Re: [AUDITORY] speakers at ear level

["Richard F. Lyon" <0000030301ff4bce-dmarc-request@xxxxxxxxxxxxxxx>]

I think that when Samuel asked about speakers "below (even if angled up toward the ears)", he was at least partly acknowledging the speaker directional effects that Chris is describing.  If the speakers are "angled up" to be "aimed" at the ears, there should be much less falloff of high frequencies.  Yet the quality is rather different.

I suspect that one needs to get into HRTF, particularly the "torso reflection" part of the HRTF, to explain why a sound from a negative elevation has such a different quality.  In particular, the torso reflection induces a destructive interference that makes a comb filter effect even down in the 1-3 kHz region (path differences of a half wavelength being about 2 to 6 inches in that region).  

You can see some of what I'm talking about in my book, figure 22.7 ( https://dicklyon.com/hmh/Lyon_Hearing_book_01jan2018.pdf ).  

There's more about this torso reflection effect in these papers, which are easy to find:

Lan, Y., Yin, T., & Yu, G. (2022). Effect of torso reflections from simplified torso models on head-related transfer function simulation and ipsilateral perception of elevation. Applied Acoustics, 201, 109095.

Reijniers, J., Partoens, B., & Peremans, H. (2023, September). Torso reflection model for dynamic head-related transfer function. In Proceedings of the 10th Convention of the European Acoustics Association (EAA), Torino, Italy (pp. 11-15).

Dick

On Fri, Jun 20, 2025 at 1:43 AM Krzysztof Basiński <k.basinski@xxxxxxxxxxxx> wrote:

Sam,

I’m no physicist but was a sound engineer once… The phenomenon you're describing is well known and has to do with the directionality of high frequencies. What they tell you in sound engineering 101 is to place your tweeters at ear level because they are the ones that emit high frequencies (~ 1-2 kHz and higher). Woofers can be lower, higher, whatever you want because they emit low and mid frequencies.

Here’s a nice little blog post that tries to explain the physics of it: https://www.theaudioblog.org/post/why-high-frequencies-are-directional-and-low-aren-t . I don’t think there’s much psychology here to be honest - just the fact that your auditory system receives less high frequency power when your ears are not level with the tweeters.

I’m sure there are much more competent people here that will be able to explain the physics in greater detail… but hope this helps.

Best,

Chris

--

Krzysztof Basiński, PhD
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Auditory Neuroscience Laboratory

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Division of Quality of Life Research
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On 19 Jun 2025, at 12:07, Samuel Mehr <sam@xxxxxxxxxxxxxx> wrote:

Hi all, I was moving offices, set up speakers at my desk and was reminded of the quite striking difference in sound quality when speakers are at ear level vs below (even if angled up toward the ears). 

I was just wondering if anyone has resources explaining why this phenomenon occurs — has this been studied in any depth? I imagine the physics of it are plain enough to model, but one also wonders about the psychology of it, which probably is less straightforward.

thanks,
Sam

———
Samuel Mehr
School of Psychology, University of Auckland
and Child Study Center, Yale University
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