Can the human ear really localize bass? - diyAudio
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Old 16th December 2013, 01:35 AM   #1
Bill F. is offline Bill F.  United States
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Default Can the human ear really localize bass?

Everyone seems to design as if stereo bass is important, but I am skeptical.

Can anyone point me to a scientific study of human sound localization vs. frequency? I am less interested in personal anecdotes of "I can be spun around blindfolded 100 times and shoot a 50Hz tone right between the eyes every time."

I did some concerted Google-fu but came up wanting. The following excerpt from the Wikipedia article on sound localization was somewhat helpful:

Quote:
Evaluation for low frequencies

For frequencies below 800 Hz, the dimensions of the head (ear distance 21.5 cm, corresponding to an interaural time delay of 625 s), are smaller than the half wavelength of the sound waves. So the auditory system can determine phase delays between both ears without confusion. . . . As the frequency drops below 80 Hz it becomes difficult or impossible to use either time difference or level difference to determine a sound's lateral source, because the phase difference between the ears becomes too small for a directional evaluation.[citation needed]
That little "citation needed" part is the irksome bit. I imagine 80Hz isn't a brick wall. So how much above 80Hz does the perceptual system begin to lose its grip? If we can localize laterally to within 1 degree at 1kHz, How many degrees of uncertainty have we accumulated down at 150Hz?

And none of this addresses the question of vertical localization of low frequencies where interaural time delay cannot be the mechanism. I seem to remember reading something about the brain estimating low-frequency source elevation by analyzing floor-bounce cancellations...
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Old 16th December 2013, 03:11 AM   #2
jcx is offline jcx  United States
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sub frequencies are modal in small rooms - dominated by standing wave resonances and location of speakers relative to boundaries

there's no "floor bounce" at 50 Hz with most speakers sitting closer than 1/4 wave, 5' to the floor
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Old 16th December 2013, 03:21 AM   #3
Pano is offline Pano  United States
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Bill, on the flip side prove to us that it is not. I can do it blindfolded. But if using pure tones it can be hard to locate most sounds. Use band filtered noise and it's much easier. Try it yourself.

I know you said no personal stories, but I want to see solid evidence that it is not before I believe that it is not.
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Old 16th December 2013, 05:57 AM   #4
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Everyone seems to design as if stereo bass is important, but I am skeptical.
It is important if you only want to design and build two boxes.

Silliness aside, it may come down to different personal levels of perception. Some, like Pano, can differentiate while others may have a different threshold level. It may well come back to the lower level of difficulty and lower use of floor space to incorporate all of the bass drivers into the stereo boxes.

My question is; why are you asking the question? (As you well know, such open questions often invite comments from people with "odd" ideas, many of whom are on my ignore list.) Do you wish to open a large can-of-worms that will, in all probability, offer nothing more than an exercise in the abstruse.
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Old 16th December 2013, 06:23 AM   #5
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Someone needs to make a test.
Put sub boxes all over a room. As many as can be built and afforded. Even empty boxes for placebo. Just make them down firing, or place woofer away from listener. Blindfolds even.
You can use a minidsp or something with multiple line outs with volume controls for each sub. Adjust volume of each sub one at a time randomly and have listener point to where they think the sound is coming from.

With minidsp the crossover can be fiddled with. So the crossover point can be raised and lowered to see what effect it has as crossover is changed.
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Old 16th December 2013, 08:21 AM   #6
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Yes it can, in free-field or in a large room.

Not so clear in a small room, where modal effects dominate. We can hear 'something' resembling a localization cue, but you could argue it is a false que, due to sitting near a pressure gradient.
Griesinger used to argue for it while he was at Harman, but it was found that a) >99% recordings don't support it and b) if everything is optimized for this effect, it is still marginal at best. Harman went for SFM instead. Contrary to the 'spatial bass' effect, taking care of modal problems is clearly audible on every recording (containing frequencies <200Hz) and the effect is not marginal.

If you have a Lexicon processor, there is a 'bass enhance' function, or you could DIY the same thing: don't sit in the rooms centreline, bass sources 90deg left and right, phase of one source lags the other ~90deg.
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Old 16th December 2013, 08:43 AM   #7
gk7 is offline gk7
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Quote:
Originally Posted by TMHutson View Post
Someone needs to make a test.
Put sub boxes all over a room. ...
I think its important to keep in mind that these boxes will have resonances and harmonics (distortion) occurring at higher frequencies which will make it easy to localize them. For a real test one would need some source of a pure low frequency.
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Old 16th December 2013, 11:25 AM   #8
JLH is offline JLH  United States
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Ask Danley if you can borrow their Matterhorn subwoofer container. Park it in an empty corn field in the middle of Nebraska and spin a blindfolded listener on a swiveling bar stool.
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Old 16th December 2013, 12:14 PM   #9
sangram is offline sangram  India
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If it's a musical instrument playing a tone, yes, it can be localised.

Because most instruments generate lots of harmonics. However common music recording techniques concentrate on putting as much of the actual low frequency at the center because of phase issues, though sometimes engineers may choose to leave LF where it actually occurs. For example, the floor toms in Hotel California, or in James Taylor 'Gaia' can only be properly reproduced with full-range speakers on either side (I don't mean one speaker full range, but 20-20k ability with decent SPL)

If it's a subwoofer+main speakers or woofer playing back that tone with it's own distortions, again, yes. Even with the LF portion of the tone emanating only from the center we can pick out the pluck of strings or bow - and the brain tends to localise the sound source - assuming a good room and speakers. It would be impossible to record double bass drums without, and that's just one example.

A pure single 50Hz in an anechoic environment - maybe, but then is that a scientific question rather than relevant to real speakers in real rooms playing back music?

Last edited by sangram; 16th December 2013 at 12:17 PM.
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Old 16th December 2013, 12:31 PM   #10
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Quote:
Originally Posted by Pano View Post
Bill, on the flip side prove to us that it is not. I can do it blindfolded. But if using pure tones it can be hard to locate most sounds. Use band filtered noise and it's much easier. Try it yourself.

I know you said no personal stories, but I want to see solid evidence that it is not before I believe that it is not.
I'll second this, modes be damned
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