Simple question: How many dB to record at?

  • Thread starter Thread starter Dusty Ol' Bones
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The monitors are too low on the desk! Raise them up so that they're at ear level. Also, the left monitor is at the wrong angle, and the right one seems off too; both speakers should be firing at ear-level, meeting at a point just behind your head. Your head is at one point of an equilateral triangle. If you have to, move back towards that duvet.
 
What might be an interesting experiment, and this pretty much how noise-cancelling headphones work.
1. Set up a mic and record a few minutes of just ambient room noise.
2. Record your guitar and singing on separate tracks.
3. Invert the phase on the room recording.
4. Mix them all together on a bus or a group.
The theory is that mixing the inverted room noise track with the main track, the room noise should cancel out the noise on guitar/vocal track.
You are essentially creating a differential amplifier with the multiple tracks. More of less the same way balanced inputs work.
Never tried it, but theoretically possible.
 
OMG, that might sound like it would work, but unless the waves exactly match up (which is almost impossible), it can actually increase the noise level, It would be no different that having multiple tracks of tape hiss.

It would be a lot easier to use a noise reduction plugin, and make sure you have several seconds of room noise to sample, so the plug in can apply the proper filtering. It sometimes works, but might also change the sound of the stuff that you want.

Noise cancelling headphones actually sample the outside noise, and adds the inverted signal, so you have the exact same sound being combined.
 
TalismanRich said:
OMG, that might sound like it would work, but unless the waves exactly match up (which is almost impossible), it can actually increase the noise level, It would be no different that having multiple tracks of tape hiss.

It would be a lot easier to use a noise reduction plugin, and make sure you have several seconds of room noise to sample, so the plug in can apply the proper filtering. It sometimes works, but might also change the sound of the stuff that you want.

Noise cancelling headphones actually sample the outside noise, and adds the inverted signal, so you have the exact same sound being combined.
Click to expand...
And... balanced lines do NOT work by inversion of the signal as I explained in another thread. It is the IMPEDANCES that are "balanced".

Dave.
 
Hate to be that guy but compressors don't 'bring up the low points' and noise cancelling headphones don't sample noise from a few minutes ago.
These solutions will either not help or make the problem worse.
 
ecc83 said:
And... balanced lines do NOT work by inversion of the signal as I explained in another thread. It is the IMPEDANCES that are "balanced".
Click to expand...
Balanced Line - Wiki
"Many explanations of balanced lines assume symmetric signals (i.e. signals equal in magnitude but of opposite polarity) but this can lead to confusion of the two concepts—signal symmetry and balanced lines are quite independent of each other." -G. Ballou, Handbook for Sound Engineers, Fifth Edition, Taylor & Francis, 2015, p. 1267–1268.
You are certainly correct, as the two terms are used interchangeably, but, in fact, are not interchangeable.
"Signal symmetry", using a microphone as an example, is achieved using a Common-Mode Rejection amplifier.

1739824729066.webp

This circuit is a Common-Mode Rejection amplifier.
A1 & A2 are non-inverting op-amps where A (gain) = (1+Rf/Ri). Each op-amp has a non-inverting gain of 2. (In this case, we will not include Rg (amplifier gain resistor).
Input impedance is effectively infinite, output impedance is effectively = 0. (Ideal op-amp)
Hot and Cold inputs are 180o out of phase.
Noise present on both the Hot and Cold inputs is equal amplitude and equal phase. (This is the Common-Mode noise to be eliminated)
Vin = 1V RMS, 1kHz sine.
A1(+) input receives a negative going 1V sine wave.
A2(+) input received a positive going 1V sine wave.
At a gain of 2, the output of A2 will be a 1V positive going sine wave, minus any noise presented at the inputs of A1. (As the output of the op-amp wants to make both inputs equal.
That said, the output impedance of this circuit is essentially zero. To BALANCE the impedance, from output to input another component is necessary. i.e. a transformer.
At the end of the day, a TRS/XLR input, into this circuit will present a noise-free signal to an impedance matching transformer to the input
 
TalismanRich said:
OMG, that might sound like it would work, but unless the waves exactly match up (which is almost impossible), it can actually increase the noise level, It would be no different that having multiple tracks of tape hiss.
Click to expand...
Yeah, it could. I think if you take into account the latency. i.e. phase shift, at the end of the day, it would significantly reduce the noise.
It is being used in automotive applications already. I can't cite anything, but I do remember that noise cancellation tech in the cockpit of an auto made people slightly unsettled.
Here's a link to Bose:
BOSE NC Tech
I might try it just for yucks.
EDIT: my comment is to address your comment that the waves will not align. That's the phase shift.
 
