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Topic: ABX, Where it fails and why. Another viewpoint (Read 5134 times) previous topic - next topic
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ABX, Where it fails and why. Another viewpoint

I can clearly hear 22000Hz, here's the ABX result.(the '22k.wav' is generated by Audition with fade in/fade out. If u use foobar's 'tone://22000,***' u'll hear a small noise at the beginning)

(it's not weird,most of my schoolmates can do that,all around 20 years old)



u may say what i heard is a distorted sound. well my tweeter is ScanSpeak 8513 and i used a large diaphragm consendor microphone to analyse the output spectrum of my speaker

(it's very noisy here & i held the phone in hand which made the low frequency noise bigger)



Well now comes the question. Few people can ABX out Lame insane MP3 & WAV in comon music files(including me), but the Lame insane preset simply cut off high frequency @ 20kHz. so, if u cannot distinguish several music files of different formats using ABX, u still cannot say that these formats makes no difference to ur ear---say,give me Lame insane MP3 & WAV of pure 22k sine waves i can surely distinguish them,MAYBE also with
some music with rich high frequency infos.

the detail of the ABX result:(sorry that's a Chinese version)

foo_abx v1.2 report
foobar2000 v0.8.3
2006/11/09 17:23:29

文件 A: file://C:\Documents and Settings\Administrator\桌面\22k.wav
文件 B: silence://10

17:23:30 : 测试开始.
17:23:42 : 01/01  50.0%
17:23:51 : 02/02  25.0%
17:23:56 : 03/03  12.5%
17:24:01 : 04/04  6.3%
17:24:07 : 05/05  3.1%
17:24:11 : 06/06  1.6%
17:24:23 : 07/07  0.8%
17:24:27 : 08/08  0.4%
17:24:34 : 09/09  0.2%
17:24:38 : 10/10  0.1%
17:24:42 : 11/11  0.0%
17:24:47 : 12/12  0.0%
17:24:52 : 13/13  0.0%
17:24:57 : 14/14  0.0%
17:25:01 : 15/15  0.0%
17:25:05 : 16/16  0.0%
17:25:09 : 17/17  0.0%
17:25:17 : 18/18  0.0%
17:25:21 : 19/19  0.0%
17:25:24 : 20/20  0.0%
17:25:44 : 21/21  0.0%
17:25:49 : 22/22  0.0%
17:25:53 : 23/23  0.0%
17:26:00 : 24/24  0.0%
17:26:05 : 25/25  0.0%
17:26:42 : 测试结束.

----------
总共: 25/25 (0.0%)

ABX, Where it fails and why. Another viewpoint

Reply #1 –
hearing a high frequency tone in isolation is no problem for many people
but i am sure you can't distinguish it when it's part of real music.

ABX, Where it fails and why. Another viewpoint

Reply #2 –
Quote from: Wenheng on
WAV of pure 22k sine waves i can surely distinguish them,



I'm very interested in the sample rate you are using, since 44.1 kHz will give you an average of 2 samples per sine wave. What you are hearing are aliasing frequencies.

ABX, Where it fails and why. Another viewpoint

Reply #3 –
Quote from: Hanky on
I'm very interested in the sample rate you are using, since 44.1 kHz will give you an average of 2 samples per sine wave.

So what? A sine wave is a sine wave. 

Quote
What you are hearing are aliasing frequencies.

There should be no (not much) aliasing if the sine wave is generated correctly, which is easy, btw.

ABX, Where it fails and why. Another viewpoint

Reply #5 –
 i'm using 48k samplerate and 24bit playback ,not AC97

ABX, Where it fails and why. Another viewpoint

Reply #6 –
OK, I generated a 22 kHz sine wave @ 48 kHz sample rate in Audacity and zoomed in, a screenshot is here. After looking at that waveform, redefine your understanding of 'pure sine wave'.

ABX, Where it fails and why. Another viewpoint

Reply #7 –
And again a wrong topic title. If abx results are not to be trusted, your test is invalid too, so you haven't proven you can hear 22kHz after all.
"We cannot win against obsession. They care, we don't. They win."

