What, Exactly IS hiss?

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Doctor Varney

Cave dwelling Luddite
I realise this sounds like a bit of a dumb question. Why, it's that "Ssssss" noise on your audio of course!
But what is the cause? Hum, in my case, is usually caused by some equipment which is causing vibration, I suppose. So what is hiss?

Edit:
Seems obvious for me to assume, it may come from using mediocre equipment in many cases - but what exactly would you say is the main factor(s) in such equipment that might be generating this sort of noise?

Thanks in advance

Dr. V
 
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A lot of the "hiss" we hear nowadays is sidebands and harmonics of EM signals flying through the air. Any one of these signals might come up as a whine or buzz, but when combined with all the other signals randomly bombarding a circuit any any given time it sounds like broadband noise.

Much of it is also "thermal noise" - literally the sound of the atoms in the conductor bouncing or vibrating around and taking their swirling field of electrons with them. It's the sound of brownian motion. Everything has this going on, but large resistors in series with the signal path are usually the worst contributors in audio circuits.

Course then there's "tape hiss" which is the sound of randomly oriented magnetic particles on the tape itself. Those of us who have abandoned that legacy format have said "goodbye and good riddance" to that particular waterfall...

...But in its place we get dither noise, which is (or should be) added to a digital signal any time a change in bit-depth happens. It's usually nowhere near as loud as any of the others, but it gets added at various stages in the process, and can sometimes end up adding up to a noticeable amount.
 
Very informative, ashcat_It. Thank you very much.
 
there's no single Error...

signal path, electricity current, bad wires, bad connectors, bad plugs, under or over powered components.... all can cause unwanted noise and the science behind them are all different
 
Thanks, CMB.

So - is there anyone here who can say for definite there's no hiss or extra background noise of any description on their recordings (their quieter recordings).

a) If no, do you use software to remove it? Is noise removal an accepted part of your workflow?

b) If yes, then presumably your environment is good - but what would you say is your optimum combination of mic and pre-amping structure used for recording quieter material?

Since I came straight into home recording, with zero experience of the professional world, I'm trying to get a sense of what can be reasonably expected when setting up your own little studio.

I appreciate if the question sounds a bit like "How long's a piece of string" - but generally speaking - I mean, (vintage tape issues aside) do professional engineers also have to deal with noise - however slight? Or is it more the mark of an amateur?

I also appreciate that you might say a loud distorted guitar wouldn't matter so much - and then loud passages of music can hide any hiss in the quieter tracks. I'm more interested in what sort of acceptable benchmark/ threshold you would have for noise/ hiss, etc... and how you personally deal with it.

Cheers

Dr. V
 
Doctor Varney said:
Cheers! Very handy equation, that. I will have to note it down, for future reference...
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For years, I had to endure a colleague, when he wanted to be awkward and not think through an answer, saying "how long is a piece of string ?". Then years later, I said the same thing to this 11 year old called Ben. It was, to give credit where due, him who said "Twice as long as half". Apart from me, he's the only person I've ever heard actually answer the question and I got it from him. I was so impressed that I used the question and answer in the lyric of a song {"Varuni's bag"}.
I never did get to say it to my former colleague. By the time I heard it from Ben, we'd 'lost' {more appropriately 'never even entertained the falseness of maintaining'} contact.
 
professional mixes do not have noise (or at least not audible noise) ... to follow my first comment... find where the noise source comes from and fix it... could be a cable, could be an input... could be dirty power... could be a lot of factors.
 
Oh horse hockey! Professional recordings most certainly do have have noise! They're just better at hiding it. Masking, muting, gating, filtering, or whatever it takes. Every damn thing makes noise and there's absolutely no way around it in the really real world. Even with completely ITB, totally synthetic, computer generated music you'll still have dither/denormal noise to deal with.

Yes, pro gear - installed properly and correctly in a generally low noise environment - might be even a lot better for S/N than a budget setup in a basement with flourescent lights, a furnace, and a chest freezer, but there is no place in the known universe completely free of noise.

 
Hiss is probably the last thing you should worry about. I think hiss is pretty actually.
 
Hissing isn't really the killer if your music isn't all that great! Most people don't give a damn about hissing noises.
 
DarrenVocal said:
Hissing isn't really the killer if your music isn't all that great! Most people don't give a damn about hissing noises.
Click to expand...

True, and in some cases the more hiss the better! :D
For example, I'd much rather listen to hiss instead of _________
 
I think Doc Varney is doing voice over and hiss is his number enemy. No music to blotch over the noise, it's either speech or nothing.

I don't listen to spoken material much, but the little I had did not have any hiss. So, that makes me think if you have any kind of unwanted noise in your recordings, you need to find the source and eliminate it.

Spoken word and musical recordings are not the same thing.

I'll go out on a limb and say your hiss is one of two things: 1) environment - You need a GREAT place to record spoken word; 2) Poor gain staging - you don't have your knobs dialed in properly.
 
Doctor Varney said:
b) If yes, then presumably your environment is good - but what would you say is your optimum combination of mic and pre-amping structure used for recording quieter material?
Click to expand...

Oh now, see?? You already knew what is important.

a) If no, do you use software to remove it? Is noise removal an accepted part of your workflow?
Click to expand...


This is only to fix a problem after the fact. You should be addressing it before the fact. You shouldn't be using software to remove noise. Find the source. If you use software, you'll have other artifacts that won't sound good compared to pro level stuff.
 
