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Author Topic: aural distortion  (Read 1401 times)

Keith Giles

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aural distortion
« on: January 26, 2020, 04:38:17 pm »

Some years ago I ran live sound regularly for a very loud death metal band; the kind of band where the lead vocalist does a lot of literal screaming. The drums were loud, the amplifiers louder. Getting vocals up and over the instruments was possible, but understanding the words was not. What I heard was distortion in the vocal range, especially in the frequencies where consonants lie. Until I put ear plugs in. I could hear every word. I was shocked. I thought the distortion was coming from the inability of my system to handle the high SPLs in that frequency range. What I discovered was that it wasn't the system that was distorting, it was my ears. When I did a little research I found an article that described what I was experiencing. That our hearing is prone to distortion at high SPLs and disproportionally so in the frequency range of 2 khz to 6 khz. This is more than the Fletcher-Munson curve we all know about although it is obviously related. I have tried to revisit this information, but I simply can't seem to find anything. I would appreciate any information or sources the forum can help me find to explore this idea more fully.
Thanks!
« Last Edit: February 03, 2020, 07:30:02 pm by Keith Giles »
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Steve-White

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Re: aural distortion
« Reply #1 on: January 27, 2020, 12:44:56 am »

Interesting.  No doubt the ears overload at some point.  Mine ring 24/7 from past stupidity.  Too many nights in clubs playing rock at 112-113db on the dance floor - at least that's what a fellow engineer claimed we were doing - I never measured it - he owned a studio and was probably right.

At at those levels, to me it was still intelligible - but in your face loud.
« Last Edit: January 27, 2020, 02:33:41 pm by Steve-White »
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Jean-Pierre Coetzee

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Re: aural distortion
« Reply #2 on: January 27, 2020, 04:23:07 am »

I find my right year distorts well before my left year, some 10dB or so. Usually at around 4k but can also happen at 800. I think it is quite dependent on individuals but definitely I prefer to listen to loud shows with plugs in. I rarely mix with plugs in but definitely like to reference a difficult mix with plugs in, like studio engineers will reference at lower volumes, can't do that live but can put in plugs.
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John Roberts {JR}

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Re: aural distortion
« Reply #3 on: January 27, 2020, 09:12:18 am »

I too have noticed distortion in one ear... Never a healthy sign, I have avoided loud sounds ever since getting out of the army.

JR
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Russell Ault

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Re: aural distortion
« Reply #4 on: January 27, 2020, 10:22:52 am »

Well, I guess it's not just me. I figured out in high school that my hearing (which otherwise tests out fine) would start to distort at fairly modest volumes (lower, I'm assuming, than most people). It's one of the reasons I don't do much rock and roll (and why, when I do, I consistently mix with plugs in).

-Russ
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Art Welter

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Re: aural distortion
« Reply #5 on: January 27, 2020, 10:34:40 am »

Some years ago I ran live sound regularly for a very loud death medal band; the kind of band where the lead vocalist does a lot of literal screaming. The drums were loud, the amplifiers louder. Getting vocals up and over the instruments was possible, but understanding the words was not. What I heard was distortion in the vocal range, especially in the frequencies where consonants lie. Until I put ear plugs in. I could hear every word. I was shocked. I thought the distortion was coming from the inability of my system to handle the high SPLs in that frequency range. What I discovered was that it wasn't the system that was distorting, it was my ears. When I did a little research I found an article that described what I was experiencing. That our hearing is prone to distortion at high SPLs and disproportionally so in the frequency range of 2 khz to 6 khz. This is more than the Fletcher-Munson curve we all know about although it is obviously related. I have tried to revisit this information, but I simply can't seem to find anything. I would appreciate any information or sources the forum can help me find to explore this idea more fully.
Thanks!
Keith,

About 10 days ago did some research along the same lines of questioning, found this report:

https://www.thecre.com/sefReports/wp-content/uploads/2012/12/Melnick-Human-temporary1.pdf

Years ago, while conducting HF driver tests, I thought that their distortion at high levels sounded quite horrible, though after listening to recordings of their performance at low level, seems most of the discomforting distortion was in my own hearing response- there is a fairly hard SPL limit in the upper range that sounds bad whether clean or distorted when my ears are “fresh”.

The sensation at louder levels which seems contrary to the equal loudness contours that flatten out with increased SPL may be due to the manner in which hearing TTS (temporary threshold shift) occurs.
TTS is the reduced sensitivity to noise after exposure to loud noise, it’s temporary effect diminishes after time in a quiet environment.
Evidence of TTS is apparent when you get into your car the morning after coming home from a loud concert the night before,  then must turn the stereo down to half the level that seemed “normal” the night before.

