I have shown an example, you are just unwilling to admit that it's audible
I never bothered to download those files originally because I saw the comments from others that the levels are very low and you used sine waves versus music etc. But I just downloaded all three files now, and it's clear you made a grievous error in your processing.
You say you started with the 24 bit file and reduced it to 16 bits truncated and dithered. I have no idea what you did, but the damage in both cases is
way beyond what I get when I bit-reduce the original to 16 bits. Neither of your files resembles the original sine wave, even though the recorded level is at a very reasonable -14 dB. Versus my truncated version that looks identical to the source. Here's a screen cap showing all four files in Sound Forge, with the same vertical and horizontal scaling:
So whatever you think is being proven by your files, you're mistaken. Perhaps you accidentally reduced them to all the way down to 8 bits instead of 16?
I do agree that good bass traps help with room acoustics, but they are not always that audible or measurable. It depends on the room. Likewise with dither.
The improvement in response and ringing after adding bass traps is always audible
and measurable, assuming good bass traps and an appropriate number of them. Like at least two for a bedroom size listening room.
I know of no other pro audio engineer worthy of this title that says dither and jitter are inaudible
You need to get out more.
Seriously Tom, there are a
lot of professional engineers who agree with me on this, and they are just as upset as I am to see so much time and energy wasted on non-issues like dither and jitter. In fact, you can expect to see an article about this by a respected columnist in a major magazine this spring or early summer.
--Ethan