Chili said:
I'll go out on a limb and say your hiss is one of two things: 1) environment - You need a GREAT place to record spoken word; 2) Poor gain staging - you don't have your knobs dialed in properly.
Click to expand...

Maybe Dr V could describe the specific set-up, and post a sample of a problematic recording.

An inherently noisy and/or insensitive mic would not help.
 
Chili said:
I think Doc Varney is doing voice over and hiss is his number enemy. No music to blotch over the noise, it's either speech or nothing.

I don't listen to spoken material much, but the little I had did not have any hiss. So, that makes me think if you have any kind of unwanted noise in your recordings, you need to find the source and eliminate it.

Spoken word and musical recordings are not the same thing.

I'll go out on a limb and say your hiss is one of two things: 1) environment - You need a GREAT place to record spoken word; 2) Poor gain staging - you don't have your knobs dialed in properly.
Click to expand...

Bang on, chap! You've dialed directly into my situation - which shows you actually read my post. :thumbs up:

Regards

Dr. V
 
Anyone claiming to have a piece of electronic equipment without any noise is telling you a lie. Even the universe itself has a background hiss that you can hear with the right detectors.

Any chain of electronic gear (in this case microphone, pre amp, A to D converter) is going to leave you with the sum of the noise in each item.

What this means is that you're not trying to eliminate noise, just keep the ratio of your voice to the background noise at a point where the noise isn't audible in any normal listening condition. There's noise in every recording I've ever done--but, with care, it's at a level where you have to zoom in on the waveform in you DAW to find it. In my home studio it typically sits at around -85dB.

How do you achieve an acceptable signal to noise? There are a bunch of things.

First, almost any condenser mic will have a superior noise figure to any dynamic mic.

Second, be careful in your choice of pre amp. The process of adding gain (the function of a pre amp) also adds noise. A good pre amp adds less than a poor one. Use your decent pre amp with a condenser mic (which'll have a higher output) and it's quieter again.

Third (really following on from the second item) if you have any other bits of gear in the chain (mixers, outboard effects) be careful of your gain staging. You want a nice even flow of gain through the system rather than turning it up too loud in one place, then reducing it at the next stage, then up again. Keep it even.

Fourth, watch your monitoring. Monitoring involves an amp again. It doesn't affect your actual recording but, turned up to high, can fool you into thinking you have more hiss than you really do.

Now, be aware that for all this I'm talking about ELECTRONIC noise (hiss). Room noise is something else again and the causes and cures are very different. For music, you want a nice sounding room. For spoken word you want a dead sounding room. A folding frame (PCC pipe works well) with a layer or two of duvets or moving blankets placed behind you helps hugely. Another layer of soft stuff on the wall opposite you (the one you're facing) pretty much finishes the job. Keep both softies a few feet away from you--you don't want to be in a closed box because it sounds, well, boxy.

Frankly, the quality of modern gear is such that, in terms of electronic noise, any microphone/interface combination above the absolute bottom feeders should give you an S/N ratio somewhere between 80 and 90 dB. As for room noise, that's up to your skill with duvets.
 
Bobbsy said:
Anyone claiming to have a piece of electronic equipment without any noise is telling you a lie. Even the universe itself has a background hiss that you can hear with the right detectors.

Any chain of electronic gear (in this case microphone, pre amp, A to D converter) is going to leave you with the sum of the noise in each item.

What this means is that you're not trying to eliminate noise, just keep the ratio of your voice to the background noise at a point where the noise isn't audible in any normal listening condition. There's noise in every recording I've ever done--but, with care, it's at a level where you have to zoom in on the waveform in you DAW to find it. In my home studio it typically sits at around -85dB.

How do you achieve an acceptable signal to noise? There are a bunch of things.

First, almost any condenser mic will have a superior noise figure to any dynamic mic.

Second, be careful in your choice of pre amp. The process of adding gain (the function of a pre amp) also adds noise. A good pre amp adds less than a poor one. Use your decent pre amp with a condenser mic (which'll have a higher output) and it's quieter again.

Third (really following on from the second item) if you have any other bits of gear in the chain (mixers, outboard effects) be careful of your gain staging. You want a nice even flow of gain through the system rather than turning it up too loud in one place, then reducing it at the next stage, then up again. Keep it even.

Fourth, watch your monitoring. Monitoring involves an amp again. It doesn't affect your actual recording but, turned up to high, can fool you into thinking you have more hiss than you really do.

Now, be aware that for all this I'm talking about ELECTRONIC noise (hiss). Room noise is something else again and the causes and cures are very different. For music, you want a nice sounding room. For spoken word you want a dead sounding room. A folding frame (PCC pipe works well) with a layer or two of duvets or moving blankets placed behind you helps hugely. Another layer of soft stuff on the wall opposite you (the one you're facing) pretty much finishes the job. Keep both softies a few feet away from you--you don't want to be in a closed box because it sounds, well, boxy.

Frankly, the quality of modern gear is such that, in terms of electronic noise, any microphone/interface combination above the absolute bottom feeders should give you an S/N ratio somewhere between 80 and 90 dB. As for room noise, that's up to your skill with duvets.
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All good points, B. I'm dealing with a small mixer now and I get a good bit of hiss from my pre's. With nothing on the board by my phones, I can hear hiss with a low gain and moderate levels from a preamp'd channel. I think I'll be swapping the unit. For me having no inputs on the board and generating hiss just from the preamps is indicating and issue. At the least that better pre's are in order.
 
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