The fundamental difference between what you're describing and noise cancelling headphones is that with noise cancelling headphones the desired audio,
your mp3 or whatever, is already isolated, as is the noise.

The idea of recording a sample of some of the noise might sound nice but unless that noise is controlled, repetitive and predictable, not just to your ear but in a measurable way, like a sine wave for example, it's not going to cancel with anything.

Forgive me for being dismissive but I feel like this thread is a few posts away from suggesting the OP buy another identical computer and set it out 180 degrees out of "phase" with his original one.
 
Steenamaroo said:
Forgive me for being dismissive but I feel like this thread is a few posts away from suggesting the OP buy another identical computer and set it out 180 degrees out of "phase" with his original one.
Click to expand...
Now THAT is a novel idea!!! So simple and effective. Just turn the plug around so it runs backwards. :ROFLMAO:
 
Old Music Guy said:
Balanced Line - Wiki
"Many explanations of balanced lines assume symmetric signals (i.e. signals equal in magnitude but of opposite polarity) but this can lead to confusion of the two concepts—signal symmetry and balanced lines are quite independent of each other." -G. Ballou, Handbook for Sound Engineers, Fifth Edition, Taylor & Francis, 2015, p. 1267–1268.
You are certainly correct, as the two terms are used interchangeably, but, in fact, are not interchangeable.
"Signal symmetry", using a microphone as an example, is achieved using a Common-Mode Rejection amplifier.

View attachment 149123
This circuit is a Common-Mode Rejection amplifier.
A1 & A2 are non-inverting op-amps where A (gain) = (1+Rf/Ri). Each op-amp has a non-inverting gain of 2. (In this case, we will not include Rg (amplifier gain resistor).
Input impedance is effectively infinite, output impedance is effectively = 0. (Ideal op-amp)
Hot and Cold inputs are 180o out of phase.
Noise present on both the Hot and Cold inputs is equal amplitude and equal phase. (This is the Common-Mode noise to be eliminated)
Vin = 1V RMS, 1kHz sine.
A1(+) input receives a negative going 1V sine wave.
A2(+) input received a positive going 1V sine wave.
At a gain of 2, the output of A2 will be a 1V positive going sine wave, minus any noise presented at the inputs of A1. (As the output of the op-amp wants to make both inputs equal.
That said, the output impedance of this circuit is essentially zero. To BALANCE the impedance, from output to input another component is necessary. i.e. a transformer.
At the end of the day, a TRS/XLR input, into this circuit will present a noise-free signal to an impedance matching transformer to the input
Click to expand...
Yes, you need an input device that does not respond to common mode signals (very much). That can be a transformer or a differential amplifier but the big difference between a balanced line "system" is that the noise reduction is carried out because the various impednaces are "balanced" at the input. Not because of some polarity cancellation by a derived 'noise' signal.

The common mode rejection is greatest when the two input resistances are much greater than the source resistances.
 
Well if the forum of home recording enthusiasts is going to be split between those who took college physics and those who did not, count me with the nots. I stand in solidarity with the artists that didn't ace their STEM courses, who don't know music theory or what key they're playing in. My recordings may not sound all shiny and polished like Brittany Spears, but I'm still able to get my message across.

Much thanks to those who helped and contributed!
 
Dusty Ol' Bones said:
Well if the forum of home recording enthusiasts is going to be split between those who took college physics and those who did not, count me with the nots. I stand in solidarity with the artists that didn't ace their STEM courses, who don't know music theory or what key they're playing in. My recordings may not sound all shiny and polished like Brittany Spears, but I'm still able to get my message across.

Much thanks to those who helped and contributed!
Click to expand...
Well I am sorry you feel that way 'Bones. I would have thought the arguments between "Art, Science and Religion" had been resolved long ago, at least among reasonable people?

You cannot have any kind of "art" without technology (and hence "science") The first instrument was surely the drum? A hollow tree trunk and the "artistically gifted" caveman/woman would have soon worked out that different sized trunks gave a different sound and gathering several together, each with a different "note" made for more interesting tooons!

Even the human voice sounded better in a large cave or some natural land formation and so millennia on we have concert halls.