William Melnick has presented some evidence that indicates TTS is less when exposed to loud low frequency <125 Hz than higher frequencies.
With loud music played back with a low frequency “haystack” of +10 dB or more below 125Hz, the TTS threshold won’t “kick in” as hard, fast or with as deep of a reduction as it would from the same SPL at high frequencies. Most ear plugs don't do much attenuation in the low frequency, but can reduce TTS.
TTS is like high-frequency hearing loss, which affects the perception of speech sounds that have mostly high-frequency (2000–10000 Hz) energy, such as fricative consonants.
 
Looking at Melnick’s charts, we see as much as 20dB shifts from 95 dB SPL of 1.4-2kHz noise, while increasing the level to 108 dB with 500-710Hz noise reduces TTS to about 10dB. The range at which TTS between subjects is also quite a lot, so “too loud” is very subjective.

The decay time from TTS can be as much as 24 hours, it can be quite a while before your hearing normalizes after exposure to loud music or noise, what sounded good (or bad..) yesterday might be quite different after a break, and at a different level.

Art
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Mark Wilkinson

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Re: aural distortion
« Reply #6 on: January 28, 2020, 09:40:50 am »

Good stuff Art, thx.
Per recent discussions of the DIY forums, you know this spectral tilt /  harness  issue with increased SPL, has been a bug up my butt.
I really thought the rapidly increasing THD i measured with the 2 compression drivers i tested was at the root, but your well done compression driver tests put a rethink on that.

About the only stones i still want to turn over before i just say TTS is the cause (which my hunch is, that it is)
are a desire to normalize the Fletcher -Munson curves to about 2 or 3kHz, to make sure i really understand the implied overall spectral tilt around the most sensitive  frequencies.
And not to cast doubt on your tests, but i've recently learned how the mp3 process has a bigger problem with transient waveforms than i realized...that it can kinda squash various levels of dynamics into sounding the same..don't know if that could be a factor in your tests??? i tried to find the original recording online for a baseline....but no luck.

Anyway, thx again...
An aside ....The real impetus behind my desire to know about ear pain with SPL, is we have a super local venue that seats a few hundred.  Great acoustics, fine artists coming through regularly, but bleeding sound once the system is turned up. I've always attributed it to the 3-box vrx932 per side, because i've measured that i listen to my gear quite a bit louder without ear pain.  More than once i've thought about presenting them with an earnest plea, asking them to upgrade their mains. I don't want to be an ass, especially if it's not about the vrx....
But this TSS stuff has me thinking maybe immediate pain is more about the duration of SPL, in the same way permanent ear damage is.
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Jean-Pierre Coetzee

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Re: aural distortion
« Reply #7 on: January 31, 2020, 02:30:51 am »

Anyway, thx again...
An aside ....The real impetus behind my desire to know about ear pain with SPL, is we have a super local venue that seats a few hundred.  Great acoustics, fine artists coming through regularly, but bleeding sound once the system is turned up. I've always attributed it to the 3-box vrx932 per side, because i've measured that i listen to my gear quite a bit louder without ear pain.  More than once i've thought about presenting them with an earnest plea, asking them to upgrade their mains. I don't want to be an ass, especially if it's not about the vrx....
But this TSS stuff has me thinking maybe immediate pain is more about the duration of SPL, in the same way permanent ear damage is.

This is definitely biased since I know there are forums members here that will say the vrx series can sound good but I honestly have never heard a vrx system sound good.
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Keith Giles

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Re: aural distortion
« Reply #8 on: February 03, 2020, 08:01:56 pm »

Keith,

About 10 days ago did some research along the same lines of questioning, found this report:

https://www.thecre.com/sefReports/wp-content/uploads/2012/12/Melnick-Human-temporary1.pdf

Years ago, while conducting HF driver tests, I thought that their distortion at high levels sounded quite horrible, though after listening to recordings of their performance at low level, seems most of the discomforting distortion was in my own hearing response- there is a fairly hard SPL limit in the upper range that sounds bad whether clean or distorted when my ears are “fresh”.

