Question about FR graphs
May 4, 2010 at 12:34 AM Thread Starter Post #1 of 11

hans030390

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When people measure the frequency response of something and put it in a graph, do they usually account for the fact that the human ear doesn't hear every frequency at the same loudness? I was just looking at the equal-loudness contour graphs, so that's why I'm asking.

I'm sure this has been asked before, and I'm sure there's a simple answer to it.
 
May 4, 2010 at 5:21 AM Post #3 of 11
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For the Headroom graphs and subsequently Tyll's new measurement lab, yes. The test ear has FR measurements against which the headphone measurements are compensated.
 
May 4, 2010 at 5:39 AM Post #4 of 11

Shark_Jump

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God I love a good graph.
File:Lindos4.svg

<Edit Hell what on earth is an svg file, i thought it was a jpg, goddam wikipedia, here is a good honest australian website>
ISO226.png


There are international standards commonly applied in the electronics/audio industry. Is this what you are after?

Have a look at this for a start.
A-weighting - Wikipedia, the free encyclopedia

A-weighting is the most commonly used of a family of curves defined in the International standard IEC 61672:2003 and various national standards relating to the measurement of sound pressure level (as opposed to actual sound pressure).[dubious – discuss] The others are B, C, D and now Z weightings (see below).

The curves were originally defined for use at different average sound levels, but A-weighting, though originally intended only for the measurement of low-level sounds (around 40 phon), is now commonly used for the measurement of environmental noise and industrial noise, as well as when assessing potential hearing damage and other noise health effects at all sound levels; indeed, the use of A-frequency-weighting is now mandated for all these measurements, although it is badly suited for these purposes, being only applicable to low levels so that it tends to devalue the effects of low frequency noise in particular [1].

A-weighting is also used when measuring noise in audio equipment, especially in the U.S.A. In Britain, Europe and many other parts of the world, Broadcasters and Audio Engineers more often use the ITU-R 468 noise weighting, which was developed in the 1960s based on research by the BBC and other organizations. This research showed that our ears respond differently to random noise, and the equal-loudness curves on which the A, B and C weightings were based are really only valid for pure single tones
 
May 4, 2010 at 10:50 AM Post #5 of 11

Feanor

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I think he was referring to the curves found on this page...

edit : well **** me these are basically the inverse of what you linked in, meh.
edit#3: and now this ^ makes no sense as you edited too... ah well

edit #2: this has interested me as well, it would be interesting to have FR measurements that are conducted at a fair number of sound levels, equalized by both the ears response and the equal loudness curves.
 
May 4, 2010 at 12:41 PM Post #6 of 11

Tyll Hertsens

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Quote:

Originally Posted by hans030390 /img/forum/go_quote.gif
When people measure the frequency response of something and put it in a graph, do they usually account for the fact that the human ear doesn't hear every frequency at the same loudness?


No. No need.

One hopes that the recording engineers used there ears well and mixed the music for the desired balance. Once they make that determination the job of the electronics is to be flat so that the proportions of bass and treble remain the same until it reaches the ears.

The only usefulness at the point of the Fletcher-Munson curves is if you are reproducing the sound at a different volume than the engineers were mixing it at. If you listen much loer, you should dial in some "loudness curve" to boost the lows and highs a bit.
 
May 4, 2010 at 2:30 PM Post #7 of 11

chinesekiwi

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You must factor it in the effect of the pinna as well, particularly with headphones (i.e. HRTF's). Flatline, which is ideal for speakers for neutrality, is not ideal for headphones.

Here's a sample graph of what the ears actually receive due to the shape of the pinna

HRTF_fb.gif


Note that the scale used is different from Headroom's. Anything below those ideals = recessed, above it = overemphasised.
Also you cannot compare (fairly) the frequency response of in-ears, headphones and speakers to one another due to this as of course in-ears for example, bypass the pinna.
You can only compare in-ears to in-ears, headphones to headphones and speakers to speakers.
Also with frequency response graphs, when people compare sound, it's usually how the different frequencies relate to one another rather than what line is higher, lower etc...
 
May 6, 2010 at 12:46 PM Post #8 of 11

hans030390

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Quote:
Quote:

Originally Posted by hans030390 /img/forum/go_quote.gif
When people measure the frequency response of something and put it in a graph, do they usually account for the fact that the human ear doesn't hear every frequency at the same loudness?


No. No need.

One hopes that the recording engineers used there ears well and mixed the music for the desired balance. Once they make that determination the job of the electronics is to be flat so that the proportions of bass and treble remain the same until it reaches the ears.

The only usefulness at the point of the Fletcher-Munson curves is if you are reproducing the sound at a different volume than the engineers were mixing it at. If you listen much loer, you should dial in some "loudness curve" to boost the lows and highs a bit.



Ah, I didn't really think about this, despite that being fairly obvious.
 
Quote:
You must factor it in the effect of the pinna as well, particularly with headphones (i.e. HRTF's). Flatline, which is ideal for speakers for neutrality, is not ideal for headphones.

Here's a sample graph of what the ears actually receive due to the shape of the pinna

HRTF_fb.gif


Note that the scale used is different from Headroom's. Anything below those ideals = recessed, above it = overemphasised.
Also you cannot compare (fairly) the frequency response of in-ears, headphones and speakers to one another due to this as of course in-ears for example, bypass the pinna.
You can only compare in-ears to in-ears, headphones to headphones and speakers to speakers.
Also with frequency response graphs, when people compare sound, it's usually how the different frequencies relate to one another rather than what line is higher, lower etc...


Interesting. Thanks for that info!
 
May 6, 2010 at 1:31 PM Post #9 of 11

MrGreen

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Quote:
You must factor it in the effect of the pinna as well, particularly with headphones (i.e. HRTF's). Flatline, which is ideal for speakers for neutrality, is not ideal for headphones.

Note that the scale used is different from Headroom's. Anything below those ideals = recessed, above it = overemphasised.


In terms of in-ears, Etymotic use a different curve (cant remember the name of it, but its on their site Diffuse Field, or something), and I am inclined to agree with them based on their sound.
 
May 6, 2010 at 1:53 PM Post #10 of 11

Tyll Hertsens

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Quote:
 

In terms of in-ears, Etymotic use a different curve (cant remember the name of it, but its on their site Diffuse Field, or something), and I am inclined to agree with them based on their sound.

Fortunately for the folks that make IEMs, they don't have to deal with the added complication of the folds and reflections of the pinna (outside part of the ear). Full sized headphones get some of these reflections, and they come in a flavor that doesn't occur naturally (since the close coupling of an earcup is unlike sound aproaching the ear from a normal source in the far-field).
 
I agree that Etymotic has this stuff dialed.  What most folks don't know is that Etymotic has a somewhat special way to calibrate their cans at 10kHz and above (using a Zwislocky coupler) and their IEMs perform better in the highs than most, IMHO.
 
 

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