Delay Time and Decay Time

[dallasjustice]

http://www.aes.org/tmpFiles/elib/20170305/18547.pdf

This open access paper appeared in the most recent AES journal. Delay time and decay times were tested using various genres and musical tempos (bpm). The theory is that longer delay and decay times are better suited to slower music and shorter ("dry") delay and decay times fit better with faster music.

Although there is some relationship with regard to delay times, the relationship seems more complex when it comes to decay times. There don't seem to be any definitive conclusions. But I did find it interesting that music with heavy syncopation were better received with less decay times. (More dry)

IMO, I think there's a fair range of acceptable RT and I DO believe musical genre preference influences which end of the acceptable RT one prefers.

Thoughts? Personal experiences?

 

[DonH56]

So the delay they are describing is for a delay line to recreate reverberation, not the time delay as I had first thought. Big difference!

Greater reverberation times and decay is often preferred for music and avoided for speaking. The classic example of a mixed-use venue is a church: a big, old gothic church with lots of reflective surfaces makes the choir sound great but the preacher hard to understand. Balance in all things...

It is more complicated for audio reproduction as you get into the debate about staying true to the source, keeping your listening room pretty dead so the only reverb is that which was encoded into the source, vs. a more "live" room that adds reverb to the source. And of course it is hard to say what the artist and/or sound engineers anticipated when they did the final mix... I generally prefer a "dead" room as the image is more stable, comb filter effects and such are suppressed, and the sound is enveloping enough for me as-is without the room contributing. I am in the minority, however.

I agree genre has an effect, along with a myriad of other variables...

 

[oivavoi]

Interesting. It's very much in line with my own experience and preferences. I prefer "dry" sound for fast studio music, and I prefer "wet" sound (lots of reflections etc) for symphonic music, slow music, etc. I therefore prefer to listen in the very near-field when listening to hiphop or metal for example, to get the sound to be as dry as possible. But for classical music, I often like to listen further away, to get a wetter and more encompassing sound.

Will read the paper also!

 

[RayDunzl]

So, this is a preference test for what's on or added to the recording, not what happens in a room.

I tend toward dry, as a general rule, I think.

Artificial enhancements are just that, and easily overcooked.

 

[dallasjustice]

Yes. But I think the assumption is that the artificial sound is comparable to the real thing. I think it's the only reasonable way to test this phenomenon. It doesn't seem feasible to test folks in different rooms with different delay or RT. There are too many other factors in such a case to invalidate the conclusion drawn therefrom.

So, this is a preference test for what's on or added to the recording, not what happens in a room.

I tend toward dry, as a general rule, I think.

Artificial enhancements are just that, and easily overcooked.

 

[Fitzcaraldo215]

Interesting. It's very much in line with my own experience and preferences. I prefer "dry" sound for fast studio music, and I prefer "wet" sound (lots of reflections etc) for symphonic music, slow music, etc. I therefore prefer to listen in the very near-field when listening to hiphop or metal for example, to get the sound to be as dry as possible. But for classical music, I often like to listen further away, to get a wetter and more encompassing sound.

Will read the paper also!

Your preferences make some considerable sense to me for stereo. They mirror somewhat the natural acoustics, miking and engineering of studio vs. concert hall recordings and, frequently, of pop vs. classical.

I, too, prefer listening further away as a primarily classical listener. But, I use discretely recorded Mch to deliver the reflected and reverberant effects of the venue. I find that trying to simulate or recreate the effects from stereo sources or via a two-channel system is just hopelessly inaccurate, though some might enjoy that. Given that I have a choice, I just do not find the tradeoff acceptable. I know better personally for my own purposes via my my own comparative listening.

 

[fas42]

My experience is that when a system is good enough then the delay and decay times of what's on the recording take over the acoustics of the listening area. That is, you can change where you listen to the playback and it always "sounds the same", irrespective - one's mind is compensating for room effects, automatically, and discarding local echos as not being relevant.

Which means that how it was recorded is everything - you're stuck with how the recording engineer wanted it. I generally find that they make good decisions, though I can think of one highly regarded audiophile label piano recording which is drowning in location reverb, and it sounds quite ridiculous, to my ears. Very fast tempo pieces seem to be well judged IME, and I can't think of a single example where mixing decisions really bug me. A "killer" album for having everything 'wrong' is a mariachi CD - this has lots of big band sound, uptempo, huge amounts of reverb applied in varying degrees to the various sections, lots of effects, very "brightly" recorded, no cut on the treble at their end, very dense, layered sound - this would be a nightmare on most 'audiophile' rigs, impossible to listen to.

