Topic: Is system noise a thing of the past, which can usually just be ignored?

[Ozpeter]

Today, almost on an impulse when I found myself on a very still day in the deserted and quietest countryside park I know, I recorded about 5 minutes of birdsong using my humble Zoom H2essenial.  This isn't about that recorder so much as about any reasonable modern portable recorder these days - that's just the one I had in my bag.

The birdsong was actually more or less inaudible to my bare ears while the recording progressed.  I was a bit annoyed the birds were being unhelpful.  But when I used Audition to first play the recording unchanged, and then normalised (+30dB), I was staggered to hear that birds were actually singing all the time, and I could even hear the decay of the reverberation of their calls once the gain was raised that much.  Yes, I could hear a fair bit of background noise instead of the previous near-silence, but it sounded to me like environmental noise rather than system noise.  It sounded "out there" rather than "in there".

This was a good test showing how raising digital gain when recording in 32 bit float these days is pointless - all possible detail was actually in there on the almost flat waveform -  but also that it's hard to imagine the circumstances where system noise would actually be a real world problem.  Certainly not in the tapers section at a rock concert. This noisy world's environments are the problem, not the recorders!

I put my experiment together in a YouTube video on my unmonetised channel.  If anyone cares to check it out and tell me that I'm totally wrong, here's the link.

https://youtu.be/eHCQG3hBYrY

[VibrationOfLife]

Noise floor is definitely a real thing.  Don't discount it.

[grawk]

That you heard noise with only 30db of gain says noise is still an issue. To know if it’s from the recorder or environment, using an analog preamp in front of the recorder and see if it gets louder. Recording silence in the quietest area you can find with varying levels of gain from -10 to 60db would be an interesting test.

[Thelonious]

I recorded an acoustic show from the back of Het Concergebouw last November with mk22>riotbox (no gain added)>F3 and there was system noise in the recording. Now the show was VERY quiet (someone shuffling in their chair a few seats away was much louder than the quiet parts of the music) but I was actually surprised and wished I had brought my SD MixPre 6ii with me as my sense is the preamps are quieter on that. I could have also added gain at the riotbox but I'm unsure if that would have risked the audience noise, which was orders of magnitude louder than the quiet parts of the music, would have overloaded the mic pres if I did so...

I raise this extreme example because I've never thought of the F3 preamps as adding noise but, in this extremely quiet recording situation, it was there and I believe it was from the mic pres as opposed to the mics or the HVAC etc.

So I do think it's still an issue but I would suspect it's far less of an issue than it would have been 10 years ago...

[Gutbucket]

Determining which noise source defines the audible noise-floor of a recording can be challenging.  Grawk's proposed test is a good one for discerning the increased noise floor of recorder vs preamp at various settings, but may not help much in determining what defines the lowest noise floor when using more optimal settings.  Is it the environment, microphone self-noise, preamp, recorder's analog input stage?

Of course system noise matters, but we can manage it pretty well with proper attention.  There is no question that the dynamic range of inexpensive gear has improved significantly over the years. That's good. Yet I wonder if loss of awareness about the fundamentals of good gain structure may end up being an unfortunate byproduct of the widespread adoption of 32-bit float recording.

Years ago I put a good amount of effort into optimizing the gain structure of my 24-bit stealth rig to achieve the maximum possible dynamic range. I never measured, but I think I got it to around 100dB or so which is reflects the dynamic range capability of the mics.. and probably the real-world dynamic range of the 24bit recorder I was using as well. That process started with choosing the appropriate mic sensitivity, then determining the optimal input setting on the recorder, then carefully tweaking the fine gain trim of the preamp such that I could choose between three gross gain settings when recording any music performance.  I mostly used just two.  The most sensitive setting was appropriate for the most demanding recording environments in terms of noise-floor and overall dynamic range, and was determined by my desire to keep the impulse peaks of the loudest applause from a potentially over exuberant person sitting immediately adjacent just below clipping.  That was the practical constraint, and at that point it was still not a simple task to determine if either microphone self-noise or HVAC defined the noise-floor of the recording.  I later determined that the noise-floor was indeed dominated by the ambient noise-floor of the performance space, which included a couple modern purpose built, highly acoustically isolated classical music halls which are the quietest places I've recorded music with an audience present. 

I used the second, lower gross gain setting for most PA amplified material, where the peak SPL of the music regularly exceeds that of adjacent applause impulse peaks - the specific setting determined somewhat more arbitrarily via experience.  In the third lowest gain position, the highest SPL the recording chain was able handle was determined by the SPL limitations of the microphones.  That one useful for especially loud material, but one I rarely used. 

