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From: John O'Flaherty on 28 May 2010 09:07
On Thu, 27 May 2010 12:04:04 -0700 (PDT), snickell
<snickell(a)gmail.com> wrote:

>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?

Maybe you could conduct a pre-test with the subjects adjusting the
levels through paths A and B for equal subjective loudness (with
random order of presentation). Record the unweighted RMS levels
present after the adustment for equal loudness, and use those levels
during the test for whatever it is you are looking for in the main
test.
--
John
From: Al Clark on 28 May 2010 09:45
snickell <snickell(a)gmail.com> wrote in news:9c38ac81-c056-4f7d-94ed-
d607291d0304(a)s4g2000prh.googlegroups.com:

> 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

One thing to consider is that A-weighting is an approximation to NC (noise
control) curves at about 65dB if I remember correctly (check this value)

Hearing is actually somewhat flatter at higher levels. You can look at NC
curves to see what I mean.

If you are normalizing levels of music, I expect these levels would be at
somewhat higher SPL.

Al Clark
www.danvillesignal.com

From: Clay on 28 May 2010 10:05
On May 28, 9:45 am, Al Clark <acl...(a)danvillesignal.com> wrote:
> snickell <snick...(a)gmail.com> wrote in news:9c38ac81-c056-4f7d-94ed-
> d607291d0...(a)s4g2000prh.googlegroups.com:
>
>
>
>
>
> > 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
>
> One thing to consider is that A-weighting is an approximation to NC (noise
> control) curves at about 65dB if I remember correctly (check this value)
>
> Hearing is actually somewhat flatter at higher levels. You can look at NC
> curves to see what I mean.
>
> If you are normalizing levels of music, I expect these levels would be at
> somewhat higher SPL.
>
> Al Clarkwww.danvillesignal.com- Hide quoted text -
>
> - Show quoted text -

You can always turn it up until the ears start to bleed. This removes
the psychological effect from the measurement ;-)

Clay

From: Mark on 28 May 2010 12:07
On May 28, 10:05 am, Clay <c...(a)claysturner.com> wrote:
> On May 28, 9:45 am, Al Clark <acl...(a)danvillesignal.com> wrote:
>
>
>
>
>
> > snickell <snick...(a)gmail.com> wrote in news:9c38ac81-c056-4f7d-94ed-
> > d607291d0...(a)s4g2000prh.googlegroups.com:
>
> > > 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.
>

you can use a 1 kHz tone ( something midband of your filter) and set
the gain of your two channels ..

then apply the program material ...

if you MUST compare the loudness of program material directly (which
will be difficult to get very accurate) you should start here:

http://www.dorrough.com/

Mark
From: Randy Yates on 28 May 2010 12:17
snickell <snickell(a)gmail.com> writes:

> 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?

Hi Seth,

I would run each signal through a perceptual weighting filter and
compare the power of each output. I'm not sure where you can find
one - email me if you have trouble.

--Randy


--
Randy Yates % "And all you had to say
Digital Signal Labs % was that you were
mailto://yates(a)ieee.org % gonna stay."
http://www.digitalsignallabs.com % Getting To The Point', *Balance of Power*, ELO
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