This is an interesting turn to the conversation, and I just wish this wasn't my busiest time of year.
Eric, what you propose is interesting - and I've always ben interested in differences in cognitive processing of reverberant material - or, more largely, indirect sound - that which is (naturally) caused by 'sources' but does not directly emanate from those sources. It is known that there are various deficits in Auditory Scene Analysis associated with a range of developmental cognitive 'disorders' - in Schizophrenia (I've a reference somewhere after corresponding with a medical researcher in Sweden), in autism spectrum disorders, dyslexia, bipolar disorder, some dementias and probably others. Your thesis that there may be significant differences in individuals' capacities to cognitively cleave 'source content' from reflected sound seems jolly plausible. On the one hand, we have blind-from-an-early-age folk such as Daniel Kish, who could echolocate to a remarkable extent, on the other hand, we have many (of us!) with some age-related deficits that make it much harder to sort out 'cluttered' scenes. Hearing aids are very little help in the latter, and often may impede performance. It also makes little sense that we try to measure 'intelligibility' of spaces without a decent reckoning of the spatial character of reverb - it's often measured as a mono (or rather, non-spatial) effect. Yet we know that performance in echo suppression is superior in the binaural case over the monaural case. Therefore, there is something in the spatial nature of reverberation that can be of utility in normal hearing that can help de-conflate (I made that up) the physically conflated direct and indirect signals. Finally, although binaural technologies could be used to explore much of what you want to investigate, it has to be said that the control of perceptible range and depth of field in synthesised soundfields ( even with personalised HRTFs) is still not quite adequate. It seems to me, though, that you could get fairly usable soundfields by constructing higher-order ambisonic fields using synthetic means - recording individual components and assembling the field. This way, you could even, by slicing it right, have some experimental control of relative levels of sources and 3-d ambience. In fact, I've a notion that what you're doing could be used, not only for testing purposes, but actually for training purposes - you could make an environment where people could be taught to improve their performance in reverberant environments - that would be quite exciting. Good luck with the project, and do feel free to ask for help! regards ppl Dr. Peter Lennox School of Technology, Faculty of Arts, Design and Technology University of Derby, UK e: [email protected] t: 01332 593155 ________________________________________ From: [email protected] [[email protected]] On Behalf Of Eric Carmichel [[email protected]] Sent: 06 June 2012 19:37 To: [email protected] Subject: [Sursound] Red is blue & sideways is straight ahead Hello All, First, many thanks for taking time to read this. This may be one of my better attempts at communicating what I’m attempting to do. I very much appreciate and respect all the input regarding human perception (re prior posts / the sound of vision). Professor Robert Greene wrote *...But right now, no one can know what anyone else experiences except in some structural sense.* I fully agree, but we (experimenters, psychologists) would have to provide the same physical stimulus for participants to agree on what *red” is. This means that light reflecting off of the *red* object contains the electromagnetic wavelengths requisite for stimulating the retinal cones (and rods too?) and eliciting a perception of the colour red (or the light itself is could be *red* by physical definition). Same goes for audio stimuli. I believe it would be interesting to study how the hearing impaired *hear* reverberation. Have you listened to the Scottish prayer example that is often used in classroom demonstrations? This so-called “ghoulies and ghosties” demonstration (found on the “Harvard tapes”) has become somewhat of a classic. The recording is of a hammer striking a brick followed by an old Scottish prayer. The reader is Dr. Stanford Fidell. Playing the recording backwards focuses our attention on the echoes. Practically no one reports hearing echoes in small (although reverberant) spaces when a transient sound is initiated. The echoes are not *heard* although the reflected sound may arrive as much as 30 to 50 ms later. The Scottish prayer demonstration is designed to make the point that these echoes do exist and are appreciable in size. Our hearing mechanism somehow manages to suppress the late-arriving reflections, and they go unnoticed (at least for the majority of us). There is reason to believe that hearing-impaired persons have greater difficulty suppressing reverberation (a central processing issue, not necessarily peripheral organ dysfunction??). Hearing and consciously perceiving these echoes could, then, impart a deleterious effect on word recognition ability. But without providing the same physical stimulus to the hearing impaired listener, can we determine the magnitude of effect? If the recording of the hammer (transient) is perceived as being the same regardless whether it is played in reverse or not, we can make inferences regarding echo suppression. But if the recording used for one population (normal-hearing listeners) is not identical to the recording used to study a different population (e.g. hearing-impaired listeners), what initial inferences can we make about the latter’s perception under reverberant conditions? A recording / playback system that includes echoes coming from multiple directions could provide additional insight (and real-world validity). All I’ve been saying is that the one variable that can be controlled is the physical stimulus. Stimuli that represent real-world scenarios have more external validity than tightly controlled sounds made up of monaural buzzes, clicks or tones. Similarly, it’s relatively easy to build and program a robot that can navigate in a virtual world built around well-defined colors, blocks and shapes; understanding how we navigate in the real (complex) world requires more complex stimuli (e.g. Rodney Brooks’ robots successfully navigate over difficult terrain without a priori info about the environment). We will never know what these robots are *thinking* (some don’t even run on code), but we can still measure their performance and then find ways to improve on the design. I wish to improve hearing aid and cochlear implant design; consequently, I need physical stimuli that represent the world outside of the laboratory. This has been my impetus for exploring Ambisonics. Naturally, I'm greatly enjoying the musical / artistic aspects of Ambisonics as well. Kind regards, Eric -------------- next part -------------- An HTML attachment was scrubbed... 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