Three gain settings- highest determined by the max SPL of the environment (with the noise-floor falling where it may upon optimal gain staging, fortunately also determined by the environment), the lowest being determined by the SPL limits of the microphones (the noise floor in those decidedly non-quiet situations pretty much always being ambient audience noise), and one somewhere in between that suited most amplified music situations.  It required an external preamp to do that.

With a goal of eliminating the external preamp among other things, I'm still trying to rebuild an equivalent performing rig using newer recorders, yet can't quite do so yet while achieving the same specs.  Passing off all gain-staging to the manufacturer of the recorder would be convenient, but is not quite there yet for me.

[capnhook]

Don't know if you gents can use an improvement in your workflow, but here's what works for me...

Sample the system noise in RX (you DID a nice long pre-roll and recorded the room and your setup at idle, eh?)

Subtract the noise you found, first thing before mixing

Noise is gone, a thing of the past..

[beroti_music]

I recorded an acoustic show from the back of Het Concergebouw last November with mk22>riotbox (no gain added)>F3 and there was system noise in the recording. Now the show was VERY quiet (someone shuffling in their chair a few seats away was much louder than the quiet parts of the music) but I was actually surprised and wished I had brought my SD MixPre 6ii with me as my sense is the preamps are quieter on that. I could have also added gain at the riotbox but I'm unsure if that would have risked the audience noise, which was orders of magnitude louder than the quiet parts of the music, would have overloaded the mic pres if I did so...

I raise this extreme example because I've never thought of the F3 preamps as adding noise but, in this extremely quiet recording situation, it was there and I believe it was from the mic pres as opposed to the mics or the HVAC etc.

So I do think it's still an issue but I would suspect it's far less of an issue than it would have been 10 years ago...

Off topic, sorry for that but since I have mk22's too; why did you use them at the back of venue? Isn't it better to use mk4 or mk41 in that spot? I use mk22 for when I'm close or in open air. Curious to hear about your motivation!

[grawk]

I’m not who you asked but I use wide cards whenever the sound where I’m setting up is closer to ideal. In the right room with the right engineer that can be farther back. 

[aaronji]

It was in the small room at the Concertgebouw. It was pretty intimate, maybe 400 people.

[Thelonious]

I recorded an acoustic show from the back of Het Concergebouw last November with mk22>riotbox (no gain added)>F3 and there was system noise in the recording. Now the show was VERY quiet (someone shuffling in their chair a few seats away was much louder than the quiet parts of the music) but I was actually surprised and wished I had brought my SD MixPre 6ii with me as my sense is the preamps are quieter on that. I could have also added gain at the riotbox but I'm unsure if that would have risked the audience noise, which was orders of magnitude louder than the quiet parts of the music, would have overloaded the mic pres if I did so...

I raise this extreme example because I've never thought of the F3 preamps as adding noise but, in this extremely quiet recording situation, it was there and I believe it was from the mic pres as opposed to the mics or the HVAC etc.

So I do think it's still an issue but I would suspect it's far less of an issue than it would have been 10 years ago...

Off topic, sorry for that but since I have mk22's too; why did you use them at the back of venue? Isn't it better to use mk4 or mk41 in that spot? I use mk22 for when I'm close or in open air. Curious to hear about your motivation!

I have the MK22s and the MK41s. In general, I prefer the mk22 for bass response and overall image depth in a good sounding room. The room in question was the chamber room at Het Concergebouw in Amseterdam. Part of what I wanted to capture is how the room sounds, which was really great and it lends a sense of grandeur that I think was part of the performance. I did not know where I would get to set up in advance, nor had I anticipated the sound level of the music to be so low relative to the audience even though I have recorded the same band at SF jazz in what is an opposite style of room (SF Jazz almost like a studio, the Het Concergebouw designed to carry sound of unamplified instruments to the back of the room). I like the sound of the recording, and while a hyper cap may have sounded "cleaner" (less room) it wasn't what I was after. The noise issue, which I hadn't anticipated as I have never recorded something that quiet with that rig before, would have remained. The reverberance in this room gives the recording a unique sense of space.

I did ultimately use noise reduction in RX. The challenge is that in this room, you can hear literally any movement in the room making getting a really clean moment almost impossible (much to my surprise and disappointment). The result was not bad but did not allow me to cleanly reduce the noise to being a non issue, but did increase the level I can listen to the recording significantly (and likely above the volume at the mics location in the room).

