Noise Floor

[Ambio]

I have read many comments about hearing lower noise floor from your system after changing something. Can FM share what are they really referring to when they say they hear lower noise floor? To my non-technical mind, the noise floor that matters to me is the audible sound through the speakers with zero signal. Ideally, at standby with the volume control at the usual listening level there should be zero noise from the speakers. You can also use the Denons test CD to measure your system's overall noise floor.

The next biggest noise floor in our room is the natural noise that seemed to exist no matter how much we sound proof them. My rooms measurement is 34dB without the aircond. It was so quiet that you could hear your natural otoacoustic emission. The noise level went up to 38dB with the aircond and as time goes by the aircond is getting noisier and now there room is relatively noisy at 43dB. Using this level as the threshold for my system, the lowest audible sound was the decay of the piano notes, i.e. about 3 or 4 seconds until the lifting of the foot from the pedal.

Looking at most equipment's specs and provided you are free from transformers hum and RFI and EMI leaking to your speakers, how do you really hear a lower noise floor than the room itself? Unless there is a serious mismatch of gain between your source and amplifier.

Any thoughts? What is the rooms noise floor?

 

[Santy]

I am not a techie either, but noise floor is not what is commonly construed as the pink noise or buzz or hum but the music level below which some of the details in the music might get lost; the decay of some instruments for instance. Its not the level at which you hear the noise when no music is playing. Its the lowest sound level at which you still have measurable music information. I believe it also correlates with the SNR or dynamic range of the system. If a system has a low noise floor, it would have a wider dynamic range. Its like having more darker shades in a gradient of white to black. There may be no hiss or hum in a system even at high volumes but it can still have a high noise floor. The external electrical noise can indeed affect the noise floor of the system. Balanced connection in my experience (strictly) has lower noise floor compared to unbalanced connection with everything else remaining the same.

Your question does make sense, whether it would matter to have a low noise floor when the room itself is not quiet enough to take advantage. But we can always increase the volume and hear more low volume details. Do not forget headphones while discussing about the quietness of the room! They have an advantage here.

 

[Thad E Ginathom]

Confusion of definitions! I'm sure that the real meaning of these terms must be simply stated and known to engineers, but audiophiles like to make it up as they go along. What follows is more opinion*.

to my non-technical mind, the noise floor that matters to me is the audible sound through the speakers with zero signal.

I agree with Ambio on this one, and stuff that buzzed, hummed and hissed, audibly when not masked by music, should be a thing of the past --- by several decades!

Thus I once replied to "I replaced x with y and the noise floor dropped," with "With the possible exception of turntables, If I could hear the noise floor I'd throw the equipment away!"

Of course there is noise, and there is a noise floor. When we look at equipment reviews that include measurements we can see that, and it may look pretty spiky and horrible --- until one looks at the scale on the left, and one can realise why even full volume plays silence at the speakers. I don't think there is anything there than can, as it were, eat the low level details in music.

However, they certainly can and do disappear in the ambient noise, but that has nothing to do with the equipment.

Any thoughts? What is the rooms noise floor?

If you go to this audiocheck.net page you can find out the actual dynamic range of your equipment/ears/environment. I don't remember the number, but it showed me that there was certainly no point whatsoever in agonising over whether a component had a SNR of 105dB or 109db!

My headphones are open backed, so there is no isolation at all. Sure, I could improve the numbers with closed-back 'phones, but I have not yet learned to live with the shut-in feeling of closed-back. I'll try adding a good closed 'phone to the collection one day.

*the definitions are probably only a google away?

 

[Ambio]

I am not a techie either, but noise floor is not what is commonly construed as the pink noise or buzz or hum but the music level below which some of the details in the music might get lost; the decay of some instruments for instance..

Thank you very much for the definition. However, with respect, I have to disagree. Noise floor is total sum of all unwanted noise that wasn't in the original recorded sound. In fact, NF is actually categorized as pink, white, brown and blue noise. In the recording studio, the noise floor is made of the room's noise, other electronics noise and mainly from the preamplifier and microphones noise. It is the job for the recording engineer to determine the lowest level that could be recorded without being masked by the noise floor. At the same time his job also must take into consideration of the loudest passage so that the sound doesn't clip.

