Need an audio clean done
 

Well, I am left to clean up a mess by a camera person who didn't have the volume up enough which gives me a loud buzz.

Is there anyone out there that clean this sample file, thus the whole file to a point that is worth saving?

Index of /temp/delete

Thanks in advance. If it ends up not being worth it, I'll probably just lay music over it.

Re: Need an audio clean done
 

Steven

I know it's beyond my ability to do it justice, but if you're using Sound Forge, under the FX Favorites menu, Sony, try the multi-band dynamics menu.
What it basically allows you to do is isolate a specific frequency ( in this case a hum), and filter it out. then you'd need to do a bunch of work with the volume and clarity of the audio to get it to a useable point.

I've used it in past to take feedback hiss from a cellphone out of audio. It's quite effective, but it takes a bit of fiddling around to find the frequency range so you can cull it out.

I'm sure some of the Pro's will have some other ideas to add
Hope this helps!
Wayne

Re: Need an audio clean done
 

Here's a try. Problem is (see noise chart) that the noise occurs over the very frequencies that the voices occupy. The noise is fairly easy to remove (noise reduction tool in Sony Sound Forge) but it also removes a lot of the voice content. What I did, and this is quick-and-dirty, so I'm sure it could be tweaked better: add 10 db the original file to get the levels up to where you can work with them. Apply 25 dB noise reduction, sampling from an area that has the buzz only. Apply equalization to try to boost the voice frequencies to bring back some clarity. Best wishes!

Re: Need an audio clean done
 

The good news: it's easy to get rid of the harmonic buzz using one of three techniques.
1.) a comb filter, which introduces a bit of echo,
2.) a series of sharp notch filters tuned to each of the harmonics, or
3.) some sort of adaptive NR based on a noise profile.
Of those, #2 is best because there's no echo (from #1) and no artifacts and "burbles" (from #3).

The bad news is: there are several other problems.

First, the repetitive impulse noise. There is no way to get rid of that. It's broad spectrum so any adaptive filtering will produce obvious artifacts in the desired audio. Its rep rate is pretty fast so it's hard to clean it with a noise gate... you can lower it slightly (and without artifacts) but you also lower the quietest voices. You can remove more of it with a "noise sample" approach but you will introduce a lot of artifacts. You're pretty much stuck with some impulse noise.

Second, there is some sort of bad intermod*. Listen to any of the voices, and you will hear a constant-frequency low-pitched tone that is modulated by the voice. If you watch it on a spectrum display, you'll see a peak at 150 Hz. You can dip this out somewhat, but it's still there if you listen closely.

(* I'm not sure what causes this IM. If I had to make a wild guess, I would say that the track as posted is not the original form... that a lot of LF has been rolled off from the original. In that case, a lot of 50 Hz, 100 Hz, and 150 Hz in the original, mixed with the desired audio, would cause this bad IM. Even rolling off the original LF hum, after the fact, still would leave the IM which is obvious at 150 Hz.)

Finally, the mics are much too far from the talent, and the room is fairly live. So even after reducing the noise to the point where it is "background," the speech intelligibility is still quite poor. Not useful for anything that I can imagine.

Sorry, I don't know of a magic "repetitive impulse filter" let alone a "bad mic technique filter" so I can't make this much better than my posted sample.

There are some (rather expensive) software packages designed for forensic use that might be helpful, but the result will probably sound very unrealistic.

Re: Need an audio clean done
 

This comes up a lot and most of the time the answer is no you can't get rid of the noise without effecting the subject too.

your energy is better spent figuring out how to avoid the same problem from happening again. that means a mic near the subject and the camera operator wearing head phones.

Re: Need an audio clean done
 

Thanks guys. I was hoping but oh well.

Re: Need an audio clean done
 

As Greg says:

"The bad news is: there are several other problems."

A nasty little problem indeed, broad spectrum noise everywhere and very 'roomy' as Greg mentioned. Had a play with it in Vegas and came up with the following, see attachment.

Re: Need an audio clean done
 

Addition to my previous post. Don't think it liked a 12MB .wav attachment. Smaller mp3 now attached. Doesn't sound the best but who knows... with music ovrlay it could get you out of trouble.

