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From: snickell on 27 May 2010 15:04
I'm trying to A/B test a filter, and I'd like to control for the human
preference for louder signals. Is there a standard way to do this?
Right now I'm normalizing to the avg RMS level of the a-weighted
signal. I'm hoping to achieve two signals with the same subjective
loudness so there's no 'louder signal' bias.

I'm a-weighting the signal before measuring the RMS in an attempt to
compensate for reduced sensitivity to low/high frequencies (as the
filter dramatically alters the spectral content it seemed like
normalizing to the straight RMS might still result in a different
subjective loudness... e.g. if the two signals had the same avg power,
but in one the energy went into 1khz and in the other the energy went
into 40Hz?).

Does this approach make sense to other people? Is there a better one?

thanks,

-Seth
From: Andrew Reilly on 27 May 2010 21:08
On Thu, 27 May 2010 12:04:04 -0700, snickell wrote:
[a-weighting RMS power to make equal loudness]
> Is there a better one?

Officially, ITU-R BS.1770 is supposed to be a better measure of loudness
than A-weighting.

There are some links to useful papers in this discussion:
http://www.hydrogenaudio.org/forums/lofiversion/index.php/t47154.html

Cheers,

--
Andrew
From: glen herrmannsfeldt on 27 May 2010 22:22
Andrew Reilly <areilly---(a)bigpond.net.au> wrote:
> On Thu, 27 May 2010 12:04:04 -0700, snickell wrote:
> [a-weighting RMS power to make equal loudness]
>> Is there a better one?

> Officially, ITU-R BS.1770 is supposed to be a better measure of loudness
> than A-weighting.

> There are some links to useful papers in this discussion:
> http://www.hydrogenaudio.org/forums/lofiversion/index.php/t47154.html

The wikipedia page tell some of the problems with A weighting,
though not so much for solutions.

I was just wondering, if you take two similar but different audio
signals and switch between them at, say, 1kHz, how the sound
changes with relative amplitude. Assuming no definite phase
relationship between the two.

-- glen
From: steveu on 27 May 2010 22:56
>Andrew Reilly <areilly---(a)bigpond.net.au> wrote:
>> On Thu, 27 May 2010 12:04:04 -0700, snickell wrote:
>> [a-weighting RMS power to make equal loudness]
>>> Is there a better one?
>
>> Officially, ITU-R BS.1770 is supposed to be a better measure of loudness

>> than A-weighting.
>
>> There are some links to useful papers in this discussion:
>> http://www.hydrogenaudio.org/forums/lofiversion/index.php/t47154.html
>
>The wikipedia page tell some of the problems with A weighting,
>though not so much for solutions.
>
>I was just wondering, if you take two similar but different audio
>signals and switch between them at, say, 1kHz, how the sound
>changes with relative amplitude. Assuming no definite phase
>relationship between the two.

None of these weighting schemes capture much of the perceptual element.
That factor which makes us want to turn up the radio when a great piece of
music comes on, because it sounds so much quieter than the Barry Manilow
song which preceded it. Your 1kHz chopped signals will probably sound
horrible, and are therefore likely to be perceived as loud.

Steve

From: glen herrmannsfeldt on 28 May 2010 00:03
steveu <steveu(a)n_o_s_p_a_m.coppice.org> wrote:
(snip, I wrote)

>>I was just wondering, if you take two similar but different audio
>>signals and switch between them at, say, 1kHz, how the sound
>>changes with relative amplitude. Assuming no definite phase
>>relationship between the two.

> None of these weighting schemes capture much of the perceptual element.
> That factor which makes us want to turn up the radio when a great piece of
> music comes on, because it sounds so much quieter than the Barry Manilow
> song which preceded it. Your 1kHz chopped signals will probably sound
> horrible, and are therefore likely to be perceived as loud.

The idea, though I don't know that it actually works, was that
as the amplitudes got closer the amplitude of the chopped signal
would get smaller. Even more, but less obvious, than it
would follow the appropriate weighting.

-- glen
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