Audibility thresholds of amp and DAC measurements

[j_j]

Hi @j_j
Apparently the quietest anechoic chamber is at Microsoft and it was measured at -20 dB(A) SPL. Do you know how to correctly interpret and compare those numbers?
(I guess maybe A-weighting can account for some of the difference)

They estimate the EXCESS NOISE by subtracting the "atmospheric noise". Yeah, that's kind of hinky. The atmospheric noise will be there at 1 atmosphere pressure. Always.

I'm quite aware of how the room is spec'ed and built. There's no magic, it's a way to make impressive numbers. Weighting would have some effects, but they can calculate the actual noise floor, and then they measure how much above the noise floor the room is, and subtract the thermal noise floor to find the excess noise.

Also, of course, if you measure in any one ERB, you'll get a smaller number. That would also be, well, true but misleading.

 

[DonH56]

<elided>
Again, tonal vs. narrow-band-noise is not very different, but yes, you can, at your ear canal resonance, get into small negative SPL's, but only if you're young and your organ of corti is un-blasted-to-bits.

Well, crud, I lose on both counts...

 

[j_j]

Well, crud, I lose on both counts...

Yeah, welcome to the modern world, where the noise level on the street exceeds the normal indoor talking level. Yeah, I measure that s**t.

 

[NTK]

This may be a little off topic. I had been looking for this Auditory Demonstration CD by the Institute for Perception Research (IPO) at Eindhoven University of Technology (TU/e), Northern Illinois University, supported by the Acoustical Society of America.

Auditory demonstrations on compact disc

In 1984, the Committee on Education in Acoustics of the ASA discussed the possibility of reissuing the “Harvard Tapes,” a series of audio demonstrations on tape

pubs.aip.org

I finally found it at the TU/e site. Free download!

Auditory demonstrations

research.tue.nl

 

[Hayabusa]

So is narrow-frequency noise. You do understand that the 6dB is white noise, across 20-20K, yes? So the energy in any 1 ERB is much smaller.

I would suggest you go watch through my "hearing tutorial" at www.aes.org/sections/pnw in the "meeting recaps" area. This may help you to realize you just compared an apple to a grapefruit.

nothing wrong with that, in this case we ARE comparing apples and grapefruits. Wideband noise and tonal information. A 6dB SPL white noise level suggest for others maybe that that's the absolute lower limit, but its not. That's why I made my statement. Maybe someone else found it useful.

 

[abm0]

at your ear canal resonance, get into small negative SPL's, but only if you're young and your organ of corti is un-blasted-to-bits.

Hmm, Wikipedia gives me "The threshold of hearing is frequency-dependent and it has been shown that the ear's sensitivity is best at frequencies between 2 kHz and 5 kHz, where the threshold reaches as low as −9 dB SPL." after I tried one of those geepeetees and it answered something completely stupid that was positive numbers in dB.

But anyway this should all be made irrelevant by environmental noise anyway. The lowest I've measured with some old-school indicator needle second-hand sound level meter (of admittedly unknown calibration) in my residential-area apartment in the dead of night was 20 dBA, so I should probably demand no better than about 10 dBA of unwanted content out of my reproduction chain since that adds up to no more than 20.4 or so dBA and should be just below the threshold of being able to detect a difference vs. pure environmental noise.

 

[Blumlein 88]

Hmm, Wikipedia gives me "The threshold of hearing is frequency-dependent and it has been shown that the ear's sensitivity is best at frequencies between 2 kHz and 5 kHz, where the threshold reaches as low as −9 dB SPL." after I tried one of those geepeetees and it answered something completely stupid that was positive numbers in dB.

But anyway this should all be made irrelevant by environmental noise anyway. The lowest I've measured with some old-school indicator needle second-hand sound level meter (of admittedly unknown calibration) in my residential-area apartment in the dead of night was 20 dBA, so I should probably demand no better than about 10 dBA of unwanted content out of my reproduction chain since that adds up to no more than 20.4 or so dBA and should be just below the threshold of being able to detect a difference vs. pure environmental noise.

