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Old 26th August 2013, 03:56 PM   #1
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Default Localisation of very low frequencies sounds

Hello

I know that under 80 hz it should become very difficult to localize a sound.

I did want to test my low frequencies earing and sound localisation. So I use my sinewave generator and for a first test I did a 500 hz to 25 hz sweep tone test on the right channel speaker only, and after I did the same sweep tone test on the left channel speaker only.

I both tests I could easily localize the sound, even down to 35 hz.

Under 80 hz it should become very difficult to localize the sound, but I could easily localize the very low frequencies sounds. Did I done an error in my test, or some peoples can more easily localize very low frequencies sounds ?

Thank

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Gaetan

Last edited by gaetan8888; 26th August 2013 at 04:04 PM.
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Old 26th August 2013, 04:01 PM   #2
tomtom is offline tomtom  Slovakia
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You have to be sure that your bass system is free of harmonic distortion \to reasonable scale\. Otherwise you can localize harmonic product of tone you are playing
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Old 26th August 2013, 04:07 PM   #3
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Hello

I use a KROHNHITE sine generator, my amp have .002 % thd at 10 hz, and I have Dynaudio loudspeakers, thd of my Dynaudio are .5 % at 10 hz and .1 % at 100 hz.

Thank

Bye

Gaetan

Last edited by gaetan8888; 26th August 2013 at 04:24 PM.
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Old 26th August 2013, 05:00 PM   #4
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^ Pressure gradients due to room modes can give misleading localization cues.

Other than that, do you have single sines, e.g. 35Hz? Close your eyes, turn around a couple of times until you don't know anymore which direction you're facing then play those 35Hz from one speaker with your eyes still closed. Are you still able to localize the speaker?

P.S. 0.5% THD at what SPL? My speakers have 0% THD when turned off

Last edited by markus76; 26th August 2013 at 05:02 PM.
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Old 26th August 2013, 05:14 PM   #5
ra7 is offline ra7  United States
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0.5% THD at 10 Hz? Highly unlikely. Also, which mic did you use to measure THD at 10 Hz?

Do what Markus suggests, single tone, rotate around. Then try to localize.
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Old 26th August 2013, 07:29 PM   #6
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I am all but positive you were hearing distortion, and probably also giving yourself an illusion by running sweeps. You brain is plenty smart enough to remember where the sound is coming from as it sweeps down. Approaching 10m wavelengths, there's always going to be some other explanation. Another interesting thing to do is play 35Hz on one side, and 140Hz on the other side.

Last edited by dumptruck; 26th August 2013 at 07:32 PM.
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Old 26th August 2013, 07:52 PM   #7
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This is a highly interesting issue. On the one hand it is true that if you walk into a room in which a 35 Hz tone is played you'll find i very difficult to determine where its source is. On the other hand some time ago I read an article which claims that the ear is very sensitive to the sound/no sound dichtomy. This menas that you'll most likely be able to determine the position of the sound source - i.e. where the sound started, because that is in effect an impulse. And then - just as dumptruck mentions - you ear-brain combination will remember that. And this is precisely the tricky point when we're talking about integration between side systems and subwoofers. The ear is sensitive to the sound/no sound binary. Thus it'll be sensitive to the location of the onset of a deep bass note. Only if the fundamental and the higher harmonics are in phase/timealigned will the ear accept it as coming from somewhere specific in the phantom image. A single subwoofer will never be correctly timealigned with the sidesystem, thus it'll be very diffcult to integrate the two systems. The only remedy is two subwoofers. This may also explain why single subwoofers have earned the nickname of "boom box". (Sorry I don't remember where I read about our superb ability to localize sound/no sound information!) But it may all be speculation.
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Old 26th August 2013, 08:05 PM   #8
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Old 26th August 2013, 08:07 PM   #9
badman is offline badman  United States
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I agree with dumptruck- you were probably influenced by factors you didn't realize. .5 % THD at 10Hz simply doesn't happen at any reasonable SPL. Not even close. 9-10% is world-class performance that low.
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Old 27th August 2013, 02:08 AM   #10
Pano is offline Pano  United States
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I've run similar tests with sines and bandwidth limited noise. You do have to be careful of distortion giving you clues. But some people are just better at LF localization than others. Of all the audio techs I've tested, I have a much better ability at LF than any of them. Up higher, I'm no better, maybe worse.

You also have to remember that when someone tells you you can't locate bass under 100Hz (or whatever) that may be true for pure tones or even noise with no harmonics. But your subwoofer that you cross at 100Hz will certainly have harmonics, and you'll hear its position. A case of pure vs practical applications.
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