On 26 Jul 2011, at 17:00, sursound-requ...@music.vt.edu wrote:
Date: Mon, 25 Jul 2011 20:18:42 -0400 From: Marc Lavall?e <m...@hacklava.net> After reading this difficult thread (I'm replying with a new title), I have simple questions about room sizes and speaker distances. Imagine two rooms with proper acoustic characteristics and treatments for ambisonics reproduction: the first is 3mX4m and the other is four times larger in surface (9mX12m). In both rooms there's a horizontal hexagon of speakers, and 5 speakers are against a wall. When NFC is applied in both rooms, do they sound the same in terms of distance perception when playing the same recording? Or is the same "sound object" appear to be twice as far in the largest room?
As J?rn has pointed out, the effect of the different acoustics of the rooms is hard to eliminate, and speaker placement relative to walls and other surfaces also has audible consequences. Anechoic rooms are hard to achieve, and are rather unpleasant and disturbing to be in. It is would be difficult to do an A/B comparison.
So, it is a rather hypothetical, if relevant, question. A better test would be two identical or similar outdoor rigs at different distances matched in level, with the ability to switch between them.
The "40' geese" phenomenon has been mentioned many times. John Leonard's recording, obviously fairly close perspective, when played on large systems gives the impression of very large geese. No-one seems to have an explanation for this. Possibly it is due to conflicting perceptual cues, visual as well as aural. Even without any visual aspect close sound sources seem 'bigger'. Aural perspective is not the same as visual perspective, though there are some similarities. Visual distance acuity is probably not much better than aural distance acuity. Both rely on comparison, experience and supposition.
My hunch, which I cannot back up with formal theory, is that distance perception is relative rather than absolute. So, I would expect the two 'rooms' to sound broadly similar though not identical, assuming 'proper acoustic characteristics' and appropriate NFC. Distance perception would be consistent, though different, in each 'room'.
Apart from widening the listening sweet spot, are larger rooms "better" at reproducing distance cues when using the same speaker configuration?
It has been said several times on this list that the size of the sweet spot is related to wavelength and not the size of the speaker rig, and I'm not knowledgeable enough to disagree.
Certainly larger rooms have later and lower level reflections, with lower frequency resonant nodes and a more even frequency distribution of the harmonics of those nodes. Speakers can be more easily located away from walls and corners, resulting in direct sound sound from them arriving earlier and being louder than reflected sound.
Is distance perception directly related to speaker distances?
I suspect that that it is related in the case of ambisonics, though not directly. This is more psychoacoustics than just physics or acoustics.
Ciao, Dave Hunt _______________________________________________ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
