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Audibility thresholds of amp and DAC measurements
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Simply compare noise floor of a quiet listening room with peak level available from a standard good loudspeaker. Not rocket science.
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Bachatero heard a low level tone. Very doable. Then it seemed to me jimster480 was conflating that with the ability to hear -85 db distortion. Maybe I misread it. One reason I don't like SINAD or its flipside THD+N. Keep the N and THD separate. At a minimum I was very clear in my reply where I said -80 db distortion.
abm0
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Also, tones as high as 28 kHz. Highest number I've seen reported so far.
Hearing thresholds for pure tones above 16kHz
Hearing thresholds for pure tones between 16 and 30kHz were measured by an adaptive method. The maximum presentation level at the entrance of the outer ear was
pubs.aip.org
Also, tones as high as 28 kHz. Highest number I've seen reported so far.
Hearing thresholds for pure tones above 16kHz
Hearing thresholds for pure tones between 16 and 30kHz were measured by an adaptive method. The maximum presentation level at the entrance of the outer ear was
The question I have is "what level"? Skin sensation for ultrasonics at high levels is old news, but it's not "hearing" per se.
Also, at 99dB SPL the air isn't linear any more. Doesn't matter what frequency, there will be subharmonics, harmonics, and all sorts of other nonlinearities.
ChatGPT answered:
Nonlinearity Threshold for 20 kHz and 30 kHz
- The threshold for 1% distortion scales inversely with frequency because waveform steepening occurs faster for shorter wavelengths.
- At 20 kHz, the SPL threshold for 1% distortion is typically around 145–150 dB SPL.
- At 30 kHz, it is slightly lower, approximately 140–145 dB SPL.
Also, don't forget distance attenuation. The listening distance was 0.5 m. The sound pressure at the transducer membrane surface could easily be 30+ dB higher than at the listening distance and went nonlinear there.
Not an error, a misunderstanding. 1% distortion is -40dB A subharmonic resulting from a 25kHz tone at 90 dB that's in the ear canal resonance range can be audible at 10dB SPL. That's 80dB, not 40dB. At 140dB SPL that's 100dB SPL for the subharmonic. That's earsplitting itself.
NOW, most of the problem will be in harmonics, not subharmonics, so it's not as bad as that, *but* it is important to be careful with the spectrum of the added distortion. Subharmonics are weird in that it's hard as(*&( to figure out exactly where they might land.
They weren't using a compression driver, were then? I'm not handy to read the paper right now, but distortion in compression driver throats is often epic.
Also, remember that distortion does not START at the level you gave above, it reaches 1% there. Much less than 1% can still lead to surprising artifacts.
Also, remember that distortion does not START at the level you gave above, it reaches 1% there. Much less than 1% can still lead to surprising artifacts.
Hmmm. I have questions, but not directed to you, sorry.
Snafu
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Amplifiers have this power vs distortion graph for different frequencies. When dac has volume control, is similar graph measurable ?
Or when measuring max out can we measure distortion for different frequencies and is it in audible level? Thanks
Or when measuring max out can we measure distortion for different frequencies and is it in audible level? Thanks
Step one. Is the DAC volume control digital or analog? If it's modifying level before the DAC, say like windows level settings for the most part, you will see the noise floor of the dac seem to rise as level goes down.Amplifiers have this power vs distortion graph for different frequencies. When dac has volume control, is similar graph measurable ?
Or when measuring max out can we measure distortion for different frequencies and is it in audible level? Thanks
If the gain is analog, it's not entirely clear. There will be a noise floor due to the DAC, and an overload point due to the DAC. Then there will be the other noise due to the analog outputs. This can interact in a number of ways, usually not completely strange, but if the analog section is really good for a 16 bit DAC, you may scale the DAC noise level up and down without the analog system interferring. The question is "where does the gain control change the sytem gain" and "what is the analog noise floor" and "how much distortion is there".
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Without discussing the founding of all your figures this one is obviously wrong.
IMD SMPTE is measured in relation to the -12dB high frequency component.
Therefore, it makes sense to lower your thresholds accordingly.
Refering to this image:
There are only two vertical lines (orange and green).
Should JND be considered at levels of ~0.2 ~ 0.5 dB? Those will be horizontal lines.
It's unlikely human will be able to hear non-linearity at less than 0.2 dB.
If JND of 0.2 dB is considered (blue lines), then this DAC has made a very good job keeping audible linearity up to -115 dBFS
There are only two vertical lines (orange and green).
Should JND be considered at levels of ~0.2 ~ 0.5 dB? Those will be horizontal lines.
It's unlikely human will be able to hear non-linearity at less than 0.2 dB.
If JND of 0.2 dB is considered (blue lines), then this DAC has made a very good job keeping audible linearity up to -115 dBFS
I'm not entirely sure of what you're plotting there. This is obviously not snr, so can you explain what are are measuring? You say "relative level" which would suggest you're measuring input vs. output level, yes? Across what frequency range?Refering to this image:
There are only two vertical lines (orange and green).
Should JND be considered at levels of ~0.2 ~ 0.5 dB? Those will be horizontal lines.
It's unlikely human will be able to hear non-linearity at less than 0.2 dB.
If JND of 0.2 dB is considered (blue lines), then this DAC has made a very good job keeping audible linearity up to -115 dBFS
View attachment 438516
Jimster480
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Personally I think this is trash linearity. To me this is the most important measurement of them all and this DAC fails it completely. It should be 0.2db or less to 20 bits, there are plenty of competent products which can do this.Refering to this image:
There are only two vertical lines (orange and green).
Should JND be considered at levels of ~0.2 ~ 0.5 dB? Those will be horizontal lines.
It's unlikely human will be able to hear non-linearity at less than 0.2 dB.
If JND of 0.2 dB is considered (blue lines), then this DAC has made a very good job keeping audible linearity up to -115 dBFS
View attachment 438516
Amir does these tests of DACs.
X axis is the gozinta, and Y axis is the gozouta. Relative in terms of relationship to input at very low levels. Measured tone seems to be 1kHz, bandwidth unstated in anything I can find but it apparently catches the effect of band pass filters so probably at least 40 kHz.
Rick “this is something Amir provides” Denney
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