Its not the level at which you hear the noise when no music is playing. Its the lowest sound level at which you still have measurable music information..

Let's say, the lowest level in a recording is 30dB. Technically, I don't think that how the lowest level is determine as my recording engineer friend pointed out but let's assume that is the figure for a non-technical discussion. Let's say, the highest level is 100dB. Again, this is not going to happen as most of the recording's dynamic range did not cross 20dB.

Now, playing this music in a very quiet studio with the noise floor of 20dB, the lowest of 30dB (with x amount of power) should be audible. Now, if the room's noise floor (NF) is above 46dB (room plus your equipment), then to make the lowest sound audible we need to increase the volume to 56dB so that the loudness difference is relative to NF of the studio and your room. Now, the amp need to put up 128 times more power than in the studio. If the amp was using 100W to produce the 100dB in the studio then in your room you would need 12800Watt!!

To improve your system you replaced the cables and amplifier, you also installed a new air cond system and sound proof you room from the external noise. Now, the overall NF of your room and system is about 35dB. How would you describe low NF here? What will you be referring to?

Your question does make sense, whether it would matter to have a low noise floor when the room itself is not quiet enough to take advantage. But we can always increase the volume and hear more low volume details. Do not forget headphones while discussing about the quietness of the room! They have an advantage here.

As I described above, you cannot increase the volume without sacrificing the fidelity. The average amplifier power that we have is about 150W. Although the example above is not going to happen in real life as it very unlikely your listening level would touch 100dB in normal listening.

Going back to the question, how would you describe hearing a lower NF in a recording with the change of a cable or amplifier or a CD player? Whatever sound that you hear in a recording is the original sound that was intended to be recorded and the unwanted sound of studio (environment) , electrical and electronics noise. That will be all in the recording.

In most cases, the musical content will be around 85dB with 1Watt of power. The NF that would be in the recording would be in the low 20dBs. A better system will reveal the NF in the recording. Contrary to what we say, "I hear a lower noise floor" , you should be hearing more micro details of low sound including the NF.

Thad sums it up pretty well about the confusion NF.

 

[Santy]

I think there is a confusion here between acoustic noise (of the ambiance) and electronic noise (that affects the SNR) caused by the limitations in recording and playback devices and external electrical interference. While both affect the listening experience, it is best they are dealt separately. When I say details are lost, it means the music/ sound recorded below the electronic noise floor that cannot be heard or measured. And yes, as the question goes, whether the benefits of low noise floor in the system is of any advantage when the room's noise levels are higher, is to be understood better.

 

[Ambio]

This is getting more and more confusing. Just spent 2 solid hours learning about dBU, dBV, dBFS and SNR. In the end, I am now more confused.

I am confused when someone says they could hear a lower noise floor. The point I am trying to make was - there should be no noise floor audible even in a entry level CD player or Amplifier at normal listening level. If you hear any noise other than what's in the recording then it should be coming from your equipment, especially the amplifiers or cables picking up RFI.

This guy in Audiogon asked the same question and ended up not getting the answer.

Blackness - how quiet does it need to be?
In almost all gear of any substantial value the concept of the blackness, quietness or low noise floor comes up. A reviewer might say that the noise floor was noticably lower when reviewing a particular piece compared to another. Now I get that low noise translates roughly to being able to hear more music and nuanced detail. Thing is, when I turn on my system and no music is going through it, I can't hear anything, unless I put my ear right up to the speaker and the AC isn't running and the fan isn't on, etc. And with music on the only thing I hear is any recorded hiss that might be from the recording. So what I dont get is when they say a piece of equipment sounds quieter, do they mean somehow that the hiss on the recording is lower? I cant see how that would be possible, or are they talking about the hiss of the equipment without muisc? In which case I cant hear it at all when sitting down on my couch. I don't have the world best gear, so I'm thinking are they overplaying the "quiet" card.
Last_lemming

To my understanding, signal to noise ratio is a measurement of noise and signal. It can be measured within the amplifer or source. The hisses and pops in the recordings are not NF that you should try to eliminate. It is the job of the mastering engineers to get rid of them but if they didn't then your equipment must retrieve them faithfully. The other aspect of SNR is the ambiance noise against the speakers.

