Distortion down to -300 dB, what exactly does that mean physically?

[BrEpBrEpBrEpBrEp]

Check out Sir Watts' new book "The Depth Getting Deeper - My Life With Synesthesia -"

here is a quote from the book "... and I'm looking at the numbers on my screen... -330dB, -350dB... and I can't believe it... I can hear that!"

LMAO talk about telling on yourself, eh? Looking at the numbers on his screen...

 

[voodooless]

I think the discussion misses Rob Watts' actual claim. He implies that he achieved 64bit linearity, through processing, for some undefined range of values (he mentioned a -90dB signal specifically but no level) to within -350dB.

So here's the Chord DAVE:

• https://chordelectronics.co.uk/product/dave/
• https://www.stereophile.com/content/chord-electronics-dave-da-processor-measurements

Say it outputs 4Vrms. -90dB down would be 0.000127V or 127 microvolts. So he is able to output 127uV to within 4e-22V (-350dB) of accuracy (0.0000000000000000000004V).

Watts says (paraphrasing): This is why ethernet cables make a difference... because they reduce RF noise modulation, which makes that level of accuracy possible. Something like that.

Did I mess this up?

Don't know if you messed it up. Even if true it total nonsense. Sure digitally he might be able to achieve this precision, but not in the analogue domain, and Amir's reviews prove this, and I think me as well with my example in the first post: it would mean that you have to control the stream of electrons as good as less than 1 electron per second. Roughly.. but even if orders of magnitude off, it still ridiculous.

 

[Sir Sanders Zingmore]

If you can hear -522 dB, Rob Watts will probably give you a job if you ask him.

i just asked him. Do you think he’ll hear me from Australia?

 

[peterzuid]

I'm not sure that you're really seeing how little -300 dB is here. That's not a "minor difference". That's a difference in sound level that functionally cannot exist in air on Earth - and it's not even close.

Interaural level differences aren't even close - play a sound on a speaker, turn your head sideways, and measure the SPL on the near and far sides of it. A quick search says that it would be at most ~20 dB at high frequencies, and functionally nothing at low frequencies where time difference matters more.

Please do not confuse dB absolute sound levels with distortion levels. dB is meant as a ratio and it will have no problem to exist in air. On the contrary; we can be sure they are there from a physical point of view.

 

[peterzuid]

As some of you guys might know, the famous Rob Watts has mentioned on more than one occasion that he can hear and measure distortion down to -300 dB. Cited by @amirm here for instance. He also says something similar in this video:

Staring at roughly the 17min mark.

Now I was thinking about a thought experiment that you guys can probably help me with, especially the physics nuts. I'd like to explore what this actually would mean on a physical level? So how little is the voltage change? How many electrons would that actually need? And if we're talking, what about air pressure difference? But you guys can come up with other stuff. Probably the infamous shoutometer will come up, which I find rather uninteresting because it just not model the practical world very well.

So I had a crack at voltage. So let's see how small of a voltage difference -300 dBV is. Well, I had to resort to Wolfram Alpha because my go-to calculator gave me just zero So Wolfram was more helpful and gives 1*10^-15, which is 1 fV RMS (so femtovolt). To count electrons, we need to add some assumptions: we need current. So let's assume it's a DAC, and it's syncing into 20K input impedance of a pre. Now we can calculate the number of electrons needed for this 1 fV voltage. So 1A has 6.24 quintillion electrons (10^18). So, how many electrons does out -300dbV signal have into 20k? Well, it's not even 1 electron per second: it's 0.312 Already feeling silly Rob?

Hope you guys can fact check me on this. Would be fun to do the same for the air pressure difference.. Once again my go-to calc gives 0

Completely agree with this calculation. However, in this straightforward static calculation you forgot the most important; the time domain. Maybe you could redo the calculation with this in account ?

 

[BrEpBrEpBrEpBrEp]

Please do not confuse dB absolute sound levels with distortion levels. dB is meant as a ratio and it will have no problem to exist in air. On the contrary; we can be sure they are there from a physical point of view.

My post you're replying to was referring to -300 dB relative to a reference, i.e. 300 dB below the level of whatever reference signal.

If you look at my other posts in this thread, you'll see that I understand what a decibel is just fine and that I've already made the case that a noiseless dynamic range of more than ~214 dB is physically impossible on Earth.

