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Topic: Any tests show audible noise floor? (Read 18886 times) previous topic - next topic
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Any tests show audible noise floor?

Have their been any tests to show the audible noise floor of Dacs ? Ie when can we hear the noise -55 db ? Etc etc
What were the results ?

Any tests show audible noise floor?

Reply #1 –
Strongly simplified: consider the DAC produces a noise floor of -55 dBV, outputs 1V (0 dBV) and the gain of the amplifier is 27 dB and the sensitivity of your speakers 87 dB SPL/2.83V (9 dBV) @ 1m.

So with the volume turned up all the way the max SPL would be 105 dB SPL with the DAC noise floor at 50 dB SPL. If this noise is white then it would be quite annoying with nothing else playing in a silent room.
"I hear it when I see it."

Any tests show audible noise floor?

Reply #2 –
Hi,
What Im wondering is if there is  a signal to noise ratio that is considered audible and f so what is it ? Whether it be at 1m 2m whatever - have any test like that been done (subjective listening tests, abx ) etc Really though I was thinking of a simple simple loopback test (no mic/no speakers involved)  as the one you can do with REW (room eq wizard)  to calibrate the sound card, there is also software specifically for testing your interface - I can't remember the name of it - so I was wondering if there had been anything done on the test results from this kind of software and audibility.

So in the case of this review it says the ADA8000 has a

" roughly 70 dB S/N ratio at the +4 dB setting"

http://www.audiorail.com/ADA8000.htm

Im assuming this is well below audible level (-66 db for white noise) - or is it ? - Im assuming they run the test by just looping the output of the Dac back into its input (rather than using a mic).

Any tests show audible noise floor?

Reply #3 –
Quote from: augustine on
What Im wondering is if there is  a signal to noise ratio that is considered audible and f so what is it ?


There are probably hundreds of threads on this.  I'd suggest looking at any of the 16 bit vs. 24 bit threads.  Usually people agree that the noise floor can be audible in 16 bit audio (~96dB) but that its low enough that its unlikely to be a serious problem for real audio.  Since you haven't specified what you are doing, I'd say that about 16 bit audio is probably a good SNR to aim for if you want transparency. 

Quote from: augustine on
Whether it be at 1m 2m whatever - have any test like that been done (subjective listening tests, abx ) etc Really though I was thinking of a simple simple loopback test (no mic/no speakers involved)  as the one you can do with REW (room eq wizard)  to calibrate the sound card, there is also software specifically for testing your interface - I can't remember the name of it - so I was wondering if there had been anything done on the test results from this kind of software and audibility.


It is not possible to assess audibility without speakers or headphones.  You have to listen to audio to do that test. 

Quote from: augustine on
Im assuming this is well below audible level (-66 db for white noise) - or is it ? - Im assuming they run the test by just looping the output of the Dac back into its input (rather than using a mic).


That would be definitely audible, however if you look at those loopback test results, the noise floor on that device is about -95 dB. 

Any tests show audible noise floor?

Reply #4 –
Quote from: saratoga on
Quote from: augustine on
What Im wondering is if there is  a signal to noise ratio that is considered audible and f so what is it ?


There are probably hundreds of threads on this.  I'd suggest looking at any of the 16 bit vs. 24 bit threads.  Usually people agree that the noise floor can be audible in 16 bit audio (~96dB) but that its low enough that its unlikely to be a serious problem for real audio.  Since you haven't specified what you are doing, I'd say that about 16 bit audio is probably a good SNR to aim for if you want transparency. 

Quote from: augustine on
Whether it be at 1m 2m whatever - have any test like that been done (subjective listening tests, abx ) etc Really though I was thinking of a simple simple loopback test (no mic/no speakers involved)  as the one you can do with REW (room eq wizard)  to calibrate the sound card, there is also software specifically for testing your interface - I can't remember the name of it - so I was wondering if there had been anything done on the test results from this kind of software and audibility.


It is not possible to assess audibility without speakers or headphones.  You have to listen to audio to do that test. 

Quote from: augustine on
Im assuming this is well below audible level (-66 db for white noise) - or is it ? - Im assuming they run the test by just looping the output of the Dac back into its input (rather than using a mic).


That would be definitely audible, however if you look at those loopback test results, the noise floor on that device is about -95 dB.


I've done quite a lot of searching on this and couldn't find anything.
.To clarify ; what I was trying to ask is whether objective measurements (loopback) have been compared to audibility (of course you a correct that part would need speakers and of course would vary between individuals ). The reason I am asking this is someone said the ada8000 had a noisy dac that had a clearly audible noise floor.  I've got one and can't hear a damn thing plus my loopback measurements showed flate response, good decay times across the spectrum and low  thd. So I guess I am looking for an objective measurement to back up my subjective opinion - that any noise coming out of the Dac is well below audible level - unless of course I am wrong.

Any tests show audible noise floor?

Reply #5 –
Quote from: augustine on
The reason I am asking this is someone said the ada8000 had a noisy dac that had a clearly audible noise floor.  I've got one and can't hear a damn thing plus my loopback measurements showed flate response, good decay times across the spectrum and low  thd. So I guess I am looking for an objective measurement to back up my subjective opinion - that any noise coming out of the Dac is well below audible level - unless of course I am wrong.