An example of room SNR here.

The actual calculation of SNR ratio is

.

Is it possible for someone who heard lower NF describe the tracks and equipment to make some useful comparison to understand this topic better? As far as I am concerned, when the volume is at normal listening level but without any signal I don't hear any audible hiss or sound which usually associated with the equipment's internal noise. I don't see how I could better this with the room's noise of 40dB.

 

[prem]

In my understanding, there are 3 noises that affect our listening. Electrical noise, mechanical noise and room noise. All these noises mix with the audio signal. As a result low level information which creates the ambience is lost. Also these noises could affect high frequency.

Electrical noise is because of the rf and emi riding on the power lines. How well our equipments power supply reject this noise determines how clean the audio signal is. Adding an isolation transformer or a power conditioner or a CVT helps further in cleaning up this noise. Naturally all of these external devices have their own plus and negative points

Mechanical noises could be because of the transformers or loose sockets or flimsy chassis. How well the chassis is designed such that the vibrations get drained out determines how much of mechanical noise is there in the system. Many people use various devices like spikes, cones, specially designed racks, etc to drain out the vibrations. Vibrations in the system manifest as resonances.

Finally there is room noise. This is not to be confused with reflections. Reflections need to be treated neverthless. Room noise is basically external noise from the surrounding as well as rf and emi in the air which is generated by wifi, cells, tv, etc. For this one can look at sound proofing which most studios do and to reduce air borne rf and emi one can use crystals which have piezo electric effect or Schumann resonance devices or specific resonators designed to alleviate these harmful noises.

Reduction in all three noises naturally result in one being able to hear more of the audio signal.

 

[Thad E Ginathom]

When I say details are lost, it means the music/ sound recorded below the electronic noise floor that cannot be heard or measured.

Cannot be heard... so no details, or sound, of any kind is lost.

or measured... It can be measured. Noise measurement is common in tests and reviews.

The ultimate threshold of human hearing is just above the sound that the atoms make as they bounce against your eardrum.

What is the "sound" we hear when we find ourselves in a really, really quiet place? I'd like to think we might be hearing some of those atoms, but I rather doubt it. Time for google, I suppose... Later

 

[Nikhil]

I am confused when someone says they could hear a lower noise floor. The point I am trying to make was - there should be no noise floor audible even in a entry level CD player or Amplifier at normal listening level. If you hear any noise other than what's in the recording then it should be coming from your equipment, especially the amplifiers or cables picking up RFI.

....

Here is a simplified way of looking at noise and how it affects your sound. From the figure below you will see that you may not even realize that there is noise in your system until someone shows you or you reduce/eliminate the noise in your setup (Power conditioning, cables, etc.)

The term Noise Floor is technical jargon from Signal Analysis which has transferred over to Audio. All systems have a sound which can be divided into the Signal (the good part that we want to hear) and Noise (the background noise we do not want). Lowering the Noise Floor relates to lowering/eliminating the unwanted noise so that the pristine signal is easily heard.

 

[Ambio]

What is Ut in the graph?

 

[Nikhil]

What is Ut in the graph?

It's just a signal notation as a function of time.

 

[jls001]

If you view an audio device as an electrical system (which it is), it consists of many components like resistors, capacitors, inductors, diodes, transistors, integrated circuits, etc. Each of these components generate their own spurious signal that gets added to the actual audio signal. Noise is always additive (as shown in Nikhil's diagram) and the sum of all the spurious signals at the final output of the device/system when there is NO audio input signal is the device/system noise. If you study the detailed specs of (for example) a transistor or a DAC chip, the noise floor is mentioned. This is the self noise of the component and will be present irrespective of whether there is input or not. And it is present from DC to infinity. It is an absolute number measurable as so many uV. A line level signal is usually in the 1-2 volts range. Compared to a noise signal which is a millionth order smaller, the arithmetic becomes cumbersome, so noise is usually expressed in the log scale, and referenced - IIRC - to the level of the desirable audio signal (please correct me if I got the reference wrong - it could as well be referenced to a microvolt and described as dBuV). So if the sum of all noises is -86 dB below the desired signal, -86 dB is the noise floor of that device/system.

