I have a rather annoying noise at 5333Hz any ideas what is causing it?

Here it is in a rather nasty iPhone recording at the tweeter the cursor was bit off in the grab below…its actually 5.333KHz. Happens day and night every minute or so.

and here is a link to the noise in wav format (6 seconds only)

any ideas? Best I can find is lift motor controllers (Seimens) might use this frequency and while I do have lifts in my building I’m not near the motor room.

Heart rate monitor used with exercise machines?

Sadly nothing like that around me and the walls all concrete and rebar. Now I am trying to find out if it’s before or after the active crossovers feeding the amps, all 8 channels for 2 speakers

What steps have you taken to determine the source?
Have you tried a mains filter to determine if it comes from the mains?
It it also there when you have only the amplifier connected to the speakers without any source equipment?
Have you tried disconecting the mains earth per device to determine if it is a groundloop? (No you are not going to instantly die by disconnecting mains earth)

There are many devices on the net nowadays that communicate with each other via tones, like fire alarms, energy meters, control systems etc etc.

But offcoarse the most propable cause is the governement or aliens trying to reprogram your brain via the mains supply.

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Bugger - we’ve been twigged…

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I am an electrical guy so I know my way around mains wiring and have a license in my home country to do appliance repairs and I’ve been repairing HIFI gear for 45+ years…I’m trying to see if anyone has ideas on the source of the noise which is a pretty specific 5333Hz

No Ethernet over mains, power is on mains filters (240VAC) and I’ve tried turning off all breakers bar the dedicated HIFI feed, no Wifi, no cordless, no mobiles, or anything else powered in the house Bar the HIFI and still the noise is there and it’s on different setups in other rooms too, different amps cables and Pre/pro and speaker setups.

I’m going to try a balanced mains isolation setup that I have just completed building. Next step if that doesn’t help is A regenerator like PS Audio P3 but that’s an expensive buy.

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Maybe a stupid question but is only there while music is playing or is it also audible when the play is paused (nothing playing at all)? If it’s audible when nothing is playing, you can further investigate by disconnecting source connections.

Can really only hear it when the music is not playing…but the funny thing is I can’t hear it at the speaker but my wife can hear it across the room. I can hear it on the recording I linked tho. As the recording is done in a normal room right at the tweeter and there is other background noise like aircon etc in the room it’s harder to hear but the spectrogram reveals it well

Can certainly imagine that this is annoying…

Just to be sure : Is this tone really emitted by the tweeter ? Can your wife still hear it, with the entire audio system turned OFF ?
Doesn’t seem to make sense that it isn’t audible at the source, yet very aubible at another location. Especially at a frequency, where any normal tweeter would start to get directional…
Just for your info : yes, it is clearly (annoyingly) aubible on your recording. Even on a phone.

Does this mean that the airco was off, too ? If not, could it be that a motor in your airco is PWM driven ? Or a motor in another ventilation unit in your house ?

Other that that, I only have silly suggestions :). Your frequency is nicely divisible by three. Meaning : nice and round integers, when converted RPM. 320.000 RPM in this case. I understand that this is a pretty common rotational speed for dental drills. You don’t happen to have a workaholic dentist as a neighbour, do you :slight_smile: ?

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By the way - it is not a constant tone. Haven’t analyzed, just by ear I’d say : not present before 1,5 second. Present after that. At 3,5 seconds a guesstimated 8dB louder. After 5,5 seconds, gone.

It seems to be an interval. Not sure if that’s helpful (perhaps you just moved your phone)

Any television or video kit on the hifi circuit?
Smart/sports watch?

Anybody wearing a cardiac pacemaker nearby?

What country are you in? Near any military/naval installations?

Is the television unplugged? Some newer TVs use that frequency as part of their DSP circuitry.

Is the frequency there when the active crossovers are turned off and removed from the signal chain?

That has a lot of noise on top of the 5333Hz blip, MusicScope (a great app!) spectrogram attached.

Ok I’m in Singapore…power is generally stable but could be polluted with who knows what.

Military who know what they hide out there, there is a camp nearby but have had this sound in one form or another in another location too over 10 years ago…all gear pretty much has been changed.

No pacemakers etc nor TVs on either. AC was off too when everything was off. AC Was on at the time of the recording

I can’t hear it at the speakers…my wife can…I can hear it on the recording…might just be below my threshold at that level.

Recording was in a noisy room so ignore the background noise and was recordered hand held a few cams in front of the tweeter with an iPhone

Seems not to be related to volume settings. Hard to hear when music is playing. Is not present when the system is off, and other things in the room remain on

Doesn’t appear to be present on tv speakers or other small speaker setups like Oppo sonica speakers when idle, or RPi with dac amp hats when music is not playing but these could have auto muting and idle shutdown

I’ll post a system components list at some stage too, but as I have said it’s a problem that has been around over 10 years in 2 different consecutive homes and many different equipment changes.

My guess is that there’s a VLF transmitter somewhere nearby. There are all sorts of weird VLF signals around used for secret comms, especially to ships and submarines.

That being the case I’m wondering how one would resolve it. Anyway I am still trying to determine what is letting it in. Amp or pre or Active crossovers. I built the active crossovers my self so maybe can build a notch filter at that specific freq to clean it, but will need to do this on 3 systems with more than 10 channels currently. Might be that it’s between 2 of the crossover points too…tweeter and upper mid on one system - the LX521’s Diy from LinkwitzLab.com

Very nice speakers, a fellow DIY-er I see :).

No idea how to resolve that yet (would of course depend on the exact nature of the cause too, which is not yet certain.).

Your active crossovers : are those digital in nature ? If so, are you using its clock as a timing for another process than audio processing ?
(For example, every 9th tick it is triggering something else ?).

I can’t help but notice, that 5.33kHz is such a nice subharmonic of the very common sampling rates 48/96/192 etc kHz…

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Analogue ASP no digital after the DACs but there more than a few DACs in the house.

OK so gave up chasing in the ASP and big rig and went back to battery run Oppo HA-2 headphone DAC/AMP with Line in and a 3.5mm to RCA lead to hold onto the input pins using my body as an antennae…loads of 100Hz as expected I fully expected this 100Hz mains frequency) but a symphony of clicking and buzzing and 5333Hz when ever I placed it near anything on the mains while holding the RCA input pins is not what I would expect. This is full volume on High Gain selection to IEM’s…so now to go really mobile outside the house and see where this interference is present…down the building corridor and out into the other areas where there is power in the public areas, lifts, street lighting etc etc

Maybe its a flakey earth as I have never really liked the way has looked outside my apartment just cobbled to water pipes that go who knows where…

The mystery continues…but at least its not my gear making the interference I hope…will be downing the whole house to see what breaks the noise too.

I might try to inject the headphone line out into an ADC and get this recorded again without the mic issues.


So, the question is whether you can get rid of the 5333Hz with power filtering, or it is being picked up by an unshielded signal cable somewhere in your system. Any chance you can make everything balanced/XLR in your low-power analog signal path before you invest big on power cleaning?