Does 'envelopment' exist? Can it be measured?

[krabapple]

Well, we knew that relationship existed.. That is literally what 'envelopment' meant already: the feeling, from listening, of being in a larger space.
What's new in his report is a 'percept' involved in it that is due specifically to low-frequency (<200Hz) content..which he thinks is not 'heard' via the auditory system.

 

[Sokel]

Well, we knew that relationship existed.. That is literally what 'envelopment' meant already: the feeling, from listening, of being in a larger space.
What's new in his reports is a 'percept' involved in it that is due specifically to low-frequency (<200Hz) content..which he thinks is not 'heard' via the auditory system.

The main rant is about the old "there's nothing below 80Hz, treat it as you like, mono it, etc" which was mostly based on localization with sines and the misunderstanding of all music is summed to mono at bass.

We have lots of examples at the thread that bass at some recordings (vinyl also, as old as from the 50's) is either stereo or uncorrelated (which is all what this thing is about) .
That's the case he builds.

 

[krabapple]

That's not at all the 'main rant' on this thread.

Traditional LEV is due to delayed reflected sound. It seems from Lund's work that whatever he's testing is from direct subwoofer sound, as indicated in his outdoor test results.

The effect in low-pass filtered tests was also mainly limited to above 41 Hz, and was undetected below 30 Hz. So, to correct my previous interpetation, he's saying AE is an auditory effect of LF content, whereas 'VLF' content may pass through other sensoria.
TL is really big on 'dynamic' low frequency 'fluctuations' being preserved in recordings. He cites unpublished anecdota including the Genelec founders hiking experience, and this:

During reverb development two decades ago, even small, low frequency (<60 Hz) inter-aural variation at the listener made sound more enjoyable and spacious than if stimuli were interaurally static at low frequency. Test subjects actually started craving a dynamic LF, inter-aural experience, though it was never publicly reported. Still, fine reverbs are designed to promote that exact feeling in listeners, particularly when sound is reproduced in a small(er) room at home, which otherwise tends to destroy that aspect of a recording room or a concert hall [4]. .

[4] is D. Griesinger, General Overview of Spatial Impression, Envelopment, Localization, and Externalization. Proceedings of 15th annual AES conference, 1998.

 

[Sokel]

The LF fluctuations, be it amplitude or phase are dead easy to see if present at the recordings, just Deltawave the channels for example and it's obvious when they are there
(there's a true mono file Deltawave'd at the thread with the channels in perfect agreement, a good sanity test)

If our goal is the old "true to the recording" that's another aspect to look at.

Envelopment is not only about optimal set-up, whatever that is, it's about the recordings as well.

There's no way to create that 3D space, either low or high if the recording is not designed this way.
Heck, some recordings do not even have depth, at all, is like those rants at studios where the rock divas were fighting to the point they are all dead-centered and at equal loudness.

 

[Thomas Lund]

I hear trusted people use envelopment a lot. Can someone tell me what it is? How would I create more of it, assuming it's a good thing... There could be more than one use of the word.

Yes, “envelopment” is used in more ways than one. In short, what we have discussed is also its perceptual core, and not just the meta-parameter used in concert hall design, Listener Envelopment (LEV).

Envelopment is the sensation of being in a large space, arising from hearing delayed reflections of direct sounds.

The above is a description of LEV, which is not very relevant in reproduction. LEV also does not focus on envelopment's main perceptual cue, LF inter-aural fluctuation. Audio professionals designing reverb or mic arrays know about it, from “living stereo” to today’s 3D.

Auditory Envelopment puts a dedicated word to that. The abbreviation AEV was recently proposed rather than AE, so I will stick with the former below, but the two are the same.

Human sensitivity to inter-aural LF fluctuation has been studied for 40+ years [Jens Blauert, David Griesinger, Gilbert Soulodre, JJ, Tapio Lokki etc.]. My contribution has amounted to two minor elements, the separation of AEV from LEV; and the study of how any human from young children to very old people recognise and appreciate the sensation. The affective touch hypothesis is nothing more than that.