ABX, Where it fails and why. Another viewpoint

Reply #8 –
Quote from: Hanky on
OK, I generated a 22 kHz sine wave @ 48 kHz sample rate in Audacity and zoomed in, a screenshot is here. After looking at that waveform, redefine your understanding of 'pure sine wave'.
Please review sampling theory before you make claims like this. A 22kHz sine wave can be represented exactly by sampling at 44kHz or above - it just might not look like it in the wave view.

Wenheng - there are components around 100Hz that are only about 50dB down. It's possible that you are hearing those. That said, I can do up to 18kHz with a pure tone, so 20kHz isn't unbelieveable. With music samples, I can do 16kHz with "chenoa" and 15kHz with pretty much anything with cymbals.

ABX, Where it fails and why. Another viewpoint

Reply #9 –
Quote from: Hanky on
What you are hearing are aliasing frequencies.


Quote from: kjoonlee on
Remember AC97 and 48kHz resampling. Aliasing can occur at the resampling stage.


The measurment graphs show that there is absolutely no aliasing at all. The speaker plays a pure 22 kHz tone.

Quote from: cabbagerat on
Wenheng - there are components around 100Hz that are only about 50dB down. It's possible that you are hearing those.


I expect them to be present without the test signal too. It is unlikely that a 22 kHz stimulation can produce a 100 Hz artifact.

Quote from: Wenheng on
(it's not weird,most of my schoolmates can do that,all around 20 years old)


At this age, this ability is quite rare, though females usually have a better hearing than males.
Did your schoolmates listen to your speaker, or did they perform the experiment on their own ? In the later case, more than half of them should just hear the AC97 or multimedia soundcards aliasing, whose frequency is much lower.

ABX, Where it fails and why. Another viewpoint

Reply #10 –
Quote from: Pio2001 on
Quote from: kjoonlee on
Remember AC97 and 48kHz resampling. Aliasing can occur at the resampling stage.

The measurment graphs show that there is absolutely no aliasing at all. The speaker plays a pure 22 kHz tone.

Oops, I thought that was the spectrum before playback. My mistake.

ABX, Where it fails and why. Another viewpoint

Reply #11 –
Quote from: Hanky on
OK, I generated a 22 kHz sine wave @ 48 kHz sample rate in Audacity and zoomed in, a screenshot is here. After looking at that waveform, redefine your understanding of 'pure sine wave'.


Cool Edit Pro gives a good idea of how a digital wave is smoothed by the analog output of a CD player.
Here is a wav file, whose samples values are showed as rectangles :



here is a part of the same wav file, but the wave is recostructed between the samples, that are showed as green little squares instead of rectangles :



It's just a sine, like the 10 kHz one posted above. From those steppy rectangle, any CD Player is capable, as well as Cool Edit, to reconstruct the original sinewave. A capacitor ensures that the output is completely continuous, with no steps.

ABX, Where it fails and why. Another viewpoint

Reply #12 –
Quote from: Pio2001 on
At this age, this ability is quite rare, though females usually have a better hearing than males.
Did your schoolmates listen to your speaker, or did they perform the experiment on their own ? In the later case, more than half of them should just hear the AC97 or multimedia soundcards aliasing, whose frequency is much lower.

they listened to my speaker. 4 of the 5 could hear up to 20k+, the one left was a skilled violin player and he could only hear 15k
 

ABX, Where it fails and why. Another viewpoint

Reply #13 –
Quote from: Wenheng on
they listened to my speaker. 4 of the 5 could hear up to 20k+, the one left was a skilled violin player and he could only hear 15k

Interesting post. Good idea to capture the output of the speaker. You wrote that a large diaphragm microphone was used. These usually don't have a wide frequency range (tend to roll off at about 18 kHz). Do you have any idea about the SPL (sound pressure level) of the tone reproduced ? The human ear is less sensitive at high frequencies, so I can imagine that the playback level was rather high.
The ability to hear +20kHz tones doesn't necessarily mean that you can hear the effect of a 20kHz lowpass filter applied to music. The critical band is rather wide up there (a few kHz) so masking is likely. On the other hand, it seems you might be a good candidate for that kind of testing