Bass direction is audible

[Keith_W]

I was sent this article: Auditory Localisation of Low Frequency Sound Sources (Nastassa, Pulki, Makivirta, AES Convention 154 2023). Unfortunately I only have access to the abstract. I have quoted it in full:

It is generally thought that humans cannot detect the direction of sound in the very low-frequency spectrum, although some studies suggest that the sense of direction also exists at the lowest audible frequencies. In the current work, a 2AFC localisation experiment is conducted with 18 participants, where the listener must detect a change in the direction of pure tones and octave band filtered pink noise bursts in the frequency range of 31.5 to 100 Hz. The angular separations between the low-frequency sound events utilised in the test are 10, 20, 25, 35 and 45 degrees in the left azimuth plane. The results agree with those studies showing that humans can localise even the lowest audible frequencies. Changes in direction as small as 10 degrees can be reliably detected for pink noise bursts from 31.5 Hz and for pure tones from 63.5 Hz. The psychoacoustic experiment was conducted in an anechoic room with minor room resonances which caused a significant change in the directional judgement for the affected frequencies, demonstrating how strongly room resonances can interact with directional hearing in the low-frequency spectrum.

Note that the study was done in an anechoic chamber. The lowest frequency of 31.5Hz is about 10m long, surely this can not be audible in an average listening room?

If this study is correct, it would have implications as to how we should position subwoofers in our listening rooms. Maybe Griesinger's "stereo sub" idea may have some merit. Subwoofer positioning schemes such as Geddes' 3 sub method, or two subs in diagonal corners would need rethinking. Opinions?

EDIT: paper is available for download. See @NTK post here.

 

[staticV3]

If this study is correct, it would have implications as to how we should position subwoofers in our listening rooms.

Why though? Or listening rooms are not anechoic chambers.

The author explicitly pointed out that the lack of room reflections in the test caused a significant change in the directional judgement.

So why would the results w/o room reflections be relevant to our listening environments w/ room reflections?

 

[Keith_W]

Why though? Or listening rooms are not anechoic chambers.

I agree, and I pointed it out in my post. I am not aware of any studies that shows that bass direction is audible (or not) in a listening room, and what the lower limit might be. Do you know of any?

 

[dlaloum]

I was sent this article: Auditory Localisation of Low Frequency Sound Sources (Nastassa, Pulki, Makivirta, AES Convention 154 2023). Unfortunately I only have access to the abstract. I have quoted it in full:



Note that the study was done in an anechoic chamber. The lowest frequency of 31.5Hz is about 10m long, surely this can not be audible in an average listening room?

If this study is correct, it would have implications as to how we should position subwoofers in our listening rooms. Maybe Griesinger's "stereo sub" idea may have some merit. Subwoofer positioning schemes such as Geddes' 3 sub method, or two subs in diagonal corners would need rethinking. Opinions?

Full range speakers for the Base 5 or 7 channels - most full rangers will go down to 35Hz or less.... so they cover the directional spectrum

 

[JSmith]

This is an small extract of that cited paper, the conclusion;

In this study, the extent of the human ability to perceive changes in the direction of low-frequency sound sources was studied through a psychoacoustic experiment in an anechoic chamber. The results of the 2AFC localisation experiment, conducted with 18 participants, agree with the studies showing that humans can localise even the lowest audible frequencies, and indicate that the spatial resolution of the auditory system in the low-frequency spectrum goes beyond a left-right discrimination. Changes in direction as small as 10 degrees can be reliably detected for pink noise bursts from 31.5 Hz and for sinusoids from 63.5 Hz. In addition, the localisation ability has been greatly impeded at frequencies which present strong modal resonances, demonstrating that the directional hearing of low-frequency sound sources highly depends on the acoustical properties of the listening environment.
Nevertheless, the results of this research suggest that the ability to localise low-frequency sound sources is an innate quality of the human auditory system.

This paper may be of interest as well though from 2013 which is freely accessible;

https://www.researchgate.net/publication/258926939_Low-frequency_sound_source_localization_as_a_function_of_closed_acoustic_spaces

Overall, the theory of low-frequency localization in closed spaces is now better understood. Where previous work makes gross generalizations (such as nothing under 100 or 200 Hz can be localized in any space), this research has shown that the minimum localizable frequency is a function of the configuration of a space (dimensions, source/listener location, absorption).

JSmith

 

[DanielT]

I was sent this article: Auditory Localisation of Low Frequency Sound Sources (Nastassa, Pulki, Makivirta, AES Convention 154 2023). Unfortunately I only have access to the abstract. I have quoted it in full:



Note that the study was done in an anechoic chamber. The lowest frequency of 31.5Hz is about 10m long, surely this can not be audible in an average listening room?

If this study is correct, it would have implications as to how we should position subwoofers in our listening rooms. Maybe Griesinger's "stereo sub" idea may have some merit. Subwoofer positioning schemes such as Geddes' 3 sub method, or two subs in diagonal corners would need rethinking. Opinions?

It would be interesting to know what type of subwoofer/bass module was used and above all what kind of LP filter they had.

Were there audible artifacts, sounds in higher frequencies, above the mentioned 31.5 Hz and 63.5 Hz? It is quite decisive for the result.