 

[Blumlein 88]

The link in the OP is not working for me. This appears to be the same paper:

http://www.aes.org/e-lib/browse.cfm?elib=18547

 

[Blumlein 88]

I read their conclusions and results a bit differently. Decay or reverb times were not shown in this test to relate to tempo. Delay times were inversely related to tempo in terms of what listener panels preferred. Faster temp less delay is preferred.

Sort of makes sense that if you have too long a delay with rapidly proceeding beats of music it becomes muddled or muddied in a way that isn't enhancing anything.

 

[amirm]

Yes. But I think the assumption is that the artificial sound is comparable to the real thing. I think it's the only reasonable way to test this phenomenon. It doesn't seem feasible to test folks in different rooms with different delay or RT. There are too many other factors in such a case to invalidate the conclusion drawn therefrom.

The psychoacoustics of room reflections (i.e. RT60) and electronically generated ones are very different Michael. With room reflections the ears hear a differential signal due to direction of reflections. This doesn't happen when the reverberations come from the same speaker.

 

[ChrisH]

This actually make me think of large hall acoustics, where you try to balance the delay, reverb etc.. with the type of music that will be performed. If you have music that is more vertical, like Bach, you want a drier acoustic. Why is this? Because of the style of the music itself, and the acoustic space it was composed for. St. Thomas Church in Leipzig has a very small delay and reverb times. It's amazing for public speaking. It would not be good for a Mahler symphony; which is more horizontal. For Bach and his fugues and counterpoint it is exactly what you want. You can hear all of the lines speak clearly. Or maybe Bach wrote the music he did because of the acoustic space.

 

[STC]

______________________________________________________________

Newbie here. I am not in audio industry and a recovering audiophile. I am not sure whether I am qualified but I am here to learn and share and to give you guys to tease.

______________________________________________________________

Speaking from experience with 22 speakers for convolution for recreating acoustic space of a concert hall, I do agree that a shorter decay for strong center vocal emphasized audio. However, I don't think there is a clear answer for faster studio sound as described in post # 3.

It is more related to the size of the ensemble; a full orchestra with higher volume from the convoluted speaker and smaller ensemble requires lesser effect.

 

[Thomas savage]

______________________________________________________________

Newbie here. I am not in audio industry and a recovering audiophile. I am not sure whether I am qualified but I am here to learn and share and to give you guys to tease.

______________________________________________________________

Speaking from experience with 22 speakers for convolution for recreating acoustic space of a concert hall, I do agree that a shorter decay for strong center vocal emphasized audio. However, I don't think there is a clear answer for faster studio sound as described in post # 3.

It is more related to the size of the ensemble; a full orchestra with higher volume from the convoluted speaker and smaller ensemble requires lesser effect.

Welcome to ASR, thanks for taking the time to contribute

 

[Thomas savage]

No objective room measurments but when playing music with heavy, fast and repetitive symbol work ( like Russian circles- station) if my rooms too lively it's a total mess.. however it's a total mess when you see them live my room is fairly dead, the closed end is deader than the open end...

It's how I like it, no symbol mess no matter what's playing.. why would you want old sound bouncing about killing the new sound

 

[STC]

No objective room measurments but when playing music with heavy, fast and repetitive symbol work ( like Russian circles- station) if my rooms too lively it's a total mess.. however it's a total mess when you see them live my room is fairly dead, the closed end is deader than the open end...

It's how I like it, no symbol mess no matter what's playing.. why would you want old sound bouncing about killing the new sound

Thank you for your warm welcome.

The reason why we want sound bouncing off the wall is that's how we hear most musical performance.

The best experience would be in a venue with good acoustics and naturally those are always with longer reverberation time than our room.

Without knowing much about room acoustics, I thought by covering the room with rockwool would give me the true sound of the recordings without room colouration. I was wrong.

No matter how much room sound was recorded in the original sound, you still want the sound of the room to add coloration.

That's the reason I add the side convolution speakers bouncing off sound from many different angles.

ST

p.s. This forum is not mobile friendly! LOL. It is so difficult to type with the phone.

 

[Fitzcaraldo215]

Looks like the link to the original paper is now bad. I should have read it before shooting my mouth off in his thread, which I had not. Interesting thread, though,nonetheless. Thanks, @dallasjustice.

