Removing Hiss

When I first saw the Post Title, I thought to myself -- I'm tired of these motherfuckin' snakes on this motherfuckin' plane! How do I get rid of the Hiss!?!?

Seriously, the best answer I got is to get with someone who knows more about sound filters and such. Send him/her a mp3 of the audio, let 'em clean it up, then get it back. I don't know if that's the advice you were looking for, but it's the best I got.

Poke

Use Audacity ... it works great, and it's free.

You simply select a region of your clip that is just noise, then select the region to be fixed, and Audacity uses the noise signature to remove the noise from the entire selection. It's amazing.

Yes, for a free app, Audacity has tremendous tools. Link

Poke

On the EQ its usually in the 16k-20k range, but could go as low as 12k depending on the mic/ambient. an easy way to experiment is to open the file in any media player, and open the eq, which is usually 20 band, sometimes 10 or 15. Its always in the highest # sliders. And to be honest, I think this is a step of sweetening we should all be using for our dialogue and ambience tracks, gives you a chance to set some real soft rolloff and great seperationg between your people and their locations.

White noise can cross the entire spectrum, from subsonic to hypersonic. The equalizer approach is the only hope when working live, but I've found it to be less effective than the noise filter approach that Audacity uses, when working in post.

I just recently had a terrible noise from a wireless setup that I eventually narrowed down to a noisy power supply on the receiver. I didn't need stereo audio for the gig, so I used a wired mic on one channel and the noisy wireless on the other. When I got back to the studio, I seriously considered just tossing the noisy channel and going mono, but there were some things that the wireless mic picked up that weren't as clear on the wired mic. The noise was terrible, and it defied my attempts at filtering it in Apple's Soundtrack application (bandpass filters, 30 band equalizer, etc.). I decided to export the audio to AIFF, open it in Audacity, and give that a try. I had used Audacity for the standard hiss before, but nothing like this. Much to my amazement, I was able to use the audio track, and it actually came out very clean. I panned the two tracks so they overlapped about 30% and the final audio was great.

Of course, it's always better to get clean audio from the start, but my life isn't like that.

Sorry Wideshot, you get one thumbs up for the sweetening tip, and a thumbs down for the best noise removal!

oakstreetphotovideo said:

White noise can cross the entire spectrum, from subsonic to hypersonic. The equalizer approach is the only hope when working live, but I've found it to be less effective than the noise filter approach that Audacity uses, when working in post.

I just recently had a terrible noise from a wireless setup that I eventually narrowed down to a noisy power supply on the receiver. I didn't need stereo audio for the gig, so I used a wired mic on one channel and the noisy wireless on the other. When I got back to the studio, I seriously considered just tossing the noisy channel and going mono, but there were some things that the wireless mic picked up that weren't as clear on the wired mic. The noise was terrible, and it defied my attempts at filtering it in Apple's Soundtrack application (bandpass filters, 30 band equalizer, etc.). I decided to export the audio to AIFF, open it in Audacity, and give that a try. I had used Audacity for the standard hiss before, but nothing like this. Much to my amazement, I was able to use the audio track, and it actually came out very clean. I panned the two tracks so they overlapped about 30% and the final audio was great.

Of course, it's always better to get clean audio from the start, but my life isn't like that.

Sorry Wideshot, you get one thumbs up for the sweetening tip, and a thumbs down for the best noise removal!

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LOL thanks for the backhanded compliment... but I think we are talking about two different things here maybe - 1) typical high frequency hiss found in recordings with high gain or low directional pickup, which can generally be cleaned off fairly effectively with just eq faders, and then there is 2) noise, static, AC crossover hum, 60hz camera hum, etc... all of which are best to be removed with filters, programs like audacity or SoundSoap or even intense filtering/eq adjusting on several different bands. As you said, something like static or noise can be all over the spectrum! Thank god for programs like audacity or SoundSoap though, they make cleaning audio much easier.

Ok, Wideshot, you win this battle ... but this isn't over ...

Seriously, though ... you are absolutely correct on all counts, and I hate that! The Audacity/SoundSoap route is a catchall, though ... for when you don't know what kind of noise someone might be up against.

(a sloshing sound can be heard, as Doug descends back into the dark swamp)

"I'll be back" (blub, blub, blub)

(A deafening silence follows, as onlookers ponder how long it will be, before he returns to sow terror in the hearts of indietalk members everywhere)

I bet it'll be just when we think it's safe to go back into the swamp.

Poke

Thanks Guys for the information

I'm going to try to clean it up in Soundtrack Pro using the following technique I found pooching around the net

Do you have Soundtrack Pro there is an awesome feature in it that will take out the hiss. You have to be really careful with it some time it will make your audio sound like your talent is under water.

So you have to use it in small increments.