Re: Need an audio clean done
 

Christopher, this website likes only very tiny audio attachments. The "Manage Attachments" page lists the legal types and size limits. It doesn't seem to allow MP3s at all (very strange, since this is an audio forum!). Your best bet for compressed audio files seems to be WMA (also very strange... does Micro$oft own this website?). The 2.96MB limit on .zip files seems especially onerous, especially since it's legal to attach a 64.87MB .pdf file! (The pdf format is especially useless for any sort of media information, and this is a "media oriented" website.)

Better luck next time.

Re: Need an audio clean done
 

Mp3 is for pirates, you know!

(ducking!)

Andrew :-)

Re: Need an audio clean done
 

Well, beyond all the technicalities, I'd have a hard time thinking that this one could be saved even if we could remove all the extraneous noise - the voices are just too hard to hear and almost unintelligible with or without the noise. I definitely heard a question in Japanese and an answer in English, so we're dealing with different inherent sound patterns which I think would make it even harder to rescue it.

I think it's time for either the re-record filter or the drown-it-out-with-music filter.

Re: Need an audio clean done
 

Print it B&W, superimpose lots of grain and film dirt, and use title cards.

You must pay the rent.

I can't pay the rent.

You must pay the rent.

I can't pay the rent...

Loop ad infinitum.

-----

Seriously, one has to wonder whether this was some sort of "stealth" recording, unknown to the principals involved. The mic was surely nowhere near where it should have been.

Re: Need an audio clean done
 

[QUOTE=Greg Miller;1641846]Christopher, this website likes only very tiny audio attachments. The "Manage Attachments" page lists the legal types and size limits. It doesn't seem to allow MP3s at all (very strange, since this is an audio forum!). Your best bet for compressed audio files seems to be WMA (also very strange... does Micro$oft own this website?).

I tried a WMA file but it doesn't hold up as well as a WAV so am trying again with just the middle 36 secs where most of the dialogue was. Hope this attatchment gets thru!

Re: Need an audio clean done
 

Less noise, but, of course, at the expense of terrible artifacts. I can understand very few words in the speech... it's extremely robotic. That's the trouble with using sample-based cleaning with a broadband noise.

Re: Need an audio clean done
 

I'd have to say that the original clip has more harmonics with significant energy marching into the frequency stratosphere than I can remember seeing in a long time I'm really at a loss to figure out how this got to be so bad. Sort of a perfect storm of noise.

Are you sure someone wasn't trying to jam the signal? Was it recorded at the base of a broadcast tower or next to a radar installation - or were the mics hidden in a microwave oven:-)

Re: Need an audio clean done
 

Jim, the buzz consists of numerous exact harmonics of 300 Hz, first noticeable at 1,200 Hz and running up through 12,000 Hz. So as I said earlier, the exact 300 Hz spacing makes it easy to remove the harmonics with a bunch of notch filters; and that does not create artifacts, the way a "noise sample" approach does.

There must have been some sort of very exact 300 Hz signal present in the equipment or nearby. I do not think it's related to a dimmer or other power line system, because there would be other harmonics of 50 Hz in there. Offhand I can't think of any equipment I've worked with that is running a precise 300 Hz clock signal... can you?

The repetitive impulse noise might be crosstalk from a display somewhere. Some of the early MP3 recorders had this problem, because of insufficient shielding, or ground loops, between the input stages and the display circuitry. The cheap "Wristwatch Spy Recorders" also produce noise like this... maybe this track was recorded on one of those (still not in the right location).

Recently, I heard this sort of impulse noise when I was testing a mic made by "Sound Professionals." I discovered that if the mic wire was anywhere near the display on my DR-07 or DR-03, it would pick up noise like that. The source of the noise is apparently the strobe signal from the display. The reason that mic picked it up is because "Sound Professionals" uses unshielded headphone wires on many of their microphones! Appalling! When I tried the same test with a "real" microphone, using shielded cable, of course the noise was gone.

Re: Need an audio clean done
 

Hi Greg

Yes - that's the thing that's bothering me - I can't think of anything that would be at exactly 300Hz.

I would also tend to think most/all of the "trash" would not have been present if proper cabling had been used.