[Billy Mumphrey]

I mean, how long until we're all using mics with DIGITAL amplifiers (ie Schoeps CMD 42)? Isn't this the current standard for lowest noise floor? I'll try to dig up DSatz's post explaining why CMD 42 amplifier is so quiet....

[beroti_music]

Thanks for the replies on the wide cards and mk22s!

I like the bass response of the mk22 as well.
Its a beautiful sounding cap. But since I do stealth video often as well, I often find myself at the back of the venue, hence the question

[Thelonious]

Thanks for the replies on the wide cards and mk22s!

I like the bass response of the mk22 as well.
Its a beautiful sounding cap. But since I do stealth video often as well, I often find myself at the back of the venue, hence the question

Yes, this was a smaller venue, with incredible acoustics, so it wasn't like being at the back of an arena or something like that where the reverberant sound would strongly detract from the quality. Off topic, I have started doing some video here and there so expect a PM shortly so I can pick your brain. 

[grawk]

I mean, how long until we're all using mics with DIGITAL amplifiers (ie Schoeps CMD 42)? Isn't this the current standard for lowest noise floor? I'll try to dig up DSatz's post explaining why CMD 42 amplifier is so quiet....

Once they put that in something the size of a cmc1

[Gutbucket]

I mean, how long until we're all using mics with DIGITAL amplifiers (ie Schoeps CMD 42)? Isn't this the current standard for lowest noise floor? I'll try to dig up DSatz's post explaining why CMD 42 amplifier is so quiet....

Don't get me wrong, that's great, I just don't think a noise floor that low is particularly important for "what we do".  The mic's self-noise really only needs to be somewhat lower than the noise-floor of our quietest recording environment.  As I describe above, even in the "quietest" live performance scenarios I've encountered, the ambient noise floor of the hall with church-mouse quiet minimal audience in attendance still exceeded the self-noise of the mics.  That was using DPA 4060 with a self-noise spec of 26 dB(A) re. 20 µPa / 38 dBs ITU-R BS.468-4.  I suppose that really shouldn't have surprised me but it did. Sure, some folks here may be recording in situations quieter than that (beroti_music maybe?, Peter's nature recordings), but its going to be a rare at most of the live performances that folks at TS are recording.

Subtract the noise you found, first thing before mixing

This is the second part of the discussion - using noise reduction afterward.. regardless of the source, which we don't really even need identify.  Requires a close listen and careful touch to assure doing more good than harm, but noise-reduction algorithms have grown better over time and will continue to do so.  Kev, I've not done a whole lot of noise-reduction myself and have a practical question for you- When you're using a noise sample from the pre-roll section to train the noise reduction algorithm in RX, how much does the presence of audience noise and chatter in the sample mess with its effectiveness?  Seems the best training sample would be just steady-state room and signal-chain noise without the interference of that kind of non-steady state audience noise.  Does it work best below some threshold level of chatter?  Do you still bother if the room is already "human noisy" when the pre-roll starts?  I'm just thinking that there are plenty of times when there's minimal audience noise, but its rare to have none unless getting in early with the band.  It is considerably easier to get good noise-samples at classical gigs where folks traditionally quiet themselves just prior to the start.

[Billy Mumphrey]

...I just don't think a noise floor that low is particularly important for "what we do".  The mic's self-noise really only needs to be somewhat lower than the noise-floor of our quietest recording environment.

I agree. Outside of classical music and nature recordings, you're much better off putting your money and energy into other aspects of the recording process IMO. For any newbie's reading this, don't hesitate to grab that $60 Tascam Dr60d on marketplace. It will be just fine for anything moderately loud (and still acceptable for quieter stuff *shrugs*).

With that being said, I still wanna hear a rock (or loud music) audience recording with CMD 42's (hopefully into a PR-4?) and crank it on my home stereo and see what my ears tell me. One day a 4-mic CMD 42 (or equivalent) setup > 4-channel AES3 recorder will be my go-to rig. Especially if they make a CMC1 version like grawk mentions.

[capnhook]

...I just don't think a noise floor that low is particularly important for "what we do".  The mic's self-noise really only needs to be somewhat lower than the noise-floor of our quietest recording environment.

I agree. Outside of classical music and nature recordings, you're much better off putting your money and energy into other aspects of the recording process

Billy Mumphrey, to your point of putting your energy into other aspects of the recording process, for me it often involves getting set up early to get a baseline of the room noise, and maybe hear the HVAC run

No solution for the chompers yet, Lee 

[Ozpeter]

That you heard noise with only 30db of gain says noise is still an issue. To know if it’s from the recorder or environment, using an analog preamp in front of the recorder and see if it gets louder. Recording silence in the quietest area you can find with varying levels of gain from -10 to 60db would be an interesting test.