The sensation at louder levels which seems contrary to the equal loudness contours that flatten out with increased SPL may be due to the manner in which hearing TTS (temporary threshold shift) occurs.
TTS is the reduced sensitivity to noise after exposure to loud noise, it’s temporary effect diminishes after time in a quiet environment.
Evidence of TTS is apparent when you get into your car the morning after coming home from a loud concert the night before,  then must turn the stereo down to half the level that seemed “normal” the night before.

William Melnick has presented some evidence that indicates TTS is less when exposed to loud low frequency <125 Hz than higher frequencies.
With loud music played back with a low frequency “haystack” of +10 dB or more below 125Hz, the TTS threshold won’t “kick in” as hard, fast or with as deep of a reduction as it would from the same SPL at high frequencies. Most ear plugs don't do much attenuation in the low frequency, but can reduce TTS.
TTS is like high-frequency hearing loss, which affects the perception of speech sounds that have mostly high-frequency (2000–10000 Hz) energy, such as fricative consonants.
 
Looking at Melnick’s charts, we see as much as 20dB shifts from 95 dB SPL of 1.4-2kHz noise, while increasing the level to 108 dB with 500-710Hz noise reduces TTS to about 10dB. The range at which TTS between subjects is also quite a lot, so “too loud” is very subjective.

The decay time from TTS can be as much as 24 hours, it can be quite a while before your hearing normalizes after exposure to loud music or noise, what sounded good (or bad..) yesterday might be quite different after a break, and at a different level.

Art

Hi Art,

Thanks for your detailed response. The idea that the presence of low frequency content makes hi SPL upper frequency content more tolerable is fascinating isn't it? What marvelous creatures we are!
I think I'm hopeful that there is a common experience amongst us; that when music is heard at a SPL greater than a certain level, clarity disappears. I'm sure that whatever level that is it varies among individuals and is affected by other variables such as TTS and the rest of the harmonic content. I'd love to be able to say "Don't bother listening at "X-SPL" because you won't understand the words anyway"!

I have another anecdote that might also be germane.

We have all had the experience of trying to communicate with someone in the middle of a loud show. In order to be heard, a person leans in close to our ears and shouts. OMG this hurts! (Probably dangerous). And it might take several tries to understand what the person is trying to say. So, I was at this loud show and a woman wanted to tell me something. As I leaned my ear toward her she did something very bold. She reached her hand to the side of my face and pressed the tragus (outer ear flap . . . I'm not that smart, I looked it up) closed with her finger and shouted right up against my ear. I heard every word. It didn't hurt. And I was blown away by how effective it was.

What I remember originally reading was, I believe, from an an audiologist reference. I sure wish I could find that and stop thinking I imagined it!

Thanks again.
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Keith Giles

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Re: aural distortion
« Reply #9 on: February 03, 2020, 08:12:06 pm »

Well, I guess it's not just me. I figured out in high school that my hearing (which otherwise tests out fine) would start to distort at fairly modest volumes (lower, I'm assuming, than most people). It's one of the reasons I don't do much rock and roll (and why, when I do, I consistently mix with plugs in).

-Russ

Nice to find another human with a similar experience. Like you, my hearing is pretty healthy. The distortion I hear in the vocals at very high SPLs is very similar to the sound you might hear from high distortion devices like a piezo tweeter. I've had the experience of having an inner ear infection during which loud sounds distorted and almost rattled. This is not that.
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Chris Grimshaw

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Re: aural distortion
« Reply #10 on: March 16, 2020, 04:55:25 am »


We have all had the experience of trying to communicate with someone in the middle of a loud show. In order to be heard, a person leans in close to our ears and shouts. OMG this hurts! (Probably dangerous). And it might take several tries to understand what the person is trying to say. So, I was at this loud show and a woman wanted to tell me something. As I leaned my ear toward her she did something very bold. She reached her hand to the side of my face and pressed the tragus (outer ear flap . . . I'm not that smart, I looked it up) closed with her finger and shouted right up against my ear. I heard every word. It didn't hurt. And I was blown away by how effective it was.

What I remember originally reading was, I believe, from an an audiologist reference. I sure wish I could find that and stop thinking I imagined it!

Thanks again.

I usually do something similar - shout just behind their ear. Works every time.

FWIW, I find my ears also get quite distort-y at high SPLs, and will often sit in the car with earplugs in and the radio on before what I know will be a loud show.
Listening to the radio with earplugs allows my hearing to re-calibrate to what sounds good (or at least balanced) with earplugs in, and I can mix pretty well during the show.

Chris
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Re: aural distortion
« Reply #10 on: March 16, 2020, 04:55:25 am »


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