Perceptual Effects of Room Reflections

[dasdoing]

research on preference

is nice,

but who ever considers this path has without a doubt another preference then the mainstream.
it will hardly ever be close to a anaechoic chamber.

 

[Wes]

I'll toss these excerpted tidbits into the mix:



Toole, F. E. 2006. Loudspeakers and Rooms for Sound Reproduction—A Scientific Review J. Audio Eng. Soc., Vol. 54, No. 6 June

Living rooms are in the transitional region, where the direct and early reflected sounds dominate, and late reflected sounds are subdued, and progressively attenuated with distance. The sound field is not diffuse, and there is no critical distance, as classically defined. SPL declines ~~ 3dB as distance doubles - p. 455

The late reflected sound field is greatly diminished with distance from the source. These are not “Sabine” spaces, and it is not appropriate to employ calculations and measurements that rely on assumptions of diffusivity. - p. 456

• Localization (direction)—the precedence effect; cognitive effect of direct sound setting location in the brain

• Localization (distance); reflections esp. earphones improve distance judgement; may be more driven by monaural cues p. 458

• Image size and position; delayed lateral sound caused a “pleasant broadening of the primary sound source” (Haas)

• Sense of space; get multichannels

• Timbre: comb filtering, repetition pitch; “Two ears and a brain have advantages over a microphone and an analyzer” p. 459

• Timbre: audibility of resonances; don’t record acoustic music outdoors

• Speech intelligibility; very important freq. range

 

[krabapple]

is nice,

but who ever considers this path has without a doubt another preference then the mainstream.
it will hardly ever be close to a anaechoic chamber.

If you did the reading you would know the research does not discount 'another preference'. Indeed it traces the difference between typical listeners and professional sound engineers.


The person I replied to wrote "completely inert/dead ". Even fans of room treatments do not typically advocate that.

 

[dasdoing]

If you did the reading you would know the research does not discount 'another preference'. Indeed it traces the difference between typical listeners and professional sound engineers.


The person I replied to wrote "completely inert/dead ". Even fans of room treatments do not typically advocate that.

ok, but I doubt he meant it literaly.
I would love to hear a setup in an anaechoic chamber though. I am not sure I would dislike it. like he said, nobody ever complained about dead sound using a headphone. people mainly complain about strange feelings in dead-ish rooms. in my experience this is just a temporary feeling. my GF said she felt like "deaf" for the first week she entered my treated room. after a few days it was a totaly normal room for her

 

[MRC01]

Sorry to bump an old thread but I've been reading a lot about the how a room effects sound recently which lead me to here and I have to agree with you 110%, I believe a room should be completely inert/dead, I can hear the room in my sound, it really bothers me.
...

My preferences are similar. If the spectrum extremes are "dead" (anechoic chamber) and "live" (highly echoic, imagine a medium sized public restroom with tiled floors and walls), then I prefer a listening room on the "dead" side of the half-way point. Not totally dead, not anechoic, but less reverb/echo than most other people seem to like. I think "dry" is a better descriptor than "dead", since the latter sounds more extreme.

All recordings of acoustic music capture some amount of the room they are recorded in. Relatively less or more, depending on how close miced they are, among other factors. I want to hear what's in the recording, not my room. If the recording captured the hall (say, a singers recorded in a cathedral from medium distance), it should sound like I'm in the cathedral. If the recording was close-miced, it should sound unnaturally dry with some zing, like I'm on stage sitting with the musicians. I've experimented in various rooms with different levels of treatment and find that in either case, I prefer to have less, not more, of my own room's relections in the sound. I feel this gets me closer to the recording itself, revealing subtle clarity and detail that can be masked by overly reverberant rooms.

All that said, I'm not saying I prefer to listen in a completely dead room or anechoic chamber!

 

[Kal Rubinson]

All recordings of acoustic music capture some amount of the room they are recorded in. Relatively less or more, depending on how close miced they are, among other factors. I want to hear what's in the recording, not my room.