Reproduction ignorance probably stems from old studies claiming humans are unable to hear direction below 80 Hz, which recently was proven wrong again [Madalina Nastasa, Ville Pulkki]. Still, that devastating mistake has been endlessly repeated, leading to the flawed one-sub recreational sound principle, extended to ever higher x-over frequencies. Ironically, LF direction is an unimportant topic to most listeners, so the story could have ended there. However, everybody cares about AEV, and the emotions it can stir. AEV also reduces with the one-sub malpractice, and with other LF time-domain trivialization. That is the real shame.

I see why Floyd Toole does not focus on AEV - only so much can be achieved in recreational listening, and he has contributed so immensely to our understanding of directivity - but pragmatic is not good enough in monitoring. To gauge a recording, you must be able to transparently evaluate the space it brings, and the space it modulates. Monitoring is not about distorting a recording with constant listening room dominance, however pleasant it might seem.

AEV adds a whole emotion-inducing dimension to sound, so more should not be the goal.

 

[krabapple]

I see why Floyd Toole does not focus on AEV - only so much can be achieved in recreational listening, and he has contributed so immensely to our understanding of directivity - but pragmatic is not good enough in monitoring. To gauge a recording, you must be able to transparently evaluate the space it brings, and the space it modulates. Monitoring is not about distorting a recording with constant listening room dominance, however pleasant it might seem.

"Envelopment is the sensation of being in a large space, arising from hearing delayed reflections of direct sounds."
I got that from Toole & Olive , 2025. I assume it is the standard use of the word.

Their book is about "The Acoustics and Psychoacoustics of Loudspeakers and Rooms" -- mainly, as heard in consumer's rooms but drawing on research into large room acoustics as well.

Is that listening, in consumers' rooms, what you mean by 'monitoring'? Or are you referring to the production side (which is out of the control of consumers)?

'Envelopment' as T&O use it can also be achieved with multichannel reproduction, which takes 'room dominance' greatly out of the envelopment picture.

 

[Oddball]

Reproduction ignorance probably stems from old studies claiming humans are unable to hear direction below 80 Hz, which recently was proven wrong again [Madalina Nastasa, Ville Pulkki]. Still, that devastating mistake has been endlessly repeated, leading to the flawed one-sub recreational sound principle, extended to ever higher x-over frequencies. Ironically, LF direction is an unimportant topic to most listeners, so the story could have ended there. However, everybody cares about AEV, and the emotions it can stir. AEV also reduces with the one-sub malpractice, and with other LF time-domain trivialization. That is the real shame.

Apologies if I am digressing the thread. But would just like to better understand what @Thomas Lund thinks about directivity of the sub 80hz frequencies. To put things in perspective, I also strongly believed that at this frequency something else - like directivity - might be start to happen.

But as of recent, it seems that I am getting great directivity with ART that does it's own thing and often still uses 80hz support from the subs despite quite large speakers. My experience is mostly for soundtracks as kind of got out of the music at this point. Hopefully interest for music will come back, as it always did.

 

[krabapple]

Can you measure the output of the subs with ART active? Specifically the >=80 Hz output? (Since the low pass filters in common use are not brickwall.)

 

[dagfinn]

Apologies if I am digressing the thread. But would just like to better understand what @Thomas Lund thinks about directivity of the sub 80hz frequencies. To put things in perspective, I also strongly believed that at this frequency something else - like directivity - might be start to happen.

But as of recent, it seems that I am getting great directivity with ART that does it's own thing and often still uses 80hz support from the subs despite quite large speakers. My experience is mostly for soundtracks as kind of got out of the music at this point. Hopefully interest for music will come back, as it always did.

Here's the paper he mentioned.

Auditory localisation of low-frequency sound sources

research.aalto.fi

Auditory localisation of low-frequency sound sources​

• Madalina Nastasa *
• , Ville Pulkki
• , Aki Mäkivirta

"Abstract
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."

https://acris.aalto.fi/ws/portalfiles/portal/162353409/ACRIS_Auditory_Localisation_of_LF_Sources.pdf

 

[Oddball]

Here's the paper he mentioned.

Auditory localisation of low-frequency sound sources

research.aalto.fi

Auditory localisation of low-frequency sound sources​

• Madalina Nastasa *
• , Ville Pulkki
• , Aki Mäkivirta

"Abstract
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."

https://acris.aalto.fi/ws/portalfiles/portal/162353409/ACRIS_Auditory_Localisation_of_LF_Sources.pdf

Many thanks and will have to digest. The fact that it was conducted in anechoic room does not fill me with confidence though.

