Some odd little distortions

Hello, friends. Hope you’re all well.

Here’s a funny thing I was wondering if someone might have an idea about. I’ve done a few audiobooks and occasionally I find that I get an odd ‘ring’ or other wobbly maybe harmonic distortion but only on certain words. I’m using a Rode NT1 and Rode AI-1 either feeding straight to my Macbook/Audacity or to my iPad vis USB and then process and edit in Audacity later.

Recording on either workflow will - only occasionally - give me the same reverbs. Now I’ve got quite a resonant voice and the NT1 has a metal popshield. I’m wondering if I’m hitting some resonant frequency and making the shield itself vibrate?

Heres a dropbox folder with some samples from recent records that were made directly to the Mac. All are .wavs clipped directly from raw recorded audio. Each clip name is the word that has the wobble on it. Is there anyone here who can either tell me what the cause might be or suggest something to EQ it out when it does pop up?

I’m recording in a treated space that has let me produce a few audiobooks and other work with no troubles so it’s not that. I think it’s actually ME!

My thanks to you.

Audacity 3.0.2/Mac 10.11.6/Rode NT1+RodeAI-1

I can hear resonance on “arounD eight years ago” …

Audacity’s spectral editing tools can give some improvement …
''around EIGHT years ago'' (resonance ~500Hz & ~1500Hz).gif

A nylon mesh popshield, and/or clown-nose foam, are less likely to resonate than metal …

https ://

Hello, Trebor.

Thank you for your reply, I’d have pinged you back sooner, but I see I had notifications for this topic turned off. Oops.

I can certainly see that there is a difference in the two "around"s and that little extra can be seen removed in the spectrograph, thank you for the gif. It looks like this resonance(?) runs from 300Hz all the way up to 2KHz. Did you use the spectral edit multitool as a notch filter to remove that? When its popped up in the past that’s how I’ve dealt with it but the ripples seems to be rather broad (well, across 1.7K, so that’s pretty broad to me!) so I’d do multiple notches to try and clear out where I can see the flares on the speccy. Did you use the notch filter capacity or another method like shelf editing pls? I’m not too au fait with spectral editing.

Also, sadly it does look like the look of the NT1 kit itself could be an issue! In the back of my mind I was always wondering and it was interesting to see it mentioned eslewhere as a minor issue. Thank you for the link. I assme in lieu of the proprietary pop shield this would suffice, if I kept the same distance from the mic.

I do have a fabric popshield somewhere but, maybe the foam baffle would do the trick on its own. Shame though, it does look really slick, but as the comments at gearspace say there is a sharpness on some sibilants - and I’ve only occasionally - noticed that myself. Looks like they should have spent a little more time on use rather than look!

Spectral edit parametric EQ , rather than multitool (notch filter).
Set to -3db, (it’s easy to apply it repeatedly with “Ctrl”+R to knock-back regions that are too strong).

I’ve had another go …

If it’s going to ring it will be on plosives, (e.g. “d” of around), or sibilance, as they have the greatest energy.

Thanks for that, Trebor. I’d meant to reply sooner but my Mac ate itself last week and I dicovered the only thing that hadn’t ever been backed up in Time Machine was the Application Support folder. Lost a lot and stuff an only barely managed to get things back to 50% so apologies. I’ll try that parametric EQ if I hear it again but I’ve dug out that fabric pop shield and am using that when I next get into it so maybe that’ll cut it back anyway. Also picked up that foam for the NT1 to make assurance double sure, as Lady Macbeth said.

well, i just did (on a long ‘U’ on ‘occur’) and well done that man! Shaved the top two ripples out using the parametric EQ and it sounds a whole lot better!

THAT being said, I was using the fabric pop and the clown nose at the same time. And the ripple was very low level but I guess I’m tuned to catch thse things now. Maybe it IS me! At least there’s a way to mitigate it now. Cheers again!

Unless you’ve swallowed a Jew’s harp, it’s not you.
Some part of the equipment is resonating, the mic itself if there’s no shock-mount, or a spring in a scissor mount.

Hello again, Trebor. Once more, sorry for the tardy reply, but real life bulged in again. Just to say, the mic is in its shock mount and I use a monopod as a mic stand, with isolation panels (Amaz*n cheapie) attached, no sprung arms in sight.

Since we chatted last I’m also using a clown nose as a fabric pop shiled ow as opposed to the metal proprietary one.

It’s on my mind again because I’m in the middle of cleaning up a BIG ripple in the work ‘profoundly’ in a current audiobook and have been for about 45 minutes.

…I mean I had to go to the dentist a while ago, but I don’t think he loosened that many teeth.

IMO not due to sound reflecting in the room, your room was already dead, (that’s a good thing),
it’s the mic or something attached to it.

The only thing remaining is to back-off from the mic so less energy is being delivered,
so that the resonance effect is less likely to occur.

Next recording I do, I’ll experiment further. As an aside, I’ve started giving a gentle de-clicker pass over my vox records as that seems to catch a few pops and cracks that I assume are A/D conversion artefacts. (Defaults but one pass only)

Tangentally, the other funny thing is back when I used to edit video, I knew how to repair shots and could do it efficiently. I knew what filter I needed for a shot or the right transition to use and how to set it just so. With audio I’m finding that there’s no one filter or edit macro I can use as the issues that do crop up seem to be different all the time. And it’s knowing which thing to use that takes most of my time; I fiddle to see if X does Y, or is it Z that does Y instead? Using the de-clicker, I fiddle with the settings until I don’t take the tops off 'T’s but can get rid of a little mid-word crack but I don’t know what the step size is or what it does or if my dense click threshold is too high. I just fiddle until it seems right.