Toole, F. E. 2006. Loudspeakers and Rooms for Sound Reproduction—A Scientific Review J. Audio Eng. Soc., Vol. 54, No. 6 June
• Sense of space; get multichannels

 

[Wes]

Yes, I thought of you when I read that passage in their paper.

 

[eliash]

Besides Toole also stating that there are certain people who don´t like much "envelopment" (or ambient room sound, as I understand it), I guess with increasing age (could be inner ear/brain-processing related) I encountered the problem not to be able any more, masking 1st order room reflections completely, resulting in perceived distortion (or limited instrument´s resolution) in mid and higher frequency range.
Some wall treatment and stiff speaker setup (less bass-induced vibration on the midrange/tweeter) gained me some 5 years of additional listening pleasure until now...

 

[dasdoing]

not trying to discredit Harman/Toole, but I always feel like many hear treat it like a bible.
It is just one study, and a very subjective one

sorry for offtopic

 

[Kal Rubinson]

not trying to discredit Harman/Toole, but I always feel like many hear treat it like a bible.
It is just one study, and a very subjective one

Yes, although alternative references are always welcome.

 

[krabapple]

not trying to discredit Harman/Toole, but I always feel like many hear treat it like a bible.
It is just one study, and a very subjective one

sorry for offtopic

Dr. Toole's book -- and his paper cited above -- are reviews and summations of the research literature. They are not just about work Toole/Harman have done.

 

[dasdoing]

Dr. Toole's book -- and his paper cited above -- are reviews and summations of the research literature. They are not just about work Toole/Harman have done.

so it is a meta-study? if so, I didn't knew.
does the included research literature include significant study on treated rooms, though?

 

[Bjorn]

• Sense of space; get multichannels

Or use lateral later arriving diffuse energy if you have a dedicated room. Besides achieving spaciousness, you avoid the lobing and comb filtering added from multichannels. It's really much better but obviously few can do it. Commonly done in studios though.

 

[Bjorn]

so it is a meta-study? if so, I didn't knew.
does the included research literature include significant study on treated rooms, though?

No. It doesn't. And the Harman room with some treatment is quite poorly treated.

Studies have been conducted on treatment long before Toole, but they have been primarily focusing on accuracy. But with psycoacoustics in mind of course. For accuracy you would never leave the side walls untreated.

 

[krabapple]

so it is a meta-study? if so, I didn't knew.
does the included research literature include significant study on treated rooms, though?

"Loudspeakers and Rooms for Sound Reproduction—A Scientific Review" -- that was unclear?

A good review paper (and book) touches on all the relevant research on a topic and discusses common and conflicting conclusions therein. Dr. Tooles' reviews (and book) are good. Note that the paper is from 2006.

(Somewhat different from a meta-analysis -- that phrase has a particular meaning, for a paper reporting new statistical analysis on the combined results of older work, typically to glean significant trends hidden in the individual works).

 

[krabapple]

No. It doesn't. And the Harman room with some treatment is quite poorly treated.

Studies have been conducted on treatment long before Toole, but they have been primarily focusing on accuracy. But with psycoacoustics in mind of course. For accuracy you would never leave the side walls untreated.

The question of preference for treatments, specifically, is only an instance of the larger topic of preferred degree of reflected sound at the listening position. Treatments aren't the only thing that affect this. One need not study 'treatments' per se to get useful data (conclusions that could be applied to the use of treatments too).