But, I will ramble on further, nonetheless. As we know from studying various room correction schemes, there is a difference in what is necessary and what we can or should do as a function of frequency. For example, bass below the transition frequency has room modal reflections that are detrimental. So, deadening the room for those and/or applying narrow band EQ centered at problem frequencies is often a good thing. I think most here agree with that. Might it be that the idealized total and complete suppression of reflected energy below the transition frequency would be a good thing if we could feasibly achieve it? We cannot get there, of course.

I think it is a different matter above the transition frequency where narrow band corrections are generally to be avoided. It is at these frequencies that we can make a room too lively, bright and reflective or too dead sounding, more on a wide frequency band basis. I think Amir has shown in one of his papers that the ear hears reflected energy differently at these frequencies, for example, in integrating and smoothing the perceived effects of some of the inevitable reflective comb filtering. It also appears per Amir we perceptually prefer reflections from vertical surfaces, within reason, but not from horizontal ones, which we tend to dislike. RT60, for example, does not appear to take that into account.

Meanwhile, I have no idea what the "right" delay and decay parameters are. I think I am with Ray in conceptually preferring a drier sound that is more about the recording and less about the room. But, having heard some over damped rooms filled to the brim with absorbers at an ASC dealership, I would not want to go there either.

PRAT also comes up frequently in some subjective reviews, though I cringe every time. It is a cool, hip concept in some circles that seems "more objective", but which is meaningless and has no metrics. My take on what those reviewers are actually hearing is perhaps just a subjectively "more likable" bass line, perhaps just a louder, stronger one delivered primarily by the rhythm instruments. You can tap your toes to it. So, it seems more about inroom bass frequency response, including room effects, hangover-prone or peaky though they might be in the hands of an audiophile who eschews measurements.

 

[RayDunzl]

Looks like the link to the original paper is now bad.

Go here

http://www.aes.org/e-lib/browse.cfm?elib=18547

Download Now

 

[RayDunzl]

I think I am with Ray in conceptually preferring a drier sound that is more about the recording and less about the room.

The paper, once you read it, is more about recording technique than rooms, and my comment was meant to infer that I think I tend to prefer a dry (nothing obviously added) recording, as my ear naturally listens for articulation and nuance in a player's performance, versus layering a Specter-esque 'Wall of Sound" over/behind whatever is being played.

Intro:
"It is a common belief that settings of artificial reverb and delay time in music production are strongly linked to musical tempo and related factors. But this relationship, if in existence, is not yet understood. We present the results of two subjective tests that evaluate user preference of young adults with formal training in audio engineering on artificial reverb and delay time, while trying to relate choice to tempo and other low-level explaining factors"

Certainly, pipe organs and choirs often perform in a reverberant space, and that is fine and natural, but when that choir performs in a studio, I can tire quickly of an imitation cathedral effect plopped on top of their singing.

As ever, I can be wrong or fooled, but I certainly don't add any "effects" here, and can be annoyed by those that have been.

 

[Fitzcaraldo215]

Ray - thanks for the link and the clarification.

To me, recording is a black art, and I give recording engineers considerable leeway in using their best judgement in deciding what the proper balance is. Like you, I conceptually prefer non-artificial means, but engineers live and die on the basis of how well we like the result, however achieved. Their job is to please you and me, the consumers. So, they should do whatever "works".

@dallasjustice accurately stated a key difference as to recorded genres. As a classical music afficianado, artificial effects are generally a no-no, at least if it makes their use in any way obviously audible. Classical music recording moved out of the studio into the concert hall long, long ago. And, there is plenty of natural reverb, decay, etc. in the hall. Artificial gimmicks are not really necessary. The art is to achieve some pleasing and desirable balance - plausibly - in the final result via mike placement, mixing, mastering, etc.

One reason for my preference of Mch over stereo for classical is that it attemps to preserve a plausibe spatial replica of the hall and the performers within it, a sonic image much as one experiences live. I listen almost exclusively to Mch, and I have not bought a CD or stereo recording in a decade. But, in my many stereo decades, I used to deplore closely miked recordings, especially piano, which were the rule, not the exception. Detail, yes, but too much. Spatial accuracy, none at all.

I do not know if that is still going on in stereo. (The classic example is Glenn Gould's incessant humming to the performance, brilliantly? captured by Columbia engineers ages ago, though it might not have been so obvious with the mikes further away. It's OK. I still love Glenn Gould. His recordings were all done in the studio, BTW.) However, my general impression for years now is that the closely miked piano, artificially miles wide in stereo, is a thing of the past in most Mch recordings in favor of a sonic image that much more closely resembles the perspective of the real thing live.