Take this ripple I get sometimes, I know now that the Spectral Parameteric EQ helps it but I don’t know the best way to set it to rememdy any/all warbles that pop up, if I even can. Or indeed where to apply the effect; I just make a spectral selection enclosing the whitest bits and click OK. Nor WHY it happens in the first place so I can look to a fix there. The irony is that I edit audio like I do video; I check every cut and filter becasue I can hear things that other people can’t and perhaps that my trouble too. I played a clip with what I’d notice as a noise to someone else and it sounded fine to them, maybe I need to think it is sounds good, it’s good and worrry about big stuff.

Perhaps it is the Rode, I’ve been reading around that sometimes the casing can give some odd noises if the mesh is slightly loose (but the youtube genius also said the best way to fix was drill a hole into the mic and neglected to provide samples of the noise he was having) but untill I can catch the piggy back and see if another mic ‘fixes’ the issue it’s just a figure out as I go. Just missed out on a U87 clone on eB*y too.:frowning:

to that end, it took about six or so months to get a workflow that I feel reasonably comfortable with for audiobook/vox production: RX > import > low-pass > edit > gate* > ACX macro > mp3 export, if I’m doing an audiobook for example. But I still don’t know if that’s the best way to do it: it just happens that nothing submitted to any client so far has been rejected and I’ve got lots of broadcast experience so I know what I’m doing for reading/performance - but for me I don’t know if that’s the right way to do things, if you get me? And that ends up taking more time with audio work as I fiddle to see if there’s a better way to do something. I mean what IS the best way to edit an audiobook for instance? What if I applied the ACX macro at the start and then lo/pass/gate/edit. etc?

*tried dynamic mirror first but settled on gating

I find my own curiosity can sometimes be more of a burden than a help!

Here’s another few I just came across, listen to that ‘much’, it surprised even me!

I only fixed that by finding a ‘much’ from another sentence.

And my broadcast ears hear a ring on the word ‘humans’ in ‘humans make mistakes’ in this one, do you?

both raw WAV exports

Y’see I hear these little artefacts and then chase them for hours. I must try another mic when the opportuntiy arises.

Much” sounds like a digital belch, rather than a mechanical glitch.

IMO “Human” is a mechanical fault: there’s a click, then a short ring, as if the mic-diaphragm got stuck then freed itself …
'you Are only Human' before-after spectral edit in Audcaity.gif

good old conversion artefacts, must say I didn’t hear that at the time. But I guess I’m not hearing what the taplet hears, as I’m plugged into the interface.

Well there’s no way I’d fix that!

I do wonder then if the mic is duff. Could the other ripples and disortions also be mechanical? Something loose wollbling about to my deep, sonorous voice, maybe? I’ve kept the mic safely apart from the time the stand tipped and the whole shebang hit the floor, but that was a while ago… and thinking about it, the inital post was before that happened.

A poor workman blames his tools, I know, but I’ve found myself having to clean more audio with this mic than any others I’ve used in the past.

The mic component that includes the diaphragm, the capsule, is a replaceable unit.
They are expensive, £50-£100+, and delicate, so I would not attempt replacing one myself.

I actually meant using Audacity’s bells and whistles!

Cheaper to by a new mic then. But as I’m not in the mood for tearing the Rode down just yet, I don’t suppose there’s ways to test the mic I can do is there? I was thinking about using an oscillator on the phone to generate various tones and seeing if I see anything odd on the spectrograph. But I’m making it up as I go.

EDIT: they’re coming thick and fast now, does this unfortunately sound like a sticky diaphragm too?

EDIT 2: I just had a look at the NT1 and after removing from the mount, I noticed the end cap on the casing wasn’t as tight as it could be. Only a turn or so off finger tight, but I wonder if that might have been causng the vibration? Just finished this read so I’ll keeep an ear out next time I record.

ACX macro

Just to bring this around, is that the ACX Mastering Macro I wrote?

ACX-Mastering-Macro.txt (458 Bytes)
It has my name in the comment line. It has a rumble filter as the first step, so you may not need a second one in your process. Or if you do have two, one of them may not be doing anything.

This Macro suppresses the low pitch errors on many home microphones based on the broadcast and movie field recording filter, and guarantees RMS and Peak without sounding like it’s doing anything. It leaves noise up to you.

You have that robust male announcing voice and may have trouble with the high pass (rumble) filter. Listen carefully.

the NT1 has a metal popshield.

Can you post more info or a picture of the metal popshield. I know there is a common one that looks like a flat wafer.

That one works by simply not allowing large volumes of air through. I don’t know that it was ever accused of causing noises. It’s a lot more convenient than the large nylon tennis racket.


One more note. You can make up your own sound tests.

Without overloading anything, crumple up a newspaper in front of the microphone. That produces a remarkably even distribution of tones. (white-ish noise).

Tock two chopsticks or pencils together. That impulse sound will drive unstable errors (ringing, etc.) nuts.

And, by the way, you have young woman’s ears. I don’t hear any of those errors.


I noticed the end cap on the casing wasn’t as tight as it could be.

And a followup to that. Assuming the microphone is mounted on its floppy rubber-band mount. Gently thump the microphone. It should sound like thumping or better yet, almost nothing. If you get tinking, clanking or other oddball noises, then yes, there is something off.

A side note that you can have noises go up the microphone cable. Is it looped gently under the microphone connection point?