What is the "just noticeable difference" in audio loudness?

rbbert

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In references I could find with a quick Google search, the JND for audio loudness is listed as 1 dB. That may well be the level for an obvious JND, but it's hardly the JND for careful listening, which is clearly much less (I would guess somewhere between 0.1 and 0.5 dB). It also is probably different depending on the type of signal (pure tone, white or pink noise, etc.) and whether or not the volume change is applied to the entire frequency range of the signal. I would welcome more information and comments.
 

DaveC

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Depends on SPLs too, at high SPL an increase of 1 dB can seem like a lot, at low SPL it doesn't seem as much due to our ear's sensitivities.
 

amirm

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The question has a complex answer as it depends on a lot. Best research I have seen is the AES paper, The Subjective Loudness of Typical Program Material, http://www.aes.org/e-lib/browse.cfm?elib=12350

I plan to summarize its findings at Audio Science Review but for now, here is a key graph that tells most of the story:

 

Speedskater

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Time would be a very big factor. With instantaneous switching, it might be a small fraction of a dB. But just 10 seconds of silence will desensitize the listener.
 

rbbert

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Time would be a very big factor. With instantaneous switching, it might be a small fraction of a dB. But just 10 seconds of silence will desensitize the listener.
Yes, this part of what I'm getting at; 1 dB may well be the JND in this case, i.e. after desensitization. Good and useful responses so far, all of which makes me wonder why 1 dB is till being used in most references as the JND, when in fact it is not.
 

amirm

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The few times I have seen someone provide a reference for this, it has been from Clark's ABX paper where he shows this 1 db JND for mid frequencies:



This however is not a good reference as Clark's work was casual and not exhaustive.
 

rbbert

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Nevertheless, it suggests that for sound with wide frequency content, the JND is closer to 0.1 than 1.0 dB. But his experiment wasn't really designed to define the JND, and as you say the experimental methods weren't rigorous.
 

Robh3606

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FWIW Harman can level match to .03db in their test lab

Rob:)
 

thedudeabides

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Based on my past experiences with CJ preamps, the volume is adjustable in 0.7db increments. Very audible but not too bad from a user perspective.

0.1 db increments would be ideal but you run into the tech challenge of the volume control being up to the task from a signal to noise ratio. Preamps that do this gradation well, while maintaining complete transparency, are difficult to find and tend to be quite pricey IMHO.
 

Avidlistener

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When I'm mixing audio for video production in my genelec 8020 desktop system I can hear a half dB change at moderate levels in the near field.
Haven't tried the test on my main system in a big room.
 

Gregadd

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I came across a graph that suggest that for 50 hz v 1000hz discrimination is 10 dB for loud sounds. It's 20 decibels for midramge sounds and 40 decibels for very soft sounds.
 

FrantzM

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Interesting debate...I always assumed, wrongly I must admit, that 1 dB was the threshold ... I doubt however that a .7 dB change in volume level would be "very" audible... I am not debating the audibility of such simply that it would be "very" easy :)
It is getting clear to me however that the process of level matching is not as simple as it sounds ..pun intended... A new twist on the debate about audibility...
 
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audioguy

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Interesting debate...I always assumed, wrongly I must admit that 1 dB was the threshold ... I doubt however that a .7dB chnagein volume level would be "very" audible... I am not debating the audibility of such simply that it would be "very" easy :)
It is gteting clear to me however that the process of level matching is not as simple as it seems ... A new twist on the debate about audibility...

Level matching is quite easy if you run a full frequency sweep through the two devices that are being compared and then use something like REW to measure and and overlay the two responses until they match EXACTLY. They are then level matched.

When I was comparing two SSP's this way, we could detect 1/2 db difference (and it ALWAYS sounded better).
 

esldude

New Member
In references I could find with a quick Google search, the JND for audio loudness is listed as 1 dB. That may well be the level for an obvious JND, but it's hardly the JND for careful listening, which is clearly much less (I would guess somewhere between 0.1 and 0.5 dB). It also is probably different depending on the type of signal (pure tone, white or pink noise, etc.) and whether or not the volume change is applied to the entire frequency range of the signal. I would welcome more information and comments.

I think there is an issue being confused here.

Just noticeable difference, typically quoted as 1 db, but yes frequency and loudness dependent can vary between maybe .6 db to 1.3 db.

However, listening tests can be corrupted if levels are not matched to within .1 db. The confusion is these .2, .3, .4 db differences would not be noticed. They are enough to corrupt a comparison though no one would hear a loudness difference. They hear a quality difference not suspected to be a loudness difference. At somewhere around 1 db depending on particulars someone would notice and say, "hey that sounds a little louder than this other thing over here".