The burden of proof lies on the individual claiming the ada8000 had a clearly audible noise floor.  Trying to find evidence to the contrary is futile.  You're wasting your time.

Any tests show audible noise floor?

Reply #6 –
Quote from: greynol on
Quote from: augustine on
The reason I am asking this is someone said the ada8000 had a noisy dac that had a clearly audible noise floor.  I've got one and can't hear a damn thing plus my loopback measurements showed flate response, good decay times across the spectrum and low  thd. So I guess I am looking for an objective measurement to back up my subjective opinion - that any noise coming out of the Dac is well below audible level - unless of course I am wrong.

The burden of proof lies on the individual claiming the ada8000 had a clearly audible noise floor.  Trying to find evidence to the contrary is futile.  You're wasting your time.


not really there's plenty of aspects of audio audibility  has been assesed by a combination of objective measurements and subjective listening tests. For example the human hearing range. If someone told me they could hear 400000000 khz I would have plenty evidence to the contrary. And besides I find the topic interesting.

Any tests show audible noise floor?

Reply #7 –
Quote from: augustine on
I've done quite a lot of searching on this and couldn't find anything.


Check out those threads I suggested above. This has been discussed endlessly.

Quote from: augustine on
So I guess I am looking for an objective measurement to back up my subjective opinion - that any noise coming out of the Dac is well below audible level - unless of course I am wrong.


I think I already answered this?  The noise floor will be audible, but probably low enough that it doesn't matter for most things.  If that makes it "noisy" is a matter of opinion.

Any tests show audible noise floor?

Reply #9 –
Quote from: saratoga on
Quote from: augustine on
I've done quite a lot of searching on this and couldn't find anything.


Check out those threads I suggested above. This has been discussed endlessly.

Quote from: augustine on
So I guess I am looking for an objective measurement to back up my subjective opinion - that any noise coming out of the Dac is well below audible level - unless of course I am wrong.


I think I already answered this?  The noise floor will be audible, but probably low enough that it doesn't matter for most things.  If that makes it "noisy" is a matter of opinion.



You said -66  db would definately be audible however this device was -95 db and that 16 bit -96 db was "generally agreed" lowest audible level - so one db above what is generally considered audible for 16 bit ? So probably not audible for some as everyone's hearing varies ?
Also I'm not really looking for what people agree on but actual tests abx or otherwise, papers etc if such exist...

Any tests show audible noise floor?

Reply #10 –
Quote from: augustine on
You said -66  db would definately be audible however this device was -95 db and that 16 bit -96 db was "generally agreed" lowest audible level - so one db above what is generally considered audible for 16 bit ? So probably not audible for some as everyone's hearing varies ?


I didn't say that -96dB was the lowest audible level.  That would probably be wrong.

Any tests show audible noise floor?

Reply #11 –
Quote from: saratoga on
Quote from: augustine on
You said -66  db would definately be audible however this device was -95 db and that 16 bit -96 db was "generally agreed" lowest audible level - so one db above what is generally considered audible for 16 bit ? So probably not audible for some as everyone's hearing varies ?


I didn't say that -96dB was the lowest audible level.  That would probably be wrong.


Ah ok so it seemed very low to me. So what did you mean by

Usually people agree that the noise floor can be audible in 16 bit audio (~96dB

I am aware now that is not a minus.

Please clarify .

Any tests show audible noise floor?

Reply #12 –
Quote from: augustine on
I am aware now that is not a minus.


Sorry that should have been a minus.  I meant that people usually agree that the noise floor of 16 bit audio can be audible in some circumstances. 

Any tests show audible noise floor?

Reply #13 –
Quote from: saratoga on
Quote from: augustine on
I am aware now that is not a minus.


Sorry that should have been a minus.  I meant that people usually agree that the noise floor of 16 bit audio can be audible in some circumstances.


Not at all thanks for taking time to answer my questions. I must admit I am not entirely clear on the subject but I will sleep on it.

Any tests show audible noise floor?

Reply #14 –
Quote from: saratoga on
I meant that people usually agree that the noise floor of 16 bit audio can be audible in some circumstances.

With what signal, what level and what listening environment?

Regarding the -95dB measurement, that was a loop-back test, which could be limited by the performance of the ADC.

Then how do we relate this back to device that was measured and coupled with an anecdotal claim of audibility (which we've been tasked to disprove )?

Any tests show audible noise floor?

Reply #15 –
Quote from: augustine on
In a way greynol is correct I should be setting up a studio not discussing SNR on forums ! Don't tell him that though .

In more ways than that, I'm afraid.

Any tests show audible noise floor?

Reply #16 –
Quote from: greynol on
Quote from: saratoga on
I meant that people usually agree that the noise floor of 16 bit audio can be audible in some circumstances.

With what signal, what level and what listening environment?

Regarding the -95dB measurement, that was a loop-back test, which could be limited by the performance of the ADC.