 

[dagfinn]

Many thanks and will have to digest. The fact that it was conducted in anechoic room does not fill me with confidence though.

Not sure why you distrust the use of a precious resource like an a.e.c., it's a well established research tool used to simulate free field (which is hard to work in). Anyway, this is paper is related and both relevant and interesting too. But more aec .

"Impact of standing waves on human auditory perception of low-frequency direction

Author (s): Nastasa, Madalina; Pulkki, Ville; Mäkivirta, Aki
Affiliation: Department of Information and Communications Engineering, Aalto University, Espoo, Finland; Department of Information and Communications Engineering, Aalto University, Espoo, Finland; Genelec Oy, Iisalmi, Finland (See document for exact affiliation information.)

Abstract
This paper studies the effect of room modal resonances on the localisation of very low-frequency sound sources. A subjective listening test is conducted with 20 participants in an anechoic chamber, where the listener must detect the direction of the sound source for pure sinusoids at 31.5, 50 and 80 Hz. A synthetic standing wave pattern modelling a room resonant effect is created with two additional sound sources located at the left and the right side of the listener. Results show that the perception of low-frequency direction is negatively impacted by the minimum pressure node of the standing wave, even when the standing wave has a relatively low level, whereas the maximum pressure node does not have as strong of an effect. The results of the experiment demonstrate that in the low-frequency spectrum, direction judgement is strongly impacted by room resonances. The localisation ability in this frequency range depends on the direction of the direct sound in comparison with the position of the standing wave, and the level difference between the direct sound and the standing wave."

https://acris.aalto.fi/ws/portalfiles/portal/139838618/Impact_Standing_Waves.pdf

 

[Oddball]

Not sure why you distrust the use of a precious resource like an a.e.c., it's a well established research tool used to simulate free field (which is hard to work in). Anyway, this is paper is related and both relevant and interesting too. But more aec .

"Impact of standing waves on human auditory perception of low-frequency direction

Author (s): Nastasa, Madalina; Pulkki, Ville; Mäkivirta, Aki
Affiliation: Department of Information and Communications Engineering, Aalto University, Espoo, Finland; Department of Information and Communications Engineering, Aalto University, Espoo, Finland; Genelec Oy, Iisalmi, Finland (See document for exact affiliation information.)

Abstract
This paper studies the effect of room modal resonances on the localisation of very low-frequency sound sources. A subjective listening test is conducted with 20 participants in an anechoic chamber, where the listener must detect the direction of the sound source for pure sinusoids at 31.5, 50 and 80 Hz. A synthetic standing wave pattern modelling a room resonant effect is created with two additional sound sources located at the left and the right side of the listener. Results show that the perception of low-frequency direction is negatively impacted by the minimum pressure node of the standing wave, even when the standing wave has a relatively low level, whereas the maximum pressure node does not have as strong of an effect. The results of the experiment demonstrate that in the low-frequency spectrum, direction judgement is strongly impacted by room resonances. The localisation ability in this frequency range depends on the direction of the direct sound in comparison with the position of the standing wave, and the level difference between the direct sound and the standing wave."

https://acris.aalto.fi/ws/portalfiles/portal/139838618/Impact_Standing_Waves.pdf

Perhaps because I have been studying that all my life and continue to be a student willing to learn from reasonable sources

 

[quattro98]

This video may be of interest.

 

[krabapple]

This video may be of interest.

This talk explains why we need not suffer the flat, lifeless bass sound that results from a single subwoofer, or a single subwoofer output on a receiver. Contrary to current practice we put two or more low-frequency drivers where they avoid exciting strong medial modes while emphasizing medial modes. If all else fails, a pair of stereo at the sides of the listeners can be very effective

Huh?

 

[Oddball]

Right, how about 4 subs down to 20hz, LCR down to 30hz, Back surrounds down to 40hz, Front wides and Side surrounds to 50hz, Atmos to 50hz? Then you run Dirac ART and your jaw just drops. Like OMG, what just happened - how did I deserve to get to this place where things are so different than they were?

Given how recent ART is probably not much of thick papers about it. But it changes the game up and down and all around.

EDIT: Still have REW and my ears to evaluate and understand what's been happening. Their algo is proprietary though so we don't know how exactly that happens.

