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Question re Just Noticeable Difference in Perceived Loudness

Noral D. Stewart noral at ix.netcom.com
Tue Aug 3 12:16:12 EST 1999

Bill Bolton wrote:
> To conclude a discussion in another news group, I am looking for
> primary citable sources on exactly what is the minimum increase in
> sound pressure level to produce a "just noticeable" difference in
> loudness across a statistically significant sample of the general
> population.
> I have found conflicting claims, from seemingly authoritative sources,
> for values from 1dB to ~2.5dB.  However, none of them points to
> citable experimental proofs, and all seem to rely on a "common
> knowledge" or a "it has been shown" basis for their statements.
> As an broadcasting engineer, I had been taught that the value for
> reliable "just noticeably louder" discernment for any large group of
> people was around the 2 to 3dB mark, but I cannot locate a proof for
> any value?!?
> Any assistance would be greatly appreciated.
> Thanks,
> Bill
> Bill Bolton
> Sydney, Australia

There was a discussion about this in another newsgoup a while back.  I
do not have citations at hand.  However, the important point is that you
have to be careful about the circumstances of the comparison.  Many of
the experiments are based on listening to sound suddenly changed in
level.  In that case people can hear changes of much less than 2 or 3
dB.  However, if you leave some dead time between the samples or vary
the level slowly, it takes about 3 dB to be just noticeable or 5 or 6 dB
to be clearly noticeable.

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