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ISO 226 Equal-Loudness-Level Contour Signal

version 1.0 (2.15 KB) by

Generates a psychoacoustic equal loudness contour (curve) as described in ISO 226.

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This function will return a 29-point equal loudness contour for your desired phon level. The frequencies evaulated in this function only span from 20Hz - 12.5kHz, and only 29 selective
frequencies are covered. This is the limitation of the ISO standard.

In addition the valid phon range should be 0 - 90 dB SPL. Values outside this range do not have experimental values and their contours should be treated as inaccurate.(Limitation due to standard)

If more samples are required you should be able to easily interpolate these values using spline().

*For more information regarding this method refer to ISO 226.

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Usage: [SPL FREQ] = ISO226(PHON);

PHON is the phon value in dB SPL that you want the equal
loudness curve to represent. (1phon = 1dB @ 1kHz)
SPL is the Sound Pressure Level amplitude returned for
each of the 29 frequencies evaluated by ISO226.
FREQ is the returned vector of frequencies that ISO226
evaluates to generate the contour.
------------------------------------------------------------

Comments and Ratings (31)

jing zhang

VPG

VPG (view profile)

Jeff Tackett

Jeff Tackett (view profile)

Hi Olivier, in order to understand the symbols you must purchase the publication of ISO226. This MATLAB function only implements the mathematics described there. But to summarize, dozens of loudness tests have been performed over the last ~80 years and this function fits a curve to all of these tables. If you read the paper many of your questions will be answered.

It's not precised in this script what is it ?about af, Lu, Tf, and Ln, , what are the symbol represented by af, Lu, Tf, and Ln? Where the vales come from (arbitrary or not) Tf af, Lu, Tf, and Ln : what is it ?

Radek

Radek (view profile)

I've upgraded a bit your function, now it accepts expressions like surf(iso226(20:10:80)) https://www.box.com/s/g1cdj6q30ho5w3gvt80j producing beautiful 2D map

harsh

harsh (view profile)

can anybody here tell me wat information we get from equal loudness curve?plz tell me. my Btech project is related to this?
i am also lookin to generate Masking Curves

harsh

harsh (view profile)

harsh

harsh (view profile)

harsh

harsh (view profile)

harsh

harsh (view profile)

harsh

harsh (view profile)

can anybody here tell me wat information we get from equal loudness curve?plz tell me. my Btech project is related to this?
i am also lookin to generate Masking Curves

Alex

Alex (view profile)

oddo

oddo (view profile)

here is a free excel file for loudness calculation:
www.noisestructure.com/products/Loudness.php

Alex Nieva

FXB

FXB (view profile)

So helpful. thx!

Hey guys, I tried running this script but it returns with an error message at line60. Could any of you guys give me some feedback on the problem.

For example i tried iso226 [52 63], and it returned that error message

Thanks

Germ

Germ (view profile)

Pradeep

It is not clear whether it is ISO 226 : 2003 or 1987 standard ?

Abbas Khudair Abbas

good job Jeff

Vincenzo Gambino

bo qin

a thousand thanks!

enrico cignoni

Pablo Henriquez

Great and usefull application. Thanks Jeff

Julien Riquelme

Very usefull to improve my audio mastering to improve the loudness of the CD... Thanks a lot !

Laurent SIMON

Very useful to me too... I lacked of something like this...

MarC .

Thank you. It was really useful for me.

Johannes Buechler

Neat implementation of the formula from ISO standart 226. Thanks a lot!

William Hooper

I agree with the earlier comments, that this is a welcome addition to the acoustic data information available on the internet.

. .

This code contains the only fee-free "nearly closed form" expression for the ISO curves I've been able to find online. Nice.

Christian Schultes

No running without the Communication Toolbox

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