What is the source of this audio? Some sort of communication issue is high on my list of possible causes. Has your network changed recently? Are your SONOS units wired or wireless? Describe your network and SONOS system for us. What model router are you using?

BRIDGE would be inappropriate because of its age.

Hi @buzz, I'm not very technically minded so please forgive me if I don't provide all the info. The router is a BT Smart Hub 2. My units are wireless but if wiring the sub would help I'm happy to do that. I recently had full fibre installed but the issue was happening before then. I'm not sure if it's a problem with my set up or the audio file even . Please let me know if there's any more i can provide that would help in finding a solution. Thanks for your time

How are you sending the 40Hz to the FIVE? Is this a computer file? App? Online Service?

Maybe wiring the SUB will help. As a test, at least temporarily wiring both might help, even if you need to physically move the FIVE in order to do this. Keep a log of events. Does this always happen? Certain days? Certain hours?

Within 10 minutes of an “event” submit a diagnostic and follow up with SONOS support. SONOS staff has access to data that is not available to us. Sometimes staff will reply here. As I mentioned, I suspect communication issues. These leave tracks in the diagnostics.

Hi @buzz, I submitted the diagnostics to Sonos but they weren't able to help. The fact that the sub is out of warranty didn't help either.

It's an mp3 file that I've uploaded to YouTube Music and I play it through the Sonos app on my Samsung Galaxy S9. 

I did a test this afternoon and wired the sub in. I didn't get the warning message about the file not being encoded properly. However, there was too much background noise to assess if the 'pulsing' is still there. I'll wait until the dead of night when it's silent and the infrasound is at its worst to see if it works to mask it.

Is there any possibility you can host the file locally, using the Sonos Music Library option?

Taking the unreliable connection to YouTube out of the picture would be good.

Hi @Stanley_4 , thanks for your reply. I used to play it directly from my fone before that option was removed and the same thing would happen then. I've been having this problem for a while . 

That support agent was not very helpful. Support can determine if the issue is local, remote, or a combination. Post a confirmation number here. Hopefully a Community moderator will look at the diagnostic.

How long does your file play before it must repeat? Are the glitches associated with the repeat event? Are you using crossfade?

Personally I’d use a hardware oscillator, not a file or App for this task.

If you are the DIY type here is an option.

Here is an interesting, inexpensive gadget, be sure to view the videos, because it has some quirks.

I have no experience with the above and there are hundreds of other products.

So no other option to host it locally?

I’d suggest a Raspberry Pi Zero set up as an SMB NAS then. Not really hard to set up and as they are using them in a lot of schools a kid or grandkid could likely set it up for you. Ready-built stuff is going to be a lot more expensive but less initial effort.

https://stan-miller.livejournal.com/940.html

Hi @Wendyzx6 

Welcome to the Sonos Community!

Sorry to hear of the troubles you are having with your Sub - I can see you’ve been putting up with this for quite some time!

However, given the info that you provided in your last communication with our technical support team, I recommend that you find/create a new file with the 40Hz sine wave and re-upload it to YouTube Music, replacing the file that you are currently using.

I hope this helps.

I'm pleased to say I think the issue is sorted. I've wired in the sub and haven't experienced the same issue again. I'm assuming it was an issue relating to poor WiFi signal.

Hi @Wendyzx6 

Great! Thanks for updating the thread!

@buzz @Corry P @Stanley_4 

Sorry folks, spoke too soon. The pulsing and error message have returned despite the sub being wired in . The only thing that stops the pulsing is turning up the volume to approx. 8 which although quiet in terms of daytime noise levels, is loud at night time. Whilst it's masking the LFN I can hear, it's too loud to sleep . 

The file I'm playing through YT Music is an mp3 file. Do you think it would make a difference if it was saved as a wave file with no audio compression?

If you play a different source are there any issues?
From my seat in this drama, I can’t yet rule out a problem with the file, the YouTube feed, the network, FIVE, or the SUB.

Is anything plugged into the Line-In Jack on the FIVE?

Let’s rough up the SUB a bit. Pick up one end of SUB a quarter of an inch (6mm) and drop it. Take care that SUB will not be able to roll over on you, First do this with power removed. Other than the thump on impact, there should not be any major stress sounds.  Now that you are familiar with the “thump”, power up SUB and repeat the drop (no music yet). The “thump” should be unchanged. Finally, play some music and repeat the drop. You should only hear the music added to the “thump”. By now you are very familiar with the “thump”. If there is a music dropout or obvious noise that doesn’t belong, there is a mechanical issue inside the SUB. A healthy SUB will not care about any of this.

You can repeat this abuse with the FIVE. You don’t need to drop the FIVE, you can slap it with an open hand. There should be no unusual response from SUB as you slap the FIVE.

Since we have not yet proven the 40Hz file is OK, I don’t think it should be used for this test.

Hi @buzz, thanks again for your reply. I'm not aware of any issues with any other audio file but this one is fairly unique in that is consists solely of a 40hz pure sine wave tone which is played at a very low volume so that it is just audible. No.part of it requires tk co.e through the FIVE so I imagine if it's a hardware issue, it'll be the sub. I can confirm nothing is plugged into the line-in jack on the FIVE. 

I'll give what you suggested a go this evening and see if there is any change in the sound which could indicate a mechanical problem .