All the instruments of the orchestra evolved as makers found ways to make them louder or easier to play or span a greater range (e.g. valved brass) Q Leo Fender or whoever you consider 'invented' the electric axe!

Understanding some of the physics of sound, instruments and recording technology takes not one iota from the art and talent needed to produce good music. In fact IMHO it enhances it. Take George Martin? A supreme musician but also at home with recording technology. Could the Fab Four have produced such super stuff had he not been around? I don't think so.

I take New Scientist every week and understand little of it but the struggle to understand the universe does NOT for me take away any of the wonder of it. The Moon is no less beautiful for us understanding what it is made of, HTF it stays there or how it likely got formed!

Dave.
 
There's no need to be defensive.
You've come looking for help and advice and you're getting it.

I'll never discourage someone from experimenting to learn but there is value in saying "that's not how it works" if that's not how something works.

No one's criticising your recordings and no one's suggesting you should pick a side.

There's one side - People on a forum trying to learn.
 
I didn't know that you needed a physics degree to understand something as simple as noise. But I guess I was wrong.

I was looking at reviews of a hand held SPL meter, and saw someone's comment that it didn't work because when he had it in a quiet room it should read something like 0 but instead it was showing 40 or so. Obviously this person hasn't got a clue what a sound level really is. Most houses and quiet offices are going to be around 30-40dBa. Even with just a refrigerator running you can easily hit 40. A little traffic from the road a quarter mile away is going to show up. I'm sitting in my den, and my room is measuring 36dB. That's nowhere close to quiet enough for recording unless I'm recording my Marshall and the mic is 6 inches from the speaker! Simply singing at about 10 inches from the meter I'm registering 83dB max. SO my signal to noise ratio is 47db which would suck for a studio recording.

It doesn't take a PhD to do a simple experiment. Turn on your recorder and watch the meter bouncing around and look at the number. Then start singing and look a the number. Surely you took simple arithmetic in 2nd grade!

Why do people make things so hard?
 
Dusty Ol' Bones said:
I stand in solidarity with the artists that didn't ace their STEM courses, who don't know music theory or what key they're playing in. My recordings may not sound all shiny and polished like Brittany Spears, but I'm still able to get my message across.
Click to expand...
Gut punch, but well deserved. I think, personally, I spend more time worrying about niggling little details that completely drain me of the only thing I really need, and that's creativity.
Thanks @Dusty Ol' Bones for the reality check.
 
I really have lost touch with OP's question in the original post. It's a basic question. Maybe it would make more sense to look at it backwards. It should be quite easy to mix guitar and vocals AFTER they have been recorded. If they have both been recorded at the same level, and on different tracks, it makes the most sense to just mix for balance after the fact.
I've run into issues with my mates that when I try to record us at a certain level, in post, it's never correct, and I need to mix. No problem.
Better to be hot than not.
 
Sorry about the strong words in my defensive post and I certainly did not mean to offend. @Old Music Guy made a good point, which is that I think some of us lost touch with the OP. Myself included, and that's not you guys' fault.

I have an eye for detail that sometimes interferes with my tendency to overthink things, so when the thread took the direction of noise canceling headphones, disagreements over compression, etc, it got over my head and I was trying to keep things simple, as the thread title suggests. I know my place and I know all of you have way more knowledge and experience than me, which should be reflected in my gracious replies to y'alls thoughtful and helpful posts.... up until the point things got over my head.

A little about me. I have a graduate degree in a social science. During undergrad, I took all my science electives in the life sciences, biology and such, completely evading chemistry and physics. Took honors physics in high school but I can't recall anything more than the doppler effect when it comes to sound waves.

On a more positive note, I took a lot of the advice I've gotten from you all in this thread and recent others, and went back in to the studio this week for overdubs on a song I'm working on. I set up our makeshift sound booth the same but placed the SDC mics closer to my guitar player, which allowed me to decrease the input gain on those two channels. That's all I was really looking to do.

@TalismanRich, you are correct that alls I really needed to do was experiment with moving mics around, because I found a sweeter spot than I had before. Thank you.

TL/DR: Thanks to some friends on HRF, I got a better sound. And I didn't have to activate the scientific method or crack one damn physics book.
 
ecc83 said:
Well I am sorry you feel that way 'Bones. I would have thought the arguments between "Art, Science and Religion" had been resolved long ago, at least among reasonable people?

