Audibility of total harmonic distortion: A test

[Vineethkumar01]

Hi all,
I found this distortion test on ASR recently. I found it very interesting:

It basically helps us understand at what level of THD each of us, through our audio systems, are able to audibly make out total harmonic distortion.
My personal score as per this video (on my cheap 600Rs edifier earphones) is as follows:

Music: around 11% THD
Tone at 500 Hz: around 5%
Tone at 100 Hz: around 11%

Please test and post your results..

 

[raghupb]

Thanks for the link @Vineethkumar01
Very interesting experiment to undertake on one'e ears.

My score (using Samsung mobile's AKG earplugs, with out my hearing aids, obviously)
Music: ~15%
500 Hz: ~5%
100 Hz: ~8%

Guess, my ears are more sympathetic to music
Will try again sometime on the speaker system (with and without hearing aid)

Cheers,
Raghu

 

[Vineethkumar01]

@raghupb: Awesome
Let's try to put some numbers to our obsession about audio..

 

[raghupb]

So the whole THD of 0.001% can safely be thrown out my window, at least
I have a tube preamp and a H2 profile power amp (I think); so they are "effect boxes"
I don't seem to have a pair of ears to discern low/high distortion behavior.
But definitely do have a pair of ears that like harmonic "effects"

Cheers,
Raghu

 

[Vineethkumar01]

Now I think it would have been nice if we had a test for intermodulation distortion also.
Just to identify how much more it can be easily identified compared to harmonic distortion.

 

[Decadent_Spectre]

Hi Vineeth, you may find this post useful -

Best tracks to test stereo imaging, tonal balance and dynamics

https://www.marantz.com/en-za/blog/bloglisting/best-tracks-to-test-stereo-imaging-tonal-balance-and-dynamics

www.hifivision.com

The second is a Klippel test so it should hold some weight.

 

[Vineethkumar01]

So the whole THD of 0.001% can safely be thrown out my window, at least
I have a tube preamp and a H2 profile power amp (I think); so they are "effect boxes"
I don't seem to have a pair of ears to discern low/high distortion behavior.
But definitely do have a pair of ears that like harmonic "effects"

Cheers,
Raghu

Also, if we look at the distortion profile in that video, let's say the 100Hz tone test. We can see from the graph that with rising distortion, we are more sensitive to high order harmonic distortion than lower order (looking at the lower and lower amplitudes of the higher order distortion components).
It would have been nicer if we had a separate test for even order harmonic distortion and odd order harmonic distortion components. Because I suspect we are identifying that the odd order harmonic distortion which is making us aware about overall distortion (clipping like sound).

 

[raghupb]

Also, if we look at the distortion profile in that video, let's say the 100Hz tone test. We can see from the graph that with rising distortion, we are more sensitive to high order harmonic distortion than lower order (looking at the lower and lower amplitudes of the higher order distortion components).
It would have been nicer if we had a separate test for even order harmonic distortion and odd order harmonic distortion components. Because I suspect we are identifying that the odd order harmonic distortion which is making us aware about overall distortion (clipping like sound).

Odd harmonics add up, right? So they can gang up and make us realize something is off.
Cheers,
Raghu

 

[Vineethkumar01]

Hi Vineeth, you may find this post useful -

Best tracks to test stereo imaging, tonal balance and dynamics

https://www.marantz.com/en-za/blog/bloglisting/best-tracks-to-test-stereo-imaging-tonal-balance-and-dynamics

www.hifivision.com

The second is a Klippel test so it should hold some weight.

Awesome.. Thanks @Decadent_Spectre. I will definitely go through every one of them...

 

[drkrack]

Music Around 10%
Pure Tones 3 & 5 % Respectively.

So the whole THD of 0.001% can safely be thrown out my window, at least

absolutely, but many a times you just don't make out the distortion distinctively; but instead you feel that something is not right (Not able to pinpoint what it is ) . Nevertheless, 0.01% shouldn't matter.

 

[Vineethkumar01]

Odd harmonics add up, right? So they can gang up and make us realize something is off.
Cheers,
Raghu

Yes.
Both even and odd order distortion components add up to the original signal once harmonic distortion happens.
For example, In the video, for the 100Hz tone test, originally there is a single peak at 100 Hz. Once we see distortion introduced in the spectrum plot (peaks starting to pop up in the graph at 200 Hz, 300Hz, 400Hz and so on), it means sine wave of frequencies 200 Hz, 300 Hz (integer multiples of the fundamental of 100 Hz) etc are adding up with our original tone of 100 Hz. But we can see that the amplitude of the 200 Hz, 400Hz, 600 Hz (even order components) are higher than the adjacent odd order components (300Hz, 500 Hz, 700 Hz etc).