When listening to a lowered noise floor, one can better feel/hear the silences between notes as being quieter. The net effect is improved low-level detail retrieval and improved micro dynamics (one can better hear tiny changes in loudness - e.g. A triangle remains audible as an independent and distinct event in the midst of loud tympani).

That was the electrical side of noise.

Prem has given an excellent explanation of acoustic and mechanical noises. Just to add a line here - if the ambient acoustic noise of a room is for example 55 dB, the faintest audio signal that can be distinguished above this ambient noise must be played at > 55 dB. So a more silent room is desirable to enjoy lower level details in music.

 

[prem]

Ambio, external factors affect noise floor much more. Which is why in reviews you read statements like a power conditioner was introduced and the noise floor dropped.

Basically S/N is measured at 1 watt. If S/N at 1 watt is 50 then at 100 watts it will be 70. Thus by raising the volume you can improve S/N.

Further S/N assumes perfect input signal which is normally never the case. There are many external noises which affect the input signal. Thus to get a lower noise floor, it is important to reduce these external noises.

 

[Thad E Ginathom]

I didn't read all (Later, I have to go out... ) but Nikhil, I'd call the kind of noise you illustrate distortion. But I'd agree I suppose that that is a kind of noise.

More thought later

 

[reignofchaos]

The noise floor in my listening room as measured by an android app (so only approximate) is 40dB. So no matter what I try, this can't be lowered without significant room deadening etc which has other repurcussions.

What I really care about is whether I can hear any noise from the speaker at the normal volume level (around -24dB according to my preamplifier's display) when no signal is being passed or when an empty wave file with no sound is being played via my dac (analog will obviously have hiss). In this state, even if I press my ear onto the tweeter of the loudspeaker, I do not hear a thing - let alone any noise at the listening position.

I think that is good enough as far as I'm concerned and I have stopped bothering about the noise floor or any other noise in my system.

 

[Ambio]

It's just a signal notation as a function of time.

Thanx but I don't think the noise floor would alter the signal the way it was shown in the graph. If noise some how changes the fundamental frequency like shown in the graph then I don't think audio compression such as MP3 would work. *But if it is then we may have an explanation why we hear lower NF.*

...
1) *So if the sum of all noises *is -86 dB below the desired signal, -86 dB is the noise floor of that device/system.

2) When listening to a lowered noise floor, one can better feel/hear the silences between notes as being quieter.*

3) *if the ambient acoustic noise of a room is for example 55 dB, the faintest audio signal that can be distinguished above this ambient noise must be played at > 55 dB. So a more silent room is desirable to enjoy lower level details in music.

I have numbered the relevant parts for cross reference.*

1) Well.... I thought so but the more I read about noise floor and SNR, the -86 dB may not be the noise floor. Could you give some example, please?

2) the silence between the two notes which I can confirm no signal exist by running a spectrogram is the air cond noise or without the air cond it will be no noise although the digital SPL meter shows 34 dB.

3) it is possible to hear below ambient noise depending on the dominant frequency of the noise floor.

?...

Basically S/N is measured at 1 watt. If S/N at 1 watt is 50 then at 100 watts it will be 70. Thus by raising the volume you can improve S/N.*
...

Wouldn't increasing the volume would also increase the level of noise floor?

I didn't read all (Later, I have to go out... ) but Nikhil, I'd call the kind of noise you illustrate distortion. But I'd agree I suppose that that is a kind of noise.*

More thought later

IT is an interesting graph but I read the website from which the graph was extracted and they clearly used that to describe noise (SNR).*

 

[prem]

No Ambio. The noise floor won't increase by increasing volume.

 

[dheerajin]

For me noise floor is when someone is dancing with shoes on with good music is thrown by system... So system should be musical and there should be minimal noise accompanied so that we can add human noise....that is the ultimate listening by brain...not by influenced human mind

 

[dheerajin]

For me noise floor is when someone is dancing with shoes on with good music is thrown by system... So system should be musical and there should be minimal noise accompanied so that we can add human noise....that is the ultimate listening by brain...not by influenced human mind

[emoji6] [emoji6] [emoji2] [emoji2] [emoji2] just on the lighter note

 

[Thad E Ginathom]

<<Interesting comments, but I've been to two concerts today, and somehow ...I can't turn my brain on! >>