You cannot have any kind of "art" without technology (and hence "science") The first instrument was surely the drum? A hollow tree trunk and the "artistically gifted" caveman/woman would have soon worked out that different sized trunks gave a different sound and gathering several together, each with a different "note" made for more interesting tooons!

Even the human voice sounded better in a large cave or some natural land formation and so millennia on we have concert halls.

All the instruments of the orchestra evolved as makers found ways to make them louder or easier to play or span a greater range (e.g. valved brass) Q Leo Fender or whoever you consider 'invented' the electric axe!

Understanding some of the physics of sound, instruments and recording technology takes not one iota from the art and talent needed to produce good music. In fact IMHO it enhances it. Take George Martin? A supreme musician but also at home with recording technology. Could the Fab Four have produced such super stuff had he not been around? I don't think so.

I take New Scientist every week and understand little of it but the struggle to understand the universe does NOT for me take away any of the wonder of it. The Moon is no less beautiful for us understanding what it is made of, HTF it stays there or how it likely got formed!

Dave.
Click to expand...
I'm not picking fights, just felt the need to address this one separately.

I strive to be a reasonable person but don't always hit that target. We can agree to disagree and still be friends, right? I am not anti physics or science. I'm fully vaxxed against covid and other ailments, just in case one were to wonder where I stand on science in general.

Your post here is pretty spot on and accurate. You are correct that there would be no "art" without technology, or "science." However, this comes out like a chicken/egg argument. Which came first, the art or the science? Sure, the original artists needed technology, like a stick to beat the log with. But if they did not invent or innovate the stick and just picked it up off the ground, is it really technology? Or just a stick? Do you actually believe that cave folks brought out a measuring tape, tuning forks, and writing implements to record the notes for future reference? Do you think they wrote out a hypothesis to test against previous log experiments? Do you think the vocal cave artists busted out their sound meters and tested which cave had better reverberation as a function of what the meter read?

A person would have to not be reasonable to actually believe the cave men and women had one iota of this stuff on their mind while they were thumping logs. In fact, since religion was brought into the conversation, they most likely associated the new sounds with something more supernatural than waves on a meter. I would argue that by beating logs, they were attempting to communicate with the God of Noise so he would rain thunder and rain down upon on their gardens for nourishment and sustenance of life.
 
Dusty Ol' Bones said:
I'm not picking fights, just felt the need to address this one separately.

I strive to be a reasonable person but don't always hit that target. We can agree to disagree and still be friends, right? I am not anti physics or science. I'm fully vaxxed against covid and other ailments, just in case one were to wonder where I stand on science in general.

Your post here is pretty spot on and accurate. You are correct that there would be no "art" without technology, or "science." However, this comes out like a chicken/egg argument. Which came first, the art or the science? Sure, the original artists needed technology, like a stick to beat the log with. But if they did not invent or innovate the stick and just picked it up off the ground, is it really technology? Or just a stick? Do you actually believe that cave folks brought out a measuring tape, tuning forks, and writing implements to record the notes for future reference? Do you think they wrote out a hypothesis to test against previous log experiments? Do you think the vocal cave artists busted out their sound meters and tested which cave had better reverberation as a function of what the meter read?

A person would have to not be reasonable to actually believe the cave men and women had one iota of this stuff on their mind while they were thumping logs. In fact, since religion was brought into the conversation, they most likely associated the new sounds with something more supernatural than waves on a meter. I would argue that by beating logs, they were attempting to communicate with the God of Noise so he would rain thunder and rain down upon on their gardens for nourishment and sustenance of life.
Click to expand...
But you are not a caveman, you are in THIS TECHNOLOGICAL world. My point was that over centuries ways of producing pleasant sounds were developed and 'perfected'. As society changed people wanted to listen to music en masse and that meant louder instruments so the iron frame for the piano was developed for instance. Wind instrument bores got bigger. They understood the science of sound and applied it.

Just post WWll almost nobody could afford any kind of recording gear and studios were very rigidly structured places. There were the musician and there were the recording engineers. Between the two was the producer who, (the good ones) had a foot in both camps. The musicians mainly did as they were told! This arrangement obtained more or less up to the '60 when the Beatles broke it.

But you my friend are doubly buggered! You can't afford weeks at Abbey road but neither are you a recording engineer. What is great is that almost everyone today can afford a basic recording setup that knocks chunks off the sound quality the Beatles could achieve...YOU can record for hours for free (look the price of a NAB reel of tape!) you can do infinite overdubs, undos.

Worth learning just a teensy bit of physics?

Dave.
 
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