Dan Dugan wrote:
> I monitor my nature recordings with an analyzer, and I've noticed a
> quite visible (though not audible to my ears) high frequency cut-off
> around 16K. It seems to slide up at lower levels and down a little at
> higher levels, though it only moves over 1/3 octave or so.
>
> I had expected that this low-pass effect would have been sufficient
> for my sharp-eared intern to pick up in the blind comparison, but it
> didn't happen.
I bet you will find that your intern, as with most, if not all adults,
does not have good enough hearing to make the discrimination at those
frequencies. It's not hard for the hearing at those frequencies to be
down enough that the entire low level area simply drops out of the
bottom of the ability to hear. At best it's the sort of thing that would
require that there be little or no sound from lower frequencies to mask it.
When I was doing hearing tests for the army in the 70's probably 3/4 of
the draftees had high frequency hearing loss of some amount. And we only
tested up to 8kHz. It was very rare to see someone who had the same
levels all the way that high. Typical for those with good hearing was
10-20dB down at 8kHz. And a lot were almost gone at 8kHz.
Me, I'm down 50dB at 16kHz. A down side of getting older.
> Does anybody know what version ATRAC is in the Sharp MD-MT90? I play
> back on a Sony MDS-JE520.
Sharp does not use Sony ATRAC chips, but has their own set with
different version designators and somewhat different characteristics.
I'm not sure on that one, but it dates from when 4.5 was just getting
into Sony portables and Sharp is usually slightly behind as they tend to
play me too, and probably copy a lot from the Sony chips. The 16k
divider is characteristic of ATRAC 4 for Sonys. By 4.5 it's moved a fair
amount higher and is not so obvious. More like maybe 18kHz. Your Sony
deck is ATRAC 4.5.
That frequency is one of the major break points in the way ATRAC breaks
up the sound signal for analysis. Most of the recent changes in ATRAC
have occurred above that line as they have managed to preserve more and
more of the original up there. Real tricky since samples are scarce at
that level with 44k sampling rates.
Walt
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