I suppose what I am testing is the standalone system - the demonstrable system noise produced from one end (built in mics) to the other (digits).  To do that in such a way as there would be zero chance of the mics actually detecting any sound in the 'silent' environment is not simple (without perhaps a high tech soundproof room).  And that's what is needed to be sure that any noise heard is system noise, not environment noise.  As the gain and thus the recorded noise is fixed in the 32 bit float system, there is nothing to adjust.  The recorder just assumes it's confronted by a rock band and it's been configured appropriately by the makers.  What surprised me when running my test was that despite that configuration, the reverberation of the originally inaudible bird songs (inaudible by me on location) was clearly audible when 30dB of normalisation was applied.  Not just the bird calls, but the reverb thereof.  That sound must be close to the quietest sound one could normally encounter in life.

That scenario would, or should, be improved by connecting external low noise mics and preamps etc, indeed.  But it would be interesting to demonstrate that even using inexpensive built in mics, noise is not a practical problem in most circumstances.  Not all, of course.

I will see if I can devise another test... put the recorder between two mattresses in a countryside bedroom at 3am...

As for using noise reduction, I did actually also have the recorder set up with its built in AI NR being applied to another pair of tracks.  That did drop the background noise (system noise or distant environmental noise, whichever) by 12dB, but it did subtly mess with the birdsong when normalised.  How well it might work when recording music in an air-conditioning compromised performance space (for instance) I don't know.

[Ozpeter]

Actually, the test should be fairly simple.  Record 'silence' in a room.  Then do whatever is possible to reduce the silence further by burying the recorder under something suitable.  Then put the two recordings into one file, normalise as one, and see if the part with the recorder 'buried' is quieter and in what way.  If the recorded noise reduces, it must be environmental.  If it doesn't, the noise must be self noise.  In fact the result might not be that definitive but it might reveal in the quality of the noise what is environmental and what is system.  I could have done that during my original test by simply getting into my car and recording the external 'silence' in there, to compare with what I had recorded outside.  No, not with the engine running...

[Ozpeter]

OK, I've tested along those lines. 

I made an H2e recording with the device lying on the bed in a quiet room.  Then I put a duvet, rolled up, over it, and recorded some more.  Then I took the recorder into the toilet adjacent to that bedroom, which has no windows, and recorded some more silence.  Finally I put the duvet over the H2e in the toilet - yes, really - and made a final recording of silence.

Playing those back, normalised equally, I could hear no difference with the duvet over the recorder, compared to it not being over, and actually to my surprise there was a very slight increase in noise in the toilet.  All in all, I would say that what I recorded was very close to 100% system noise.

Next, I put together a plot of the noise in the park and the noise in the bedroom.  With luck it is attached.  The noise in the park is in red.  In the bedroom, probably just system noise, it's green, and it is a smooth curve indicating that no significant variable environmental noise was present.  Note that the two lines converge at 9kHz.  The noise from the park, which included environmental noise on top of system noise, is a maximum of about 9dB greater than in the bedroom.  The level of system noise goes down from about -72dB at 400kHz to about -101dB at 20kHz.  Remember that the recordings were made at the same analog level, as it's not adjustable.

So having now got a recording which I'm confident is system noise from this device, I went back to considering under what circumstances it would matter.  I spent some time in Audition multitrack, overlaying commercial classical recordings with the system noise.  I chose works which have significant dynamic range, and finally settled on Taverner's choral work "God is With Us", where the final chord in the organ is full scale loud, and where other parts are pianissimo.  I adjusted playback to threshold of pain when playing the end of the work! 

Interestingly, after the final chord, there are at least ten seconds of what seems to be 'live silence' before the original track is faded.  With the H2e system noise added, I couldn't hear that noise at all.  If I raised the H2e noise playback level by about 6dB I was just about able to hear it - with headphones, and remember the music peaks were maximal.  With the H2e noise muted, the original recording's noise in the end silence was about 12dB louder than the H2e noise on its own, though it may well have included some environmental noise from the cathedral where it was recorded.

So, I go back to the suggestion that even this inexpensive modern recorder's system noise (and that from other such devices) is unlikely to be a significant problem, so long as when using it you make sure that the signal to noise ratio is optimal.  You can't do that with digital gain setting, but you can do it with positioning.  Make sure using appropriate proximity that the level reaching the mic, the signal, is as high as possible, with the proviso that when using the device for acoustic recording and the location's reverberation is important, you are not too close.  The end result, in terms of system noise audibility, should be fine in the context of the likely uses of such a device.  And if it's amplified music, I would be really surprised if system noise is any kind of problem at all.