 

[quattro98]

This talk explains why we need not suffer the flat, lifeless bass sound that results from a single subwoofer, or a single subwoofer output on a receiver. Contrary to current practice we put two or more low-frequency drivers where they avoid exciting strong medial modes while emphasizing medial modes. If all else fails, a pair of stereo at the sides of the listeners can be very effective

Huh?

Typo on YT.

Minimize medial modes while maximizing lateral modes.
David Greisinger has advocated for stereo bass and speakers to the side of the listener.

 

[john61ct]

The "only play what was intended" philosophy and "only reproduce what was recorded" are similar

Envelopment is not only about optimal set-up, whatever that is, it's about the recordings as well.

There's no way to create that 3D space, either low or high if the recording is not designed this way.

That only is true when trying to adhere to those philosophies, right?

Simulated DSP / surround effects for concert halls, jazz clubs, stadium etc try to do exactly that.

Even Schiit SYN can have a great impact on with its Width and Presence adjustments, not just in a surround speaker context but also headphones.

Very much does depend on the music and its recording technology used

but neither the musicians nor the engineer(s) intent had anything to do with the relative success of these tools' attempt at adding to the perception of envelopment.

Note I am not talking here about films' soundtracks nor any "encoding standards", just vanilla stereo content whatever the media used.

 

[Sokel]

The "only play what was intended" philosophy and "only reproduce what was recorded" are similar

That only is true when trying to adhere to those philosophies, right?

Simulated DSP / surround effects for concert halls, jazz clubs, stadium etc try to do exactly that.

Even Schiit SYN can have a great impact on with its Width and Presence adjustments, not just in a surround speaker context but also headphones.

Very much does depend on the music and its recording technology used

but neither the musicians nor the engineer(s) intent had anything to do with the relative success of these tools' attempt at adding to the perception of envelopment.

Note I am not talking here about films' soundtracks nor any "encoding standards", just vanilla stereo content whatever the media used.

Where the sell goes is at the control room with the mains monitors.
Is it fair to assume that musicians and engineers intent is about that sound?

There's all kinds out there, I agree.
But the recording, apart from the sanity aspects (where they are at place) is a design right from the mic and mic trees placement (I only talk about stereo as well, and classical to be fair, that's what I listen to)

Some are like a dense wall from speaker to speaker, some are beautiful creating a 3D field.
The curse of the classical repertoire is that we have the same works at 47948573475 versions, variations, halls to compare, and most importantly the live performance reference.

The later always reminds us the impossibility to chase it, so we stick to the recordings and how to faithfully playback them.
Far easier and the brain does the rest.

Edit: Lund talked about the "Living Stereo" era at 50's. These heroes managed to create depth at their recordings just out of pure skill. It's a shame that some of the today's alleged "magicians" can't do the same.

 

[john61ct]

old studies claiming humans are unable to hear direction below 80 Hz... flawed one-sub recreational sound principle, extended to ever higher x-over frequencies

Forgive the intrusion, but would really appreciate your input. I am working on creating a multi-channel multi-subs system, with Schiit SYN in the chain.

The core is a pair of LS50 as main front / high, with one pair of "basstand MBM" bandpassed to extend / reinforce the LF content in stereo. Setting aside their top crossover for now, I'm thinking / hoping they will also deliver decent SPL down below 80-90Hz

I am also skeptical of that content being fully non-directional at an arbitrary hard-edged bright-line frequency

Therefore, I am considering also using a third **stereo pair** designed for "true subwoofer" bandwidth content*

I may also add one or more **mono-fed** sub boxen with placement flexibility to help with room modes.

So finally, my questions, for anyone, including any feedback welcome on the above

1. Where in the spectrum do YOU think the crossover should be between the stereo sub pair, and the mono "true sub" lower down?

In order for me to test listen and measure to make my own decision on the above in my listening spaces (including outdoors)

2. Can you recommend vanilla 2-channel source content (prefer music, but maybe also films) with plenty of LF recorded **in stereo** well below where most engineers sum to mono?

Synthesized test signals too I suppose.

*down to ~20Hz or even lower if possible, for films and also subsonic content in music, say from pipe organ, big drums and cello / double bass.

 

[krabapple]

Typo on YT.

Minimize medial modes while maximizing lateral modes.
David Greisinger has advocated for stereo bass and speakers to the side of the listener.

His ppt deck is full of typos too.