However, even absent the noise, I think this would be hard to salvage. Wrong/improperly placed mics for sure. Poor recording space.

Re: Need an audio clean done
 

Hi Jim,

Good point, and I really didn't think about that. The highest audio was only about -10dB below FS, so the problem isn't caused by low mic gain as the OP suggested. In fact if recording gain had been 10dB higher, the noise would probably have been 10dB higher, as well.

In fact, maybe the recording gain was too high, and that's what caused the noise level to be so high. Clearly nobody in this clip is anywhere near being "on mic" so maybe that caused the camera op to set the gain too high, increasing the noise level, too.

I sure would like to know the source of the 300Hz pulse. IIRC the old rotary VCRs had a sync pulse that was 4X the nominal frame rate; but I can't imagine what would be using 300Hz these days. And would the freq. be higher or lower on the "defrost" setting?

Re: Need an audio clean done
 

Yeah, this one has me stumped - if it were a motor arcing it would have to be running at 18k RPM - I even Googled around looking for 300Hz.

Whatever it is, it's well regulated and consistent - wonder if it could be the head motor if the camera was using tape - not sure how fast that spins - I think 18k might be too high.

The other surprising thing (to me at least) was how high in the harmonic range there was significant energy. I think most hum has pretty low energy in the upper harmonics.

'Tis a mystery - MUST have been the defrost cycle.

I'm also thinking that the gain must have been cranked up about as far as it would go.

The other thing that has me scratching what's left of my hair is what kind of group this was. I heard a few different accents on the English speech, something completely unintelligible, and I clearly heard somebody speaking Japanese.

Re: Need an audio clean done
 

I very much doubt a motor arcing. First of all, the arcing would not be constant, it would be continuously changing. So even if the fundamental frequency was steady, the level of the various harmonics would be up and down randomly. But as I think about it, I doubt that the fundamental would be that steady, because of minor dimensional variations in the size of the commutator segments. Nah, not an arcing motor.

It's not hum based. "Pure" hum would be just the fundamental. You get harmonics on power line "hum" because of changing imbalance on the 3-phase distribution system, as well as higher harmonics from switched loads like dimmers, variable speed motors, etc. These tend to be odd-order harmonics, so they'd be 300, 900, 1500, etc. On the other hand, if I recall correctly, a triangle wave or a narrow pulse contains "all" harmonics... "all" meaning within the bandwidth of the system in question. So apparently something in the recording chain rolls off up around 12kHz. (Actually, I'm a little unclear about why the first 3 harmonics -- 300, 600, 900 -- seem to be missing. But depending on how the noise was coupled into the recording chain, I guess the coupling at lower frequencies might be much more lossy than coupling at higher freqs.)

Hah! I also Googled things like "300 Hz sync" and "300 Hz clock" but found nothing that seemed even vaguely relevant. Interestingly, I googled "300 Hz sync pulse" about 2 minutes after my initial reply here, and this thread came up at the first hit! How do they do that?????

It's much too fast for vertical sweep, and too slow for horizontal sweep, on a typical display. Surely nobody would use a 300Hz inverter to step up battery voltage to 48v phantom voltage... they'd want to use something far above the audio range. So I keep coming back to something like the pulse from the sync generator on a motor, or a reference pulse for a motor somewhere.

I hope the OP will fess up and tell us what sort of equipment was used to create this recording, so we can do a little more research. In fact complete silence from the OP makes me wonder whether he intentionally created this mix just to pull our legs. (OK, so I always was a sucker for conspiracy theories.)

Otherwise, my hunch is that this was recorded in a 3-room apartment, with an English soap playing on a TV in one room, a Japanese soap playing on a TV in the second room, and a "Spy Watch" recorder hidden under a pillow in the third room.

Re: Need an audio clean done
 

Damn - makes me feel like Sherlock Ohms on a bad hair day.

Just can't come up with anything remotely plausible to explain this mixed salad of noise.

Maybe it's an international student lounge set up inside a giant industrial microwave oven. And they're all being defrosted.

By the way, came up with an interesting site whilst googling around. (I remember using 2 inch tapes a million years ago, although not for video - they were for radar signature analysis and the reel was about a meter in diameter and mounted on the rather enormous reel to reel drive with a little forklift.)

Scan