Devil in the details. That single number is presumably 20hz to 20 khz. Most environmental noise is pinkish to brownish. Most of the noise energy is in the lower frequencies. So even with a measured 20 dbA, in that 2-5 khz range it might be 10 dbA or even close to 0 dbA. One way to model this is ERBs or effective rectangular bandwidth. Your ear kind of divides up parts of the bandwidth which allows it to hear a bit below the overall noise level. This is simplified as your ear can shift these bands up and down around what it hears. Roughly into maybe 30 bands. So the noise level meter might be 20 dbA, but in the few bands around that 2-5 khz range it might only be a few db or close to zero db SPL and your ear even in that noise could hear things in that range at that level.

This might lead one to hear lower level noise than you anticipate, but on the other hand with music playing it probably masks it pretty completely. If you've ever heard an LP, you can hear some of the surface noise of the vinyl LP fairly easy in the lead in grooves or silent grooves between tracks, but when the music starts you cannot hear it.

 

[Hayabusa]

Devil in the details. That single number is presumably 20hz to 20 khz. Most environmental noise is pinkish to brownish. Most of the noise energy is in the lower frequencies. So even with a measured 20 dbA, in that 2-5 khz range it might be 10 dbA or even close to 0 dbA. One way to model this is ERBs or effective rectangular bandwidth. Your ear kind of divides up parts of the bandwidth which allows it to hear a bit below the overall noise level. This is simplified as your ear can shift these bands up and down around what it hears. Roughly into maybe 30 bands. So the noise level meter might be 20 dbA, but in the few bands around that 2-5 khz range it might only be a few db or close to zero db SPL and your ear even in that noise could hear things in that range at that level.

This might lead one to hear lower level noise than you anticipate, but on the other hand with music playing it probably masks it pretty completely. If you've ever heard an LP, you can hear some of the surface noise of the vinyl LP fairly easy in the lead in grooves or silent grooves between tracks, but when the music starts you cannot hear it.

Don't forget the ears ability to hear constant tones well below the noise level also.

 

[abm0]

you can hear some of the surface noise of the vinyl LP fairly easy in the lead in grooves or silent grooves between tracks, but when the music starts you cannot hear it.

Eehhh let's just say for the purpose of buying an "endgame" DAC-amp I will choose to not rely on masking. A lot of discussion on this topic treats music as always always busy stuff with heaps of active frequencies but I listen to pretty chill stuff, a lot of it electronic, and encounter far more minimalistic sections than, say, a classical or jazz aficionado would. Pure-tone analysis is more relevant to me and masking less relevant.

 

[j_j]

Hmm, Wikipedia gives me "The threshold of hearing is frequency-dependent and it has been shown that the ear's sensitivity is best at frequencies between 2 kHz and 5 kHz, where the threshold reaches as low as −9 dB SPL." after I tried one of those geepeetees and it answered something completely stupid that was positive numbers in dB.

But anyway this should all be made irrelevant by environmental noise anyway. The lowest I've measured with some old-school indicator needle second-hand sound level meter (of admittedly unknown calibration) in my residential-area apartment in the dead of night was 20 dBA, so I should probably demand no better than about 10 dBA of unwanted content out of my reproduction chain since that adds up to no more than 20.4 or so dBA and should be just below the threshold of being able to detect a difference vs. pure environmental noise.

Well, that's why I mentioned the ear canal resonance, which is usually the ERB with the highest sensitivity. Of course it's frequency dependent.

There are basic physics issues, in particular having standard air on both sides of the eardrum at STP means you have something in the 6 to 8.5 dB SPL white noise present due to the existence of the actual atmosphere.

Since the ear is very frequency sensitive, you can't hear that. Barely. At the ear's most sensitive point, a person in a quiet place can ALMOST hear that. Those of us in their 70's, not so much.