Now sometimes with complex music you might be talking near 3 db before people start noticing one is louder than the other with real reliability especially if switching isn't done quickly between two sources at different levels.
 

jkeny

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I think there is an issue being confused here.

Just noticeable difference, typically quoted as 1 db, but yes frequency and loudness dependent can vary between maybe .6 db to 1.3 db.

However, listening tests can be corrupted if levels are not matched to within .1 db. The confusion is these .2, .3, .4 db differences would not be noticed. They are enough to corrupt a comparison though no one would hear a loudness difference. They hear a quality difference not suspected to be a loudness difference. At somewhere around 1 db depending on particulars someone would notice and say, "hey that sounds a little louder than this other thing over here".

Now sometimes with complex music you might be talking near 3 db before people start noticing one is louder than the other with real reliability especially if switching isn't done quickly between two sources at different levels.

I don't disagree with this i.e. that established JNDs are not sacrosanct & only define limits within certain strict conditions of listening.
However, do you have any blind listening test examples which demonstrate that .1dB is the JND measure that is discernible as a quality difference when listening to music?

Furthermore, is this 0.1dB match needed at all frequencies or what is the needed amplitude/frequency match between two waveforms which will guarantee no quality difference will be audible i.e. it's 0.1dB at some frequencies (what frequencies) but 0.6dB or 1.3dB at other frequencies (again what frequencies)?
 
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rbbert

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It's not scientific (which is why I opened this topic, to try to learn more), but like other posters I routinely notice a 0.5 dB difference when listening to music, either working in a DAW with 'phones or just using the volume control on one of my systems. That difference is so easily noticed after awhile that I wondered why 1 dB is so commonly mentioned as the JND.
 

jkeny

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It's not scientific (which is why I opened this topic, to try to learn more), but like other posters I routinely notice a 0.5 dB difference when listening to music, either working in a DAW with 'phones or just using the volume control on one of my systems. That difference is so easily noticed after awhile that I wondered why 1 dB is so commonly mentioned as the JND.

Sure, I too would like to learn more about this subject & I think that distinguishing between the measure of intensity that instruments use & the loudness that our auditory perception perceives is an important distinction & would explain why we have frequency-dependent differences in sensitivity to intensity.

In other words, it's educational to understand the mechanism whereby the amplitude is processed by our auditory system into loudness. JJ Johnston states this about the mechanical side of loudness perception in the article I referenced:
"Regarding that complex relationship between loudness and intensity, Johnston reviewed a few essential points:

- When the frequency content of a signal is unchanged, loudness is approximately proportional to the 1/3.5 power of the signal power, or the 1/1.75 power of amplitude.
- The ear has a mechanical filtering system that splits the signal into "critical bands" or "ERBs (Effective Rectangular Bandwidth)."
- Signals in the same critical band convert intensity to loudness with approximately the power law relationship stated above.
- Signals in different bands add linearly in loudness."[/UL]

There's an interesting prediction from this explanation & that is that we have a different sensitivity to noise than to tones. Why? Because noise, tending to be broader band in nature than pure tones, span more ERBs & therefore "Signals in different bands add linearly in loudness"

Does this prediction hold up in practise? Yes, in the form of the little known ITU-R 468 loudness curves for noise which are different to the Fletcher-Munson equal loudness curves
 

jkeny

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I found an article that addresses this question specifically here

In it a chart of research results over 60 years is given & the lowest JND is 0.25dB F.E. Toole and S. Olive, "The Modification of Timbre by Resonances: Perception and Measurements", JAES vol 36, # 3, March 1988, pp 122-142

The author states "Toole and Olive, on the other hand, in their 1988 study used pink noise for their acoustic signal source and determined that a 5 kHz resonance, with Q = 1 was just detectable at .25 dB." But later "The .25 dB figure quoted from the Toole & Olive research seems to contradict this (his JND of 0.75dB or 1dB), but consider the filter Q = 1. That's a pretty broad chunk of the audible spectrum over which that resonance exists. With the ear-brain combo performing an integration across that broad a portion of the audible spectrum than its easy to see how a large amount of acoustical energy is captured, leaving a change that small noticeable. However, pink noise is not real world and one thing my research has shown is that the hearing process reacts very differently to different types of sound; a .25 dB detectable difference using real music just isn't plausible and the research supports that."

He goes on to state "In this particular article, I settled on a minimum discernable difference dB value of .75 - 1.0. My experience has shown that this is what the average listener, under average listening conditions, listening to music played back through typical consumer-grade audio gear will be able to clearly identify - and do so repeatedly."

So, I'm still looking for any research which backs up the claim that 0.1dB amplitude difference is noticeable as a quality difference when playing music? Any links, ESL?
 

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