If you have soundtrack open what you would do is import your clip and then select some of the hiss.
Then select process "Set Noise Print"
Then select all of the audio with the hiss in it and then go to process "Reduce Noise"
Turn on the box that says "Noise only" adjust the slider till you can barely hear your talents voice and then back it off slightly. Listen carefully and back it off a hair more.

Click apply give it a minute or 2 to do its thing and Hiss is gone.

If its still there resample and repeat don't over do it it will ruin your audio. Less is more. Very Important do make sure you do this on a copy of your media NEVER the original.

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If that doesn't work I'm going to use Audacity

And I'm also going to look at the 16 - 20K EQ sweetening -- these are all great tips

I'll keep you posted.

I would be very interested to hear how it goes with Soundtrack Pro. If you get chance to give us an update I'd love to hear it.

Hi All

Well, I had a play with Audacity yesterday and although it removes the hiss, it puts a high frequency flanging sound into the audio -- which IMO is worse than the hiss. (this was even with the remove at it's lowest setting -- so I don't think there's enough overall sensitivity in Audacity for this kind of work)

So, today I'm going to try the same process in Soundtrack Pro -- I was going to do that yesterday, but ran into some time issues and ended up cutting some other footage instead.

Using the Graphic EQ to cut at 16000hz was a stroke of genius by the way -- it makes a considerable difference and is something that I'm going to do as a matter of course from now on.

The other development is that the hiss is actually mainly on the right channel -- this is interesting because I've got a mono mic going into the left channel, but when the mini jack goes into the audio input it places it on both channels. So there shouldn't be a problem -- but there is for some reason.

I've a friend who uses the Sony VX2000 (I'm using the VX9000) and he's had the same problem. -- So today I'm going to look at the manual, play with the set up and see if I can eliminate this problem from future recordings.

If it's not a switching problem I think I'm going to put a tail between the mic and the Beachtek unit and feed the audio in directly to both channels. But, I'll keep you posted.

LATER:

So, I've done some more research and this hiss problem is built into the Sony VX range -- it's a pre-amp chip problem which adds a low level hiss on ALL audio (damn it) -- so my basic errors just highlighted the weakness in the camera's electronics.

One of the things that I did that compounded the problem was to take the audio out of the AGC (automatic gain control) and switch to manual -- In any other camera this would result in better audio -- but in the VX range it appears to do the opposite.

Anyhow, apparently the BBC used to modify VX2000's to fix this problem -- I'm going to see if they still do this and get my camera modified.

EVEN LATER:

Damn it! --- I've only got Soundtrack 1.2, not Soundtrack Pro -- this is getting tedious now -- looks like I'm going to have to go down the Sound Soap route. (Cheaper than an upgrade)

There is a hiss removal tool in Soundtrack, but I'm going to need a quick tuturial from someone more up to speed with the software to get my head round it. I'm got a mate who is up to speed on that, and who ironically has had the same problem with his VX2000.

This is looking like a next week problem now.

However, good news is I'm learning massive amounts about both my camera's performance limits and post production sound in the process -- so, not a complete loss.

If you can have the preamp in the camera modified that would be ideal. In the past, I've had to deal with some pretty poor / noisy mic preamps, noisy wiring from cheap mic, etc. I've found that noisy amps make a lot less noise if the gain is set below 50%, and noisy wiring can be saved, if the signal on the wire is preamplified so the signal gets well above the noise floor. I fix the two problems in much the same way. Although I hate extra batteries, or extra crap to drag along on remotes, where it's practical, a clean microphone preamp, as close as possible to the microphone can provide the necessary boost.

The catch is that you have to make your own preamps, unless you want to spend a lot of money. Cheap preamps are noisy, and professional ones are expensive. A very clean, homemade preamp is not as complicated as you might think, and it would allow you to keep the gain low on your camera, or even use a line level input.

I'm really sorry to hear that Audacity couldn't clean your audio. I've only had to use it 3 times, but every time it has performed flawlessly for me.

p.s. Was there a reason you weren't using your Beachtek on the shoot in question? I would have expected the Beachtek to provide clean, preamplified mic/line level output to the camera. Just wondering what kind of setup you were using that had a 1/8 inch mono plug.

I'm really sorry to hear that Audacity couldn't clean your audio. I've only had to use it 3 times, but every time it has performed flawlessly for me.

p.s. Was there a reason you weren't using your Beachtek on the shoot in question? I would have expected the Beachtek to provide clean, preamplified mic/line level output to the camera. Just wondering what kind of setup you were using that had a 1/8 inch mono plug.

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Thanks for the additional info.

I was using the Beachtek unit and if I'd boosted the signal at that end and cut the levels at the camera the hiss would have been a lot less (but as I said, I lost concentration on the shoot and made some basic errors, which were then compounded by idiosyncrasies of the camera)

From the research I've done, the only way to solve this problem is to have the camera modified so that the pre-amp chip is bypassed (which is a hardware alteration). It's a design flaw in the what is otherwise a stunningly good camera, which is true to all the Sony VX range and the PD150.

