"Lord Hasenpfeffer" wrote in message

Geoff Wood wrote:

For the benefit of those not following the r.a.p thread. The (now)
famous "Absolute Threshold Of Hearing" relates to signals at
extremely low levels that are disgarded in MP3 and ATRAC coding.
Not levels like -1dB, or -10dB, or -20dB, but in the order of -60dB
and lower.

Well not really but kinda-sorta.

The usually-given threshold of hearing is the "0 dB" line on charts like
this one:

http://www.webervst.com/fm.htm

However, due to masking the just noticeable levels for reliable perception
in normal day-to-day circumstances are way far higher.

Well, thank God, somebody finally cited some hard numbers as opposed
to hard opinions regarding the Absolute Threshold of Hearing!
Sheesh!!! What was so hard about that? And what is your source for
this information? Or are you just picking them out of the blue?

For a real thrill, search google for "Fletcher Munson Curve".

-60dB in relation to what? Full Scale?

Actually, the threshold of hearing is closer to 0 dB SPL @ 1000 Hz, and 0 dB
SPL is defined in terms of physical units relevant to acoustics (pressure
over area).

Of course this value fluctuates higher and lower depending on
frequency value.

Well doooh!

It's definitely *not* a straight line even though I
drew it to look like one in my "Good_MP3_Bad_MP3.gif".

I can't believe how much bandwidth and energy has been used up with this
tiring discussion when a few minutes of research with google would provide
most of the relevant facts.