Then how do we relate this back to device that was measured and coupled with an anecdotal claim of audibility (which we've been tasked to disprove )?


because as with the generally accepted human hearing range (frequency)  there is also generally accepted human hearing range of loudness (generally quoted as 0 db - 160 db but point being there is a "quietest" people can here as well as a "most high pitched" etc etc). So surely it's just comparing that range to the noise output of the device though obviously it depends where you have the volume control.

Any tests show audible noise floor?

Reply #17 –
There's 30 - 40 dB noise in your silent listening room.

"I hear it when I see it."

Any tests show audible noise floor?

Reply #19 –
Quote from: augustine on
because as with the generally accepted human hearing range (frequency)  there is also generally accepted human hearing range of loudness (generally quoted as 0 db - 160 db but point being there is a "quietest" people can here as well as a "most high pitched" etc etc). So surely it's just comparing that range to the noise output of the device though obviously it depends where you have the volume control.

That didn't answer either of my questions.  (HINT: "because" answers a why.  My questions are of the what and how variety. )

Any tests show audible noise floor?

Reply #20 –
Quote from: augustine on
because as with the generally accepted human hearing range (frequency)  there is also generally accepted human hearing range of loudness (generally quoted as 0 db - 160 db but point being there is a "quietest" people can here as well as a "most high pitched" etc etc). So surely it's just comparing that range to the noise output of the device though obviously it depends where you have the volume control.


It seems to me that different dB measures are getting mixed up here.

The human hearing range is (unsurprisingly) measured in dB(SPL), which is a measure of sound power, so it is nothing electrical. The dynamic range of a DAC is an electrical measure, obtained at its analog output. You can express it in % or in dB, and it means the ratio between the power of a full-scale sine wave signal, and the power of the background noise when there is no signal.

Just because you can express both with a dB figure, doesn't mean they can be exchanged willy nilly.

The limits of the dynamic range of human hearing are usually seen in the Fletcher Munson curves (google that if you don't know it already). It is apparent that there is a strong dependency on the frequency of the sound signal. When assessing the audibility of background noise, those curves have to be taken into account. As a consequence, it is customary to apply a frequency dependent weighting curve when measuring background noise. The resulting measure is expressed as db(A), because the weighting curve A (according to some international standard) has been used, which is optimized for this purpose.

Note that DAC background noise is typically measured unweighted, which is one of several reasons why you can't directly derive an audibility estimate.

Other obstacles lie in the fact that there is additional gear between the DAC and the ear, which has its influence. The DAC output, at the very minimum, has to be amplified, and fed to a loudspeaker, where the electrical signal gets converted into sound. How the DACs dynamic range in dB translates into db(SPL) depends on the gear in between, including the listening room with the positioning of speakers and listener.

So, as a simple example, any DACs background noise becomes audible if you crank up the volume knob of the amplifier far enough, or if you get your ear to the speaker close enough.

Hence, dynamic range in this situation only makes sense as a relative measure between the loudest possible sine wave and the loudness of the background noise, given a fixed setting of the system. You need to specify this explicitly, because there isn't a standardised or self-evident setting to work from.

Any tests show audible noise floor?

Reply #21 –
Quote from: augustine on
Have their been any tests to show the audible noise floor of Dacs ? Ie when can we hear the noise -55 db ? Etc etc
What were the results ?


The Fletcher Munson curves have been well  known to show the SPL threshold of audible audible tones for about 80 years. Google is your friend.

A signal level given as -xxx dB cannot be directly related to the Fletecher Munson curves because it is a not a SPL.

Any tests show audible noise floor?

Reply #22 –
Quote from: augustine on
(generally quoted as 0 db - 160 db but point being there is a "quietest" people can here as well as a "most high pitched" etc etc)

160 dBSPL.  Are you kidding?!?

Any tests show audible noise floor?

Reply #23 –
Quote from: Arnold B. Krueger on
Quote from: augustine on
Have their been any tests to show the audible noise floor of Dacs ? Ie when can we hear the noise -55 db ? Etc etc
What were the results ?


Fletcher Munson curves have been well  known to show the SPL threshold of audible audible tones for about 80 years. Google is your friend.

A signal level given as -xxx dB cannot be directly related to the Fletecher Munson curves because it is a not a SPL.


I believe we've discussed the Fletcher  munson curves before Arnold.
In that case how was a previous poster able to assure me that the noise floor was audible just by looking at the specs (in a test I believe you were involved with the ada8000 ? )
I think this is where I was getting confused - with the different reference points and scales used with db dbr dbv dbu etc etc. However there must be a way of measuring whether the loudness  (spl) of the noisfloor coming out of a device (say at 1m with the gain set in the 0 db or 4 db ) is audible in relation to Fletcher Munson etc (I appreciate it's frequency dependant ).of course I could just turn the bloody thing on and ask if anyone can hear a hiss (;

Any tests show audible noise floor?

Reply #24 –
When talking about high SPL consider the NIOSH recommendation of max ~1h exposure to 94 dB SPL. Every +3 dB halves this time (e.g. 100 dB SPL => 15 minutes), after which permanent damage can occur.
"I hear it when I see it."