 

[mbhangui]

Blind test using macbook pro 3.5mm out to a AKG headphone. I used the space bar key to pause music as soon as I felt the distortion. Did it multiple times
Music around 2 %, extremely audible from 3% onwards
500 Hz around .07 % extremely audible from 0.1 % onwards
100 Hz around 0.8% extremely audible from 1% onwards

 

[mbhangui]

There is another test that @Decadent_Spectre had put up a link in another post. This is the klippel test for distortion audibility thresholds

Listening Test

www.klippel.de

I got a threshold of -51 dB for distortion which was reached with a allo class d amp connected to my electrostatic speaker. Using a Class A valve amp, I did poorly at around -21 dB. The funny thing is that people enjoy these distorted class A valve amps. I definitely need to do the tests again, but each test involves around an hour or so to complete

You reached an audibility threshold of -51 dB. This value is -29 dB below the mean value of the audibility threshold of all listeners participated in the test. Apparently, you have been very sensitive in detecting signal distortion. You may be a trained listener and have sufficient experience in assessing sound quality, or you are just lucky by getting this good result on accident.

 

[chander]

MacBook Air - USB C - 3.5mm apple dongle - Etymotic Research ER4XR.

Music - INVALID - I wish it was a different song - cause the whole song from the very beginning sounds distorted My results for music hence are not perhaps valid as I kept pausing it under 1% and once under 2% - I tried a few times - but I believe that is maybe because of the song.
500 HZ - almost immediately.
100 HZ - almost immediately.

Or perhaps it was micro-phonics of my ETYs on my T-shirt. Or perhaps I knew it was going to be distorted so my brain conjured that up. ETYs are good and so is my hearing but I am sure this is pure placebo in my case or maybe my setup is pure distortion - and test results are hence INVALID for me.

 

[ssf]

In my setup, speakers and AVR in pure direct, I could not hear distortion till above 15%. Could not run the test tracks as wife walked in. When listen to Jazz, she thinks am nuts. I did not want her catching me listening to test tones.

 

[chander]

Also anyone - what is the point of Klippel test? It keeps going on and on - I gave up after -45DB. I even got 1 wrong but there is no result.

 

[Bloom@83]

Wouldn’t time have been better spent listening to Dire Straits / Jeff Beck / Jethro Tull / <insert your choicest music > ? Just sayin we have short lives….

 

[mbhangui]

Also anyone - what is the point of Klippel test? It keeps going on and on - I gave up after -45DB. I even got 1 wrong but there is no result.

It will go on till you are able to detect very low distortion at -51 dB. There are two more levels below -45 dB. The moment you make a mistake, it will again start the tests with a higher distortion and again see the lowest threshold of distortion you can hear. Once it makes sure 3 times that you have been able to identify the distortion level it will show you the results.

If you can hear distortion at -51 dB you will be one of the 1000 people out of 26,237 people who could hear it so low.

 

[mbhangui]

In my setup, speakers and AVR in pure direct, I could not hear distortion till above 15%. Could not run the test tracks as wife walked in. When listen to Jazz, she thinks am nuts. I did not want her catching me listening to test tones.

Test tones can be classified in the 'Electronic Music' genre category.

 

[Passive_audio_enthusiast]

Hi all,
I found this distortion test on ASR recently. I found it very interesting:

It basically helps us understand at what level of THD each of us, through our audio systems, are able to audibly make out total harmonic distortion.
My personal score as per this video (on my cheap 600Rs edifier earphones) is as follows:

Music: around 11% THD
Tone at 500 Hz: around 5%
Tone at 100 Hz: around 11%

Please test and post your results..

Harmonic distortion is audible in varying percentages depending on the frequency and the loudness at which a frequency is played. So, if we look at an equipment, it’s important to know that at what frequency it’s having a particular percentage of distortion at what level of loudness.

This is exactly the reason why I mentioned kef r11 as the best possible speaker we can buy under 5 lakhs. It literally has no distortion which is audible to anyone in any frequency band.

By default when I auditioned it it didn’t wow me immediately, and ended up choosing another speaker. kef has a treble roll off and the speaker immediately found dull in comparison to anything I compared it with in a store. Then I posted about this on another platform, and someone pointed this distortion figure to me and although it was too late reluctantly I went back to the store and this time when streaming from my phone to a dac their i used the eq to push the highs and I realized what I overlooked, it outperformed the speaker I bought and even with the eq there is no grain or any audible flaw of any kind.

If anyone is running a room eq, it’s very important still to have a very low distortion as sometimes the eq applied would push certain frequencies to very higher levels and distortion rises with rise in loudness in most cases, on higher frequencies for many speakers this window is very low.

I learned this the hard way after making a very expensive (to me) mistake. The only reason I made the other post which started a conversation , (sorry @Vineethkumar01 for making a harsh comment there) was I don’t want another person to make the same mistake. I cannot the speaker name here (as It might defame the brand and hurt /trigger guys who own it)but it’s something stereophile reviewed this year and mentioned a bargain at around 7k dollars apparently he didn’t had the distortion graph, and to the horror I found it from a paid test which I bought later after my stupid decision of buying