have a last discovery. One of my guitars has two humbuckers and they can also be combined together as two single coils from each (I presume in inversion). And it's ONLY in that case that the "whistle" is DEFINITELY cancelled ! By the way, on my two Strats (an old one and a N3 noiseless PUs) in the positions "two single coils together" the "whistle" gets considerably diminished. So the solution might have to do with the PUs combined by two and inverted I presume.

On the other hand, I'm awaiting until the Telecom company solves the problem as their tech man promised when he came to measure everything. I'll keep you updated.

BD

Sounds like you have a composite conducted/radiated EMI problem over there. When you mentioned the battery powered equipment receiving the signal, that sounds like radiated EMI to me. I assume the battery powered equipment was NOT connected to other equipment, especially equipment connected to or grounded through the electrical mains (3rd conductor ground or water pipe electrical ground). The spectrum analyzer (or a calibrated receiver) is needed to determine the frequency of the source. I have to assume the VDE limits for conducted/radiated EMI energy apply in Belgium. In some ways I recall the VDE standards are more strict than I the USA FCC Part 15 standards.

I had a case a while back, discovered when I was setting up to make a recording, of radiated/conducted EMI in a church sanctuary. I pulled off the recording OK using tube type mics and wrapping a few turns of each of the mic cables around ferrite cores, and duct taping each mess in place. I heard some "hash" in the house system when it was turned on for announcements. The conductor was annoyed about the "hash" noise...we started turning things on and off with the house system on until the culprit was found.... Turned out to be a MIDI box installed in a pipe organ. I had a FIM with me (from my regular line of work) and found excessive radiation around 2.4 MHz or so, which was also coupling into the AC; all the wiring including wiring to the organ pipes, etc. was also acting like a large antenna under the raised altar area. I did this conductor a favor and brought a spectrum analyzer along next trip through that town, and found high radiation and a EM "signature" from that MIDI box as the FIM predicted. I have to assume something was done subsequently about the MIDI box. Goes to show that EMI can turn up when least expected.

Bad Disciple, post: 449727, member: 50501 wrote: Hi rmburrow, answering your remarks. Yes my electrician neighbor had at his house an "isolation transformer" and also a "stabilizer" unit (or whatever it's called). And passing through the two of them the "whistling" noise was always there. And as I pointed, I have that noise even with my battery powered mini-amp and headphones everywhere in the neighborhood.

So yes, it seems to be exactly what you suggest, an EMI conducted/radiated through the power lines in my neighborhood, and that in well defined boundaries which I could establish walking everywhere with my mini-amp & headphones. Further from these boundaries there's no such an EMI. (Here a Google picture I made).

Within that boundary should be the source of the EMI. A field intensity meter and/or a spectrum analyzer is needed to find it. OK on the electrician trying an isolation transformer. Was the 3rd conductor ground temporarily lifted for that test? Did the electrician try a power conditioner? Was the 3rd conductor connected, or temporarily lifted for that test? Was a UPS (uninterrupted power supply) tried; was the test made with the 3rd conductor ground conducted and temporarily lifted? These tests may provide clues. Ask the electrician if the incoming 220 volt source is the secondary of the line transformer, with one side grounded. Or is the 220 volt power source the floating secondary of the power transformer, with the 3rd conductor for earthing?

Good morning Bad Disciple: Concerning your battery powered amplifier and headphones: Do you feel comfortable enough opening the plug to your headphones, and connecting 0.01 uF to 0.1 uF 100 volt capacitors between the "hot" left and right conductors (plug tip and ring) to the common ground (plug sleeve), and listening for the interference while the capacitors are connected? In the event the "whistle" goes away with the capacitors connected, you will have successfully "bypassed" offending RF to ground. Small ceramic or mylar capacitors should be available which should fit inside the plug housing. Insulate the leads to prevent shorts.

Ive been having exact same problem with my equipment. Honestly,it could be a change in hearing. After all my investigating I found that Many on youtube describe it as ONCE YOU HEAR IT, YOU CANT UNHEAR IT phenomenon.Its always been there perhaps is the fact. Something just triggered a brain response to certain frequencies. Seems it will now never go away. Watch some videos on eq sweeping distorted guitars. They all point to these things. Just all eq sweeping removing these frequencies.

Well - the numerous scope traces suggest it's not his hearing, and of course, it was back in 2017 he posted it. What is remarkable is that he never let us hear it. Scope traces and frequency plots are fixed points in time - cell phone interferences is instantly noticeable. He called it a whistle, then a whine - people cannot describe sound accurately at all, so a recording would have been a great starting point.