Equal loudness curve

kensuguro · Post by **kensuguro** » Sat Jun 01, 2002 12:22 pm

Nothing special really.. The equal loudness curve is derived from the fact that the shape of the ear resonates a specific frequencies, and thus becomes a filter of some sort. (the psycho acoustic portion might be ignored)

Check it out:

The curve means, if you apply this curve to a level sound, the loudness will be the same throughout the spectrum. For example, if you had a sine doing a rising up through the entire range, if you apply this curve, you're supposed to get a flat response. Though I'm not sure if psychoacoustical elements are considered in this compensation. But it's worth a try and it could be fun.

Anyway, I a few of the lines of this chart converted to Pulsar format, in stm2448 and for those who don't have the propack, the peq4. You can get them at
http://www.planetz.com/forums/viewtopic ... forum=13&0
Would anyone know if this chart is just about the biophysical characteristics of the ear and the cannal, or if it also considers phsychoacoustics?

Fede · Post by **Fede** » Sat Jun 01, 2002 1:05 pm

I've recently attended a class of applied acoustics at my university, there it has been said "they are curves of equal perception" not measurement of how ear modifies sounds: so I presume it's about psychoacoustics, but I'll check anyway soon by studying to sit that exam..

kensuguro · Post by **kensuguro** » Sat Jun 01, 2002 1:25 pm

cool. please fill us in if you find any info.

spacef · Post by **spacef** » Sun Jun 02, 2002 11:56 am

If that's the response of the human ear to the same sound at different levels (yes?) I understand the chart as showing that at different levels bass and trebles will be heard differently.
So may be it shows where compensation has to be made to allow medium frequencies to be heard, while bass & trebles do not blur everything. i don't know I 've looked for things on the web and didn't find much.

that's may be the closest subject i found

The Fletcher effect is mainly of comparing the difference between silent levels and loud levels. It is lot more diffucult to hear the bass frequencies at low levels. The listening level determines how you percieve the frequency balance. The great challenge is to judge, how much bass energy is the correct amount of energy for the mix.

on this post (by sunshine)
http://www.planetz.com/forums/viewtopic ... 5&start=20

i guess it's related. I feel i would use the contrary curve in an Eq (the graph in relation to decibel). just an idea from the curve. i'll try that soon i think.

[ This Message was edited by: spacef on 2002-06-02 13:17 ]

spacef · Post by **spacef** » Sun Jun 02, 2002 1:26 pm

http://hyperphysics.phy-astr.gsu.edu/hb ... tml#soucon

there's a lot of things, may be it helps

kensuguro · Post by **kensuguro** » Sun Jun 02, 2002 6:06 pm

hehe, that's where I got the graph from.

spacef · Post by **spacef** » Sun Jun 02, 2002 10:01 pm

Hehe,

But i still didn't find an answer to the question.

Do you think you're graph is helpful in mastering a track for live purpose ? that's what i'm into right now......

spacef · Post by **spacef** » Mon Jun 03, 2002 11:49 pm

http://www.jblpro.com/pub/manuals/pssdm_1.pdf

Immanuel · Post by **Immanuel** » Tue Jun 04, 2002 8:30 am

I have not studied the links, but I am quite possitive the curve shows, at what levels hte (average) ear will hear what frequencies this loud. Am I making myself unclear?

Take the low curve, it shows, that to hear a 20Hz tone, the volume needs to be close to 80db, where as to hear a 4000Hz tone below 0dB is enough (0dB is not silent by the way).

You can also see, that at low volumes the low bass and high treble will be relatively anonymous, where as at high volumes the low bass and high treble will be more present.

For this reason adding loudness to your mix will make the listener believe your music is played louder than it actually is. The (tweaked) relative frequency proportions experienced are equal to the (natural) relative frequency proportions experienced from the same music played louder.

I hope this is clear.

Immanuel

kensuguro · Post by **kensuguro** » Wed Jun 05, 2002 5:07 am

yeah, just so that no one gets the wrong idea, here's how the graph is read. (I think most of you understand it anyway)

The middle line, of 1k I believe, is the initial point of measurement. So, the most bottom line would mean "if a 1k sound is 10db, for a 100hz sound be percieved as the same loudness, it would have to be 30db". And then so on. (so everythone lying on the line labeled "10" would be percieved as 10db)

So if you have a white noise, with the 1k zone measureing 10db, when you apply the 10db line on the white noise, it would appear to have equal loudness in all spectral zones.

About spacef's question, I'm not sure if the specific curve will help in mastering. This is because the curves are meant to be used on sounds with equal energy spread (like white noise) and the more unequal the original material is, the further away you go from these curves.

