Hello All -

I am currently working a production, and am a bit puzzled by some hiss I'm getting with my audio equipment. I'm using a Zoom H4N, with new batteries, standard XLR cable, and a Sennheiser MKH416P48 (using phantom power from the Zoom). If you listen to the attached file, turn it up, you'll hear quite a hiss, and even the faintest high pitched ... something? Not entirely sure what may have caused it (the pitch thing), but I'm guessing that we have the gain too high on the Zoom, which is causing the hiss. Or maybe it's some sort of interference caused by our light kits, which were situated fairly close to the talent. I'm not an audio guy, but I'd love to try and clean this up a bit myself. I don't have access to a post house, which means I do most of my own editing (both audio and video). I'm using the Adobe CS5 suite, and have Soundbooth. I'm not entirely sure what to do to clean up that hiss without making some of the audio sound hollow. Premier Pro has an audio effect that reduces noise, but as I push it passed 4dB, the audio starts sound hollow. Any and all recommendations would be great!

http://www.burntbridgefilms.com/MONO-056.wav

Sorry, I don't see your "attached file."

That was actually my bad. I tried to attach it and it was much larger than the forum allows to attach, so I just uploaded it to my server and posted the link.

I'm hearing acoustical borne background noise. And some intermittent static? A spectrum analysis indicates a slight bump around 11k-12kHz.
Are you hearing this though the recorder's noisy headphone amp?

Unfortunately, I wasn't the one recording, but I've since fired it up myself and I do hear the hiss. Just not the high pitched ... whatever we're calling it. I do hear it, and hopefully we can avoid that tonight during out shoot. But if it does happen again, I'd love to do what I can to remove it.

A hear and see pretty much the same thing that Rick does. There's a lot of room rumble, but that's LF. That is actually a lot more annoying to me than the hiss. There is also some airborne hf noise, a lot of little clicks and ticks, but they sound as if they're actual recorded sounds from the set/room. There is a tiny peak in the noise level, around 12 kHz, but I don't think that's significant to what you hear.

There is no buzz, which would be harmonically related to power line frequency. So I don't think there's any noise from your lights or dimmers.

There is an odd little patch of HF noise, starting around 1:42, right after the word, "Man" and up to the phrase, "I don't know." Without seeing the video, it's hard to speculate about this, but my first guess would be that it's noise of moving clothing, or some object moving on the set. I can't imagine anything happening electronically to cause that particular bit of extra noise.

As to the amount and source of hiss, that's a toss-up. I'd want to hear the same mic, same recorder, same gain settings, but all recorded in a completely quiet location (none of the rumble and other airborne noise that I hear in this track). Then we could ascertain how loud the electronic hiss is.

And then if you'd unplug the mic, and replace it with a 200 ohm terminating resistor, and record some of that track at the exact same gain level, we could speculate about how much hiss is coming from the mic, and how much is coming from the recorder.

I made a Soundbooth tutorial that will help you reduce the noise without (hopefully) degrading the signal. Hope it works for you.
YouTube - Advanced Noise Reduction in Adobe Soundbooth (http://www.youtube.com/watch?v=tMC1OJl2v_k)

The hiss is probably the Zoom preamps. I actually didn't find it bad at all in your example, the room tone covered it up mostly. Perhaps you could try a mixer with better preamps, before going into the zoom?

I'm going to make a guess here - the clap at 8secs - look carefully - the top and bottom is clipped, yet the level of the rest is pretty low. I wonder if all that's happened is that the recorded audio is just not hot enough, so gain applied afterwards to lift it has brought up the noise floor? the average level is around -9dB ish? The more distant speaker is even less. Just to experiment, I took a few of the dialogue 'chunks' and raised their level - then adjusted the listening level down to my usual level, and the noise floor dropped quite nicely in between the dialogue - suggesting that it's a dynamic range problem. I'd be tempted to make the whole thing hotter when recording and maybe just have a limiter to prevent it going over the top

Now that I've had the chance to look at some of the other audio that I've recorded, I found that there was a similar HF distortion in all the files created while shooting at that location. One thing I noticed is that about 3/4 of the way through the clip, (looking at the spectrum analysis), you can see it drop in pitch, which I find really strange. The slope of the decline is pretty consistent. Taking this into consideration, and that the Zoom was most likely set rather low, I'm guessing the batteries were starting to give out. The subsequent recording sessions we had produced no similar distortion, nor did it occur beforehand. I was rather certain that we changed the batteries before we began that day, but it's the only thing that I think I can come up with that caused this problem. Mostly because I've not been able to reproduce it again in my home. Either way, I was able to select the frequency, take a noise print, and clean it out.

Perhaps the best way to avoid this is, as you said, use a stand alone mixer. I've used on in the past, but being just barely above novice, I find it just adds more places where I can screw things up.

Cheers to you guys. You're experience and knowledge is invaluable.

I'm always uncomfortable using it for extended periods on batteries. It really could use 4AA instead of 2. The battery life is even shorter when providing phantom power. If the XLR cable is long (lets say 50 ft) between the mic and H4N thats also another area that could induce noise plus makes it harder to supply power to the mic.

Our XLR is in fact 50 ft. I'm wondering if it might be a better idea to just find an outlet and power this off the wall socket. Obviously can't be done everywhere, but could be done in shoots that have the extra socket.

Course, gotta be careful in some instances. We did trip the breaker on accident on our last shoot. Would have to keep that in mind, but I can't imagine the Zoom draw that much power.

That could be your problem. I know that using anything over about 20' to 25' cables can cause the problem you're talking about. At least, that's what I've read time and time again.

A long cable won't add hiss. It will make the signal more prone to interference. It will also roll off the highs if the cable is exceptionally long. It won't be a source of hiss though.