And, the thing about Mch when done well in classical - reduced/controlled listening room effects with natural, recorded hall acoustic in their place - is that, to me, it is the best game in town sonically and with no gimmicks. Stereo classical music recordings almost always attempt to bring some sense of the acoustic ambiance of the hall, its reverb, decay, etc. But, it is just an inaccurate one by comparison because it lacks suffient spatial dimensions.

I do not think the topics in this AES paper are really relevant to classical music recording. Just go down to your local symphony or chamber music in, hopefully a decent hall, concert to hear what it is supposed to sound like - a sonic reference. I am lucky, perhaps. I have the Philadelphia Orchestra in Verizon Hall, a world-class Chamber Concert series and numerous other local concerts in various venues. Many current Mch classical engineers get it. And, there are huge numbers of recordings that bear this out.

But, if there are things in the paper that will in some way help commercial pop engineers make better recordings, I am all for it, not that I would buy those recordings.

 

[dallasjustice]

I think there's considerable misunderstanding about this paper. Artificial delay and reverb is used in an experimental fashion using headphone simply to determine whether there's a preference depending on the genre and pace of the music. This has valid application in the real world. Maybe there's a better research design but I still haven't seen a better proposal to investigate this very valid question.

You refer to certain classical music venues as "reference." I listen to live classical music almost every week in the Meyerson here in Dallas. I've also heard other genre in the Meyerson. Classical music venues are NOT universally "reference" for all types of music. I've heard fast paced rhythmic jazz led by Doc Severson's awesome band in the Meyerson. The Meyerson's super long tails and delayed reflections off the canopy totally destroyed the rhythm. Doc's band would have been much better served in a smaller venue.

I think David Byrne explains the genre/venue matching issue better than anyone.

Ray - thanks for the link and the clarification.

To me, recording is a black art, and I give recording engineeras considerable leeway in using their best judgement in deciding what the proper balance is. Like you, I conceptually prefer non-artificial means, but engineers live and die on the basis of how well we like the result, however achieved. Their job is to please you and me, the consumers. So, they should do whatever "works".

@dallasjustice accurately stated a key difference as to recorded genres. As a classical music afficianado, artificial effects are generally a no-no, at least if it makes their use in any way obviously audible. Classical music recording moved out of the studio into the concert hall long, long ago. And, there is plenty of natural reverb, decay, etc. in the hall. Artificial gimmicks are not really necessary. The art is to achieve some pleasing and desirable balance - plausibly - in the final result via mike placement, mixing, mastering, etc.

One reason for my preference of Mch over stereo for classical is that it attemps to preserve a plausibe spatial replica of the hall and the performers within it, a sonic image much as one experiences live. I listen almost exclusively to Mch, and I have not bought a CD or stereo recording in a decade. But, in my many stereo decades, I used to deplore closely miked recordings, especially piano, which were the rule, not the exception. Detail, yes, but too much. Spatial accuracy, none at all.

I do not know if that is still going on in stereo. (The classic example is Glenn Gould's incessant humming to the performance, brilliantly? captured by Columbia engineers ages ago, though it might not have been so obvious with the mikes further away. It's OK. I still love Glenn Gould. His recordings were all done in the studio, BTW.) However, my general impression for years now is that the closely miked piano, artificially miles wide in stereo, is a thing of the past in most Mch recordings in favor of a sonic image that much more closely resembles the perspective of the real thing live.

And, the thing about Mch when done well in classical - reduced/controlled listening room effects with natural, recorded hall acoustic in their place - is that, to me, it is the best game in town sonically and with no gimmicks. Stereo classical music recordings almost always attempt to bring some sense of the acoustic ambiance of the hall, its reverb, decay, etc. But, it is just an inaccurate one by comparison because it lacks suffient spatial dimensions.

I do not think the topics in this AES paper are really relevant to classical music recording. Just go down to your local symphony or chamber music in, hopefully a decent hall, concert to hear what it is supposed to sound like - a sonic reference. I am lucky, perhaps. I have the Philadelphia Orchestra in Verizon Hall, a world-class Chamber Concert series and numerous other local concerts in various venues. Many current Mch classical engineers get it. And, there are huge numbers of recordings that bear this out.

But, if there are things in the paper that will in some way help commercial pop engineers make better recordings, I am all for it, not that I would buy those recordings.