Edit:
Sorry I missed, or forgot that it was pure tones that was used in the test. Then there probably won't be any problem with higher frequency artifacts if the test is performed correctly (which one can assume it was). On the other hand, listening to music in your living room/ listening room, then factors that sigbergaudio mentions in #9 will play a role.

 

[sigbergaudio]

There's a long thread about this here somewhere, couldn't find it right now. I think the general answer (disregarding very special situations and/or golden eared individuals) is that no, this is not a real world problem.

 

[Sokel]

@Thomas Lund calls this ability "super power" and he states that we don't loose it when being in a room.
I never-ever experienced right proportions with subs far and crossed high (more than 60Hz) and I suspect localization is one of the causes.

 

[sigbergaudio]

I think one must discern between what is possible in controlled experiments, and what has practical implications for how we set up our systems.

The more asymmetric the setup, and the higher it is crossed over, the more likely it is you may have localization issues. But this is a gliding scale, depends on typical music material, crossover slopes, the room, the sensitivity of the listener, etc. It's not a black and white thing.

 

[Sokel]

I agree, and I pointed it out in my post. I am not aware of any studies that shows that bass direction is audible (or not) in a listening room, and what the lower limit might be. Do you know of any?

Here's lots of them with summary,really good thread:

Bass and subwoofers

This is the second in a series of follow-up posts to https://www.audiosciencereview.com/...-of-lokki-bech-toole-et-al.27540/#post-950580, this time focussing on bass perception with a brief digression on subwoofers, since there's relevance to (reproduction of) concert hall acoustics. I’ve...

www.audiosciencereview.com

 

[Keith_W]

Thanks for the link @Sokel!

Can someone tell me what "2AFC" is please?

 

[JSmith]

Can someone tell me what "2AFC" is please?

Two-alternative forced choice.


JSmith

 

[Ramon Cota]

I recently made a small experiment. I fed summed mono signal to one of my speakers woofers( i have active speakers with 8ch dac), the other one was completely off . Crossofer to mids was 800 hz lr4 , speakers 1 meter apart listening position two meters from speakers. If i didnt know which woofer was playing i couldnt reliably tell.It sounded as if both were playing. I need to redo this with speakers set further apart.

 

[Bjorn]

A lot things are not audible if the room has poor acoustics and/or we have other masking effects. It's one of the reasons why need to be careful about raising the scientific flag.

I experienced this myself when I used a subwoofer in the rear and with an xover at 80 Hz. I had to lower to 50 Hz. The room was not anechoic by any means but did have some low frequency treatment.

Eventually I completely moved away from having an additional subwoofer in the rear and had better bass quality with subs only in the front.

 

[holdingpants01]

I did some test in my room with different subwoofer placements and I can tell you that even if you cannot pinpoint the bass source below certain frequency, it doesn't mean it sound the same regardless of the placement. I don't mean the differences in frequency response, I calibrated subs every time I moved them resulting in similar curve, but sub on the side wall didn't sound the same as sub between the speakers, it was rather annoying to be honest. If you have drywall room, or heavily bass trapped with quick bass decay it's even more apparent. Then there's the material type which is used in tests, constant sinusoidal waves sometimes cannot be pinpointed at any frequency, let alone on the low end spectrum, but impulses or sounds out of phase are a different story.

Another thing is how the anechoic room was really anechoic in the low end?

Anyway, here's a post with a lot of sources that could be interesting to you: https://www.audiosciencereview.com/forum/index.php?threads/bass-and-subwoofers.51589/

 

[Justdafactsmaam]

Why though? Or listening rooms are not anechoic chambers.

The author explicitly pointed out that the lack of room reflections in the test caused a significant change in the directional judgement.

So why would the results w/o room reflections be relevant to our listening environments w/ room reflections?

So is this an argument against concerns over spatial perception in the deep bass or an argument in favor of maximum use of bass trapping so we can enjoy true stereo all the down to a he deep bass?

 

[staticV3]

So is this an argument against concerns over spatial perception in the deep bass or an argument in favor of maximum use of bass trapping so we can enjoy true stereo all the down to a he deep bass?

Neither. It's a reminder to avoid jumping to conclusions.

Read the paper carefully, pay attention to the test conditions, then consider how the results may or may not be applicable to other situations.

Since the paper found bass to be localizeable down to very low frequencies, in an anechoic environment, I would for example be mindful of that when setting up PA for an open-air concert.

For typical home audio applications, the results seem hardly relevant.

 

[Hear Here]

I can imagine that many humans can detect approximate source locations of that frequency range if those are the only frequencies being generated.

However if the full range is present (as happens with music), and the source location of only those low frequencies was moved. we would be highly unlikely to notice. As most subs are (probably) set for a lower XO than 100 Hz, the likelihood of detections of different sub positions would become even less.

 

[krabapple]

Another case of audio science showing that something can be perceived, not that it typically is perceived.

Such results tend to excite those looking for validation that they perceive the something. Even though the experimental conditions indicate that that's unlikely.

 

[Justdafactsmaam]

Neither. It's a reminder to avoid jumping to conclusions.

Read the paper carefully, pay attention to the test conditions, then consider how the results may or may not be applicable to other situations.

Since the paper found bass to be localizeable down to very low frequencies, in an anechoic environment, I would for example be mindful of that when setting up PA for an open-air concert.

For typical home audio applications, the results seem hardly relevant.

How is that conclusion, that it hardly seems relevant to home audio applications not jumping to a conclusion?