Quietest room on the planet is -20 dB SPL. Loudest possible sound in air is 194 dB SPL. 194 - -20 = 214 dB maximum dynamic range in the quietest room on the planet.

So, choosing the loudest possible sound as 0 dB, -300 dB is indeed well beyond impossible to perceive on this planet.

 

[audio2design]

As some of you guys might know, the famous Rob Watts has mentioned on more than one occasion that he can hear and measure distortion down to -300 dB. Cited by @amirm here for instance. He also says something similar in this video:

This reminds me of a Dilbert cartoon. A lot of things remind me of Dilbert Cartoons:

It was something about mind altering drugs.

I think the bigger question is, was this the most ridiculous thing he said in that presentation.

 

[peterzuid]

My post you're replying to was referring to -300 dB relative to a reference, i.e. 300 dB below the level of whatever reference signal.

If you look at my other posts in this thread, you'll see that I understand what a decibel is just fine and that I've already made the case that a noiseless dynamic range of more than ~214 dB is physically impossible on Earth.

Quietest room on the planet is -20 dB SPL. Loudest possible sound in air is 194 dB SPL. 194 - -20 = 214 dB SPL maximum dynamic range in the quietest room on the planet.

So, choosing the loudest possible sound as 0 dB, -300 dB is indeed well beyond impossible to perceive on this planet.

It seems I left you confused.........then better forget the remark

 

[BrEpBrEpBrEpBrEp]

It seems I left you confused.........then better forget the remark

I'm not sure that I'm the one that's confused here. Regardless, the assertion that two sounds with 300 dB amplitude difference can be perceived in air on earth is demonstrably incorrect (even if you can hear sounds slightly below the noise floor of a room, before someone brings that up). Average human threshold of hearing is 0 dB SPL anyways.

 

[peterzuid]

This reminds me of a Dilbert cartoon. A lot of things remind me of Dilbert Cartoons:

It was something about mind altering drugs.

Like the Dilbert also. I am a fan of Dilbert, the manager but also Woody. Which one do you like the most ?

 

[danadam]

Quietest room on the planet is -20 dB SPL. Loudest possible sound in air is 194 dB SPL. 194 - -20 = 214 dB SPL

On technical note, that last SPL should not be there. Just dB.

 

[peterzuid]

Average human threshold of hearing is 0 dB SPL anyways.

I try once again........ do not confuse absolute sound levels with .............I will leave it here!

 

[BrEpBrEpBrEpBrEp]

On technical note, that last SPL should not be there. Just dB.

Whoops, my bad, typo. Thanks!

 

[BrEpBrEpBrEpBrEp]

I try once again........ do not confuse absolute sound levels with .............I will leave it here!

The average human cannot hear below 0 dB SPL. Maximum SPL in air is 194 dB SPL, which is likely to kill. Therefore, the average human cannot perceive level differences (relative) above 194 dB.

 

[audio2design]

Bob can. Bob can hear everything.

 

[pozz]

The average human cannot hear below 0 dB SPL. Maximum SPL in air is 194 dB SPL, which is likely to kill. Therefore, the average human cannot perceive level differences (relative) above 194 dB.

0dB SPL is the threshold for 1kHz. The "average" person can hear negative SPL in 2-6kHz range.

 

[BrEpBrEpBrEpBrEp]

0dB SPL is the threshold for 1kHz. The "average" person can hear negative SPL in 2-6kHz range.

Ahh right, thanks! Equal-loudness curve says maybe ~-8 dB SPL. I'm sure some can hear quieter too, but certainly not by 100 dB.

https://upload.wikimedia.org/wikipedia/commons/thumb/4/47/Lindos1.svg/1141px-Lindos1.svg.png

One fun thing is the SPL in air has a lower limit due to thermal motion of the air itself, somewhere between -20 and -30 dB SPL.

https://physics.stackexchange.com/questions/110540/how-loud-is-the-thermal-motion-of-air-molecules

 

[BrEpBrEpBrEpBrEp]

Bob can. Bob can hear everything.

Bob can hear us talking shit, and he's coming for us all...

 

[Colin James Wonfor]

I wonder if he can detect thermal noise at Absolute Zero -270C ish or shhhhh .

 

[JohnA]

Good point, the 300+ db refer to Verilog simulations.

Shouldn't such simulations account for thermal noise?