SACD vs. CD test synopsis

[Feanor]

In case anyone missed the original (as did I), I'm passing on this MIXonline synopsis of the Amerian Engineering Society's journal article, Audibility of a CD-Standard A/D/A Loop Inserted Into High-Resolution Audio Playback. (My thanks to Duilawyer at AA.)

Apparently the test was a rigorous, ABX DBT. An interesting aspect is the comparision was between stereo SACD layers and the same layer down-sampled to 16/44.1, (not an SACD layer to CD layer comparison as you or I might do).

Read on for the conclusions. As with any DBT, the results can't prove that differences don't exist, only that they couldn't be detected by the actual participants under the conditions of the test. Basically correct identification of SACD vs. CD was equivalent to coin tosses.

After the synopsis itself the authors proceed to talk about a few things including why hi-rez might sound better for spacial clues and how the "comb effect" might created perceived differences because of listener postion that aren't really attributable to the equipment or sources.

As to the spacial clues, it is quoted that humans can detect 5 microsecond difference in sound reaching the right as opposed to left ear. 5 microseconds is not within the 16/44.1 resolution. Of course this would pertain to left vs. right source channel, not left vs. right speaker. And obviously it would explain why difference were heard and not why they weren't heard.

The authors mentioned the "comb effect" which is frequency resonse variations on account of differences in listening position (in non-anechoic rooms such as the test rooms used). This is offered as an explanation why changes are heard, say, when the listener gets up to swap cables and doesn't return to exactly the same listening position. So in the case of these particular tests (non-)differences weren't heard because the listeners didn't have to get up to swap anything, they only had to press a button.

What wasn't discussed at any length is the placebo effect, viz. perceived differences are created by the listeners expectations rather than by actual differences.