Computer background noise and FM radio

[dave2010]

A couple of days ago we were planning a Zoom session. A speaker wanted to play violin to the assembled group. We wanted to check out and hopefully avoid any problems with the session, so we connected several computers and iPads together via Zoom in a test.

Once we'd eliminated the obvious things, such as acoustic feedback, and tried using headphones to mitigate against high frequency oscillations we tried to simulate the sound of music by tuning to radio stations using a small FM portable radio - which we've had for years - and which was in the past very good.

As we tried this, I realised that the FM radio was highly likely to pick up noise from the computer, and indeed that was the case.
In the end we were able to do a fairly poor test, but it required very careful siting of the radio on top of a bookcase - the best compromise between audio - distance from the computer microphone - and getting the FM signal without horrendous background noise.

The test did show up some issues, and the generally poor quality of the Zoom connection - even poorer than the limits of the FM radio would allow. It was useful to do, as we were able - mostly - to optimise the audio in the final event, and the speaker was aware of possible problems, so quite happy to retreat slightly while playing in order to avoid the input overload on the send side of the link.

FM radio at its best can be acceptably good, or at least pleasant to listen to, but I wonder if all the computer generated interference these days is rendering it considerably less viable these days.

So many of us use computers that I think the overall background level of noise must have gone up, and can disrupt services - such as FM radio.

Comments?

[Geoffrey Stevens]

I still use my FM tuner a lot. It's in my study with my desktop computer + various other computer bits.
Yes, the computer does generate 'noise' - my computer is pretty standard with a 'normal' power supply.

I've done various things to minimise interference:
The tuner and amp are on a different mains socket to the computer. The tuner/amp use a Tacima power bar (not sure how much diffrence this makes).
Ferrite cores on mains cables - the most effective was the one placed at the computer end of the computer mains cable.

When I'm listening casually (probably working on the computer at the same time), I don't notice any interference. When I do any 'serious' listening (e.g. Proms concert) then I switch off the computer. I then get improved sound quality and no noticable noise at at. A good FM broadcast (on R3) still provides (for me) a very pleasing listening experience.

Please also note that I use a Magnum Dynalab ST-2 aerial, located at the far end of the study - works really well.

My 2p worth.

Regards,
Geoff

[dave2010]

I do wonder whether with so many of us now using computers that the overall background level of noise has had a really bad effect on FM or other forms of communication.

Re radios generally I noted that Lidl are now advertising a DAB+ radio for next week's offerings. AFAIK the UK doesn't do DAB+ yet, but maybe I blinked.

[jahsavage]

Hi Dave

My house has good quality WiFi and computers everywhere but the biggest source of interference is the Gigaset land line remote. I have it on a shelf near the HiFi. It induces hum and horrendous pops in my Groove SX phono amp and an Audio Design pre-amplifier, to the point where I have to switch the phone off when listening to audio. Fortunately my EAT Glow phono amp is almost immune although if I listen careful I can tell there is a very low level hum pickup.

I have an Intel NUC computer I use for Roon, this sits right next to my phono and preamplifier but does not generate any audible interference.

[Mr. C]

Welcome to the wonderful world of SMPS!

[GrahamS]

I have recently "discovered" the radio stations included in the Sky Q menu and have been very impressed by the superb audio quality I get listening to either Classic FM or BBC Radio 3. The signal path is: Sky Q satellite box to Samsung smart TV via HDMI cable, TV optical out to an eSync 24 bit DAC digital to analogue converter, (which cost a whole £12.95) then to the NAD amp via Fisual Rio RCA cables, then out to my Wharfedale Diamond 230s. I admit that my hearing is not what it used to be but I can still discern good from bad. This is good. I have no idea which DAC chip is in the eSync box, but whichever it is, it works.

[Macca]

I sometimes listen to my FM tuner while working - two computers on - without any issues. Although the tuner is a good fifteen feet away from either of the PCs and uses a rooftop aeriel.

According to this https://spin.atomicobject.com/2020/05/19/zoom-music-audio-quality/ Zoom uses a processing algorithm to eliminate high frequencies in order to reduce feedback issues so that might be part of the problem - there seems to be ways round it.

[dave2010]

Hi Dave

My house has good quality WiFi and computers everywhere but the biggest source of interference is the Gigaset land line remote. I have it on a shelf near the HiFi. It induces hum and horrendous pops in my Groove SX phono amp and an Audio Design pre-amplifier, to the point where I have to switch the phone off when listening to audio. Fortunately my EAT Glow phono amp is almost immune although if I listen careful I can tell there is a very low level hum pickup.

I have an Intel NUC computer I use for Roon, this sits right next to my phono and preamplifier but does not generate any audible interference.I have been aware of problems with various devices for years. I used to be sceptical about mobile phone interference, which is supposedly a problem in hospitals. Actually I think that mostly there isn't a major problem in some areas of hospitals, but in some areas where specialist equipment is used, it can be a very serious problem.

I once worked in an office in which there was a definite interaction between my desktop computer and mobile phones.

Very recently mrs d observed that sometimes the radio links get blitzed whenever the microwave oven is turned on. This is something I knew to be possible, but I was surprised she'd made the connection.

I think there could be a lot more interference background now than in the past, but most of the interference will be at frequencies which don't have the same bad effect as a motor bike with a poor interference suppressor.

[dave2010]

I sometimes listen to my FM tuner while working - two computers on - without any issues. Although the tuner is a good fifteen feet away from either of the PCs and uses a rooftop aeriel.

According to this https://spin.atomicobject.com/2020/05/19/zoom-music-audio-quality/ Zoom uses a processing algorithm to eliminate high frequencies in order to reduce feedback issues so that might be part of the problem - there seems to be ways round it.Hi and thanks.

Re FM - if you are using a rooftop aerial and the cable is screened all the way down to the tuner your sound will probably be OK - as you state it is. Portable sets, which is what we used for our test, tend to pick up the computer interference if within a couple of yards of the computer - which is what we had. It was a compromise between the computer microphone picking up the radio sounds, and taking the radio too close to the computer.

It was worth doing the test though - as it did highlight some potential problems with Zoom in advance.

Thanks for the link to the page about optimising Zoom audio for performers. It won't work for everyone I think, and is quite involved. We noticed we can get feedback even with quite long distances involved (over 5 metres) if there are multiple active devices - high frequency feedback is quite easy to induce.

Apart from eliminating any possible methods of feedback, turning off the automatic gain control for the mic input helps - presumably for some of the reasons mentioned. Also don't use a large amount of background noise suppression.

[jahsavage]

Hi Dave

Your description indicates the interference is via transmission from the computer. If your radio is mains connected the interference may come via the mains power lead. Although its overkill for your use PS Audio do some wonderful power supply products you can use with your Hi Fi or computers.

Paul