The topic is treated in this chapter. Rigorous published research papers directly related to subjective evaluation of reflectivity are discussed at length in 7.4.1 through 7.4.4

Chapter 7: Above the Transition Frequency: Acoustical Events and Perceptions
1.    The Physical Variables: Early Reflections
    1.    Problems with the Stereo Phantom Center Image
2.    The Physical Variables: Loudspeaker Directivity
3.    The Physical Variables: Acoustical Surface Treatments
        1.    Absorbers
        2.    Engineered Surfaces and Other Sound Scattering/Diffusing Devices
4.    Subjective Evaluations of Physical Variations
        1.    Side Wall Treatment: Reflecting or Absorbing –Kishinaga et al. (1979)
        2.    The Effect of Loudspeaker Directivity – Toole (1985)
        3.    Loudspeaker Directivity and Wall Treatment Together – Choisel (2005)
        4.    The Nature of the Sound Field – Klippel (1990)
        5.    Observations of an Audio Enthusiast – Linkwitz (2007)
        6.    Observations of an Audio Enthusiast – Toole (2016)
        7.    Floor Reflections: A Special Case?
5.    Professional vs. Recreational Listening
    1.    Hearing Loss is a Major Concern
    2.    Discussion
6.    Perceptual Effects of Room Reflections
    1.    Adaptation and Perceptual Streaming
    2.    The Effect of Rooms on Loudspeaker Sound Quality
    3.    The Effect of Rooms on Speech Intelligibility
    4.    Sound Localization in Reflective Spaces − The Precedence (Haas) Effect
    5.    Bringing the Precedence Effect into the Real Acoustical World
        1.    Ceiling vs. Wall Reflections
        2.    Real vs. Phantom Images
        3.    Speech vs. Various Musical Sounds
7.    Meaningful Measurements of Reflection Amplitudes

Quote from this chapter:
"As I stated at the end of the earlier edition of this book, the treatment of early reflection boundary areas is "optional" : reflect, diffuse or absorb, as the customer prefers." --Sound Reproduction (3rd edition) [The suggested home theater layouts he illustrates later in his book include these optional treatments.]

But hey, feel free to write up your own review of the the literature and your own research, if you think you have a better handle on these topics (treatment, surround sound) than he does.

 

[Wes]

Review papers/books need to be updated periodically (tho no one has updated mine).

All in all, most rooms seem to not need much tmt. for reflections; however, I can say it is a bad idea to back up a Maggie panel into a corner formed by large glass windows...

 

[amirm]

Studies have been conducted on treatment long before Toole, but they have been primarily focusing on accuracy. But with psycoacoustics in mind of course. For accuracy you would never leave the side walls untreated.

Not at all. The latest research into this from McGill University was published in peer reviewed Journal of Audio Engineering Society: The Practical Effects of Lateral Energy in Critical Listening Environments
J. Audio Eng. Soc., Vol. 60, No. 12, 2012 December

This was a controlled, blind test of absorption, reflection and diffusion.

Subjects were professionals:

This was the final outcome as far as listener preference:

So the largest group preferred reflections for mixing. Absorption was third, slightly behind diffusion.

What is interesting here is that it was always thought that people producing music would want absorption/dead room. This research invalidates that.

 

[Bjorn]

The study "The Practical Effects of Lateral Energy in Critical Listening Environments" is a research on preferences and not accuracy. Secondly, preferences here will highly depend on exactly how you treat the room. In this case, some of the treatment was quite poor. Like it often is with these studies. For example: You don't use Skylines to treat side wall reflections.

There are multiple tests that people have done were they have come to a different conclusion than this. Basically, preferences will vary and doesn't give us objective results. Short listening tests with some type of music material doesn't necessarily give us the the answer to what we prefer over time either with different music material either. People should really experience for themselves.

There's not doubt that lateral reflections degrade areas like clarity, intelligibility, localizations and tonality to different degrees. That's well established. Whether people prefer something less accurate is another debate. But that obviously also depends on the acoustics of the rest of the room, which again is something this particular study didn't take into consideration at all. The fact that they measured the RT60 in a room where reverberation time or a diffuse sound field doesn't exist and which Toole also clear tell us, is quite humorous.

 

[amirm]

The study "The Practical Effects of Lateral Energy in Critical Listening Environments" is a research on preferences and not accuracy.

No at all. Even the abstract tells you otherwise:

And in the paper itself:

The "preference" was which setup they liked best for doing this work.