For instance, if the original material naturally creates this curve, you won't need to apply anything for all spectral zones to sound equal. But a mix with all spectral zones having the same loudness is quite boring so you'd want to keep away from that.
And about whether or not these curves consideres psychoacoustical aspects, the answer was yes . The experiment was simple. People were played tones of different frequencies and then were asked to adjust the volume to make everything sound equally loud. So I guess everything from the biophysical aspects to psychoacoutic aspects are included in this experiment. The curve seems to be derdived from averaging out tons of these experiments.

[ This Message was edited by: kensuguro on 2002-06-05 06:08 ]

Fede · Post by **Fede** » Wed Jun 05, 2002 4:04 pm

a mix with all spectral zones having the same loudness is quite boring so you'd want to keep away from that.

hmm, imho a mix with spectrum freqs having the same loudness (perceived) should result in the optimal perception of all instruments and sounds: no sound/harmonics masking (however the difficulty is to decide what curve/volume to use for people to listen)

kensuguro · Post by **kensuguro** » Wed Jun 05, 2002 7:21 pm

well, I meant sort of like if it was inanimate at all.. ya know.. like totally FLAT throughout the song.

I won't make a new post for this.. stratofede, seriously, you gotta be misunderstanding me. Sure, the "general" curve should generally remain throughout the tune.. but then there are some contrasts within the piece, like the bass goes away at times, the highs go away at times... everything being there the entire time at the same volume obviously is not too artistic. Oh well, I think you get my point anyway.

[ This Message was edited by: kensuguro on 2002-06-06 06:46 ]

Fede · Post by **Fede** » Thu Jun 06, 2002 12:11 am

I think that kind of flatness is the conditio sine qua non to obtain a good mix that sounds good on every audio system. In my experience all good mixes remembered more or less those curves, I intend that when some freq bands are louder than others it's easy listener gets annoyed from this. But this is only my opinion...

[ This Message was edited by: StratoFede on 2002-06-06 01:12 ]

Post by **garyb** » Thu Jun 06, 2002 9:29 pm

it's about percieved loudness of specific freqs at specific db.it shows the ear to be more sensitive to some freqs at low volumes than at high volumes in relation to the rest of the spectrum.it shows why the "loudness" button on some stereos works the way that it does(adding lows at low volumes sounds "flat" but the effect diminishes as volumes rise) also more importantly, it shows how one can be fooled when mixing by the volume that one mixes at.

Nestor · Post by **Nestor** » Fri Jun 07, 2002 7:35 pm

This topic sounds rather complicated. I really enjoy myself reading this, and the links are great, but it’s much more than what my music needs. I think that in a practical go, my ear is going to give me the information I need. Of course, for those of you building up devices it are a different matter, cos you need to deeply and fully understand it.

Post by **garyb** » Fri Jun 07, 2002 10:37 pm

this is on of the first lessons taught in any audio engineering program.....

spiderman · Post by **spiderman** » Fri Jun 14, 2002 5:49 am

I don't think it's very usefull in mastering since in the mixing process naturally we made this kind of compensation . this is just the mixing process . anyway it's usefull to correct the frequency response related to the level of listenning . so maybe it's possible to do a device which apply this kind of compensation following the master fader .then the frequencies curve remain flat at any level correcting the ears sensibility ....

spacef · Post by **spacef** » Wed Jun 19, 2002 1:18 am

I just released a device on spacef that alows you to play with those curves and acoustic effects, not with a single pot yet, but i think it's worth trying ... some of you might be interested
http://www.spacef.com

at0m · Post by **at0m** » Wed Sep 18, 2002 8:46 am

Funny nobody mentioned dB(A)-dB difference. dB(A) is never measured, but it's derived from the dB using the scale posted by Ken.

dB(A) is dB(perceived). Real low subs and very high freqs are sometimes inaudible or 0 dB(A), even at high dB.

The human earing works best at the frequencies we use most, that is around the human voice: 800-2400Hz or something. Other freq's are less life-important to us, there's no good receptors for that in our ear.

A DC signal for example is inaudible, but still shows it's dB (offset to X-axis) on VU meters. Most analog mixers have a condensor or so to filter DC or too low freqs - the condensers are 'speaker savers'.

Imagine having dB(A) approx. meters on SFP mixers, life would be so easy. But also, I think the meters would use much more cpu/dsp cycles.

kensuguro · Post by **kensuguro** » Thu Sep 19, 2002 3:24 pm

that would be an interesting device to have. I wonder how it'll work though.. (dunno the details about the db(A) thing)