[Gutbucket]

Nice real world test, Peter!

Kevin, yeah on the chompers.  What I'm wondering is if you've found the samples you use to train the nose reduction still useful if they contain ANY amount of background conversation or other transient noise, or if they need to be completely clean of all that to be useful, containing nothing else but the steady state noise being targeted.

Perhaps the details are best discussed in a thread on noise-reduction. I'm just trying to get a rough idea of what works for you and what doesn't based on your experience with it as a regular part of your process.

[Ozpeter]

Before Kevin gets a word in (and before I head to bed), the "AI NR" on this little Zoom device samples the ongoing noise just for a couple of seconds before it's ready to record, and I imagine it is aimed at room environment noise - and its own self noise, which is also lowers by 12dB.  But as I said before, I wouldn't use it for music.

Lastly, I just did a quick test on the digital level settings they recently introduced.  All as expected.  The default "70" level, the max "100" level, and the unintuitive "1" level, which produces what looks like a flat line recording, all amount to the same thing when normalised - and the setting chosen has no bearing on system noise in relation to signal level.

[VibrationOfLife]

Doesn't Curtis have an xlr plug that sends in a frequency he can record and then just pull it up in software to reveal self-noise?

[Ozpeter]

It's a 150 ohm resistor connected over the relevant pins.  But my particular interest is in noise including the noise from the built in mics themselves - which is quite tricky to assess accurately.

[VibrationOfLife]

I've only used built in mics for interviews.  Seems wholly inappropriate for live concert recordings.

[Ozpeter]

I've only used built in mics for interviews.  Seems wholly inappropriate for live concert recordings.

I guess the appropriateness depends on various factors.  External mics are very likely to provide the best outcome depending on which ones are used, but practicality, cost, and the time available for post-production have a bearing, it seems to me.

Some months ago I came across a YouTube channel where college concerts are presented.  By chance I noticed that in the video descriptions, use of an H2e for recording the audio was mentioned.   Having listened to some of one event, frankly I found it hard to believe that a single H2e was being used to record a public performance by a quite large concert band.  So I asked the channel to confirm that they really had recorded it that way, and they said indeed they had, although some post production was involved.  Put it this way - if they hadn't said it was just that little recorder, it would never have crossed my mind (or my ears) to think that it wasn't done using a much more sophisticated method.  But maybe I'm easily fooled.  You can check it out here -

https://youtu.be/JcEgTGeMJKE?si=wQbdvsU0RQdit61q

Would you have thought, "ugh, that's just a cheap portable recorder" when hearing it?  (If you care to listen to a sample).

[VibrationOfLife]

I randomly recorded this while walking down the street.  I set my recorder on a barrel in an 800 person outside tent.  I get it.  Wasn't ideal, but at least I got to hear and record that story.  I just wouldn't intentionally do it.

https://archive.org/details/old-el-paso-tamales

I did listen to the entirety of that performance.  It sounds like shit, or more accurately a mic slapped on the top of a video/mirrorless camera by a dad.

So I think we both proved the point evidentially.

[grawk]

to get things back on topic, for most of what we record, using the hardware typically used by members of this fine forum, system noise is rarely the problem that will make or break a recording. 

Sometimes with quiet sources, you'll hear the mechanical noise floor when using digital gain to bring the volume up.  System noise will disappear behind other considerations if you put analog gain in front of it, then you'll hear the self noise of the microphones, the base noise of the room, etc. 

With certain inexpensive 32 bit gear, the built in microphones will probably be well matched to the recorder, so noise will likely not be an issue.  Spacing, resollution, off axis response etc will come into play, but the best recording is best, but the only recording sometimes has to be good enough.

[Ozpeter]

I randomly recorded this while walking down the street. [...]  It sounds like shit, or more accurately a mic slapped on the top of a video/mirrorless camera by a dad.

So I think we both proved the point evidentially.

Well... to me it sounds like I would have expected under all the circumstances from any reasonable recorder - the sound quality (IMHO) would be dictated by the sound quality of the PA system, plus your distance from it possibly coloring the audio.  Not a trace of system noise detectable by my personal ears.  But maybe by others blessed with better ones?  (Fun to listen to, thanks!)

I guess as one who doesn't do proper tapers section recording (so why am I here?!) my feeling is that the quality of the PA system is always going to dictate the quality of the recording at least as much as the recorder itself (with the proviso that I can imagine PA systems outputting low frequencies which would challenge many lower cost devices).