As to the set up -- Well the VX series doesn't have XLR in -- it's a stereo mini jack input for audio (lame I know, but Sony really lost the plot on audio with the VX series) -- the set up was an Audio Technica AT897 on mic stand -- XLR into Beachtek DXA-2S -- stereo mini jack into audio input.

The AT897 is a mono mic and went into the left channel of the Beachtek, but obviously that goes onto both channels of the audio when it hits the camera -- unless you have a separate mic going into the right channel.

The problem here, however, wasn't about what went into the camera (other than me setting the input levels too low -18db, rather -12db) it's was mainly about the VX series pre-amp problems.

As to Audacity -- well, it could be that I didn't use the software properly -- being as it was the first time I'd used it -- that's entirely possible. -- But, having talked to a few VX owners now, they all say that the noise gate software in Soundtrack Pro is the way to go on this problem.

However, I would be interested in hearing from any Sony VX users about how they get clean sound.

PS -- A tutorial on DIY pre-amp production would be very, very welcome

PS -- A tutorial on DIY pre-amp production would be very, very welcome

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In a couple of months, when my schedule will hopefully be more manageable, it might be fun to go through the construction of a simple mic level amp, step by step, on video. I can already imagine that people will hate me by the time I'm finished, because I take for granted the tools, supplies, and parts that one accumulates over years of basement electronics hacking. I also don't know what would be most useful to people. One of my recent challenges was to build an inexpensive but 100% clean amp that would take a balanced mic input and output to a line-level, with an RCA plug, so I could use any, consumer level, stereo recorder (e.g. cassette or minidisc recorder), which is about 1/3 the price of a professional recording system with balanced inputs. You can buy a decent minidisc recorder at a pawn shop or on E-bay for a song, these days, but it probably won't have any mic level input.

So, the trouble with making a $15 circuit to save a couple hundred bucks, is that you really need to know exactly where the circuit will be used; what will plug into it, the gain that is required, if it needs to provide phantom power to a powered mic, and what kind of output you need from it. I keep parts on hand for virtually everything I can think of, because the parts are so cheap (often a complete, low-noise, audio-frequency pre-amp on an integrated circuit will cost about $0.35). You might need a couple of those, a handful of $0.05 resistors, a couple of capacitors, and the proper plugs/jacks. An XLR jack is about $4.00. It hardly seems fair.

Since the IC (integrated circuits) are designed specifically for low-noise, pre-amp applications, their spec sheets often include the circuit diagrams for a complete amplifier (sans the power supply and external packaging). Probably the biggest hurdle for someone new to building solid state gadgets would be soldering technique, and circuit board design/fabrication. If you're familiar with soldering heat-sensitive chips, and etching circuit boards, the rest is easy. Learning those two things, and buying the supplies and tools could be a hit that some people would rather not take.

Returning to the problem of specifically what to build in a tutorial; it seems that the balanced circuits are the ones that are priced the most outrageously, so I guess I'd stick to the balanced to unbalanced and unbalanced to balanced conversion, impedence matching, and in-line amps that would extend the usable wire length for balanced and unbalanced equipment. Also, a pre-amp on a dynamic microphone, that is installed very close to the mic, can enable more amplification, and therefore, better pickup from the dynamic mic.

Those are just my thoughts. I'd welcome any insights into common problems people have run into that might be solved by an inexpensive gadget. I won't be doing a tutorial any time soon, because I'm just too busy, but it would be nice to know what to do it on, when I get time.

Hi Guys

Well, I've managed to solve the problem and in the end it was massively easy -- once I knew what I was doing.

I'd just like to send a big THANKS to Freezer who put me on the right track.

Basically, what I needed to do was apply two filters to the track -- firstly a Low Pass filter which in this case needed to be set at about 4000hz and then a Parametric Equaliser which I finessed until it cut the rest of the hiss.

The whole process only took two minutes and gave none of the nasty upper frequency phasing sounds produced by the audio scrubbing software.

The sound is marginally thinner than I'd like, but that's because it's off mic and in real terms I can live with that.

In terms of the built in problems with the VX range of cameras, I've gathered some more information as well.

Basically the BBC used to offer a modification that by-passed the offending pre-amp -- but the department that did that no longer offers the service. However, the trick to minimising the hiss is put as much signal into the unit as you can and reduce the camera input levels -- this means less pre-amp effect. If you do this the hiss is barely present -- however, I still think some basic filtering would be necessary if you were thinking about feature production.

In other words the VX range just need damn near perfect recording technique at source -- it's not a forgiving camera on the audio side -- and I'm seriously considering recording the audio separately for my next drama project.

The best piece of information I got with this problems was "go buy Jay Rose - Audio Post Production for DV"

I got all the information I needed to fix the problem in twenty minutes skim reading. I'm now working my way through the rest of the book.

Glad I could help by just pointing into the right direction