Hi Eric As always, an interesting and detailed post. I'll just comment on a couple of points...
On 3 February 2013 20:29, Eric Carmichel <e...@elcaudio.com> wrote: > Aside from masking and audiometric protocols, the idea of sound transmitted > via bone conduction is important when it comes to normal-hearing listeners. > We probably don’t give it a lot of consideration to it because the > predominant ‘sensation’ is that of hearing, so we assume that sound only > reaches the inner ear via the outer ear. What we ‘feel’ at loud concerts is > identifiable as low-frequency vibration, but this certainly adds to the > ‘sound’ (I wonder whether we could induce motion sickness if the vibration > wasn’t in time with the airborne sound). Wouldn't surprise me at all! > Scientists have a good grasp on how we hear (meaning the physiological > aspects of the peripheral auditory system), but I fear we know little on how > we ‘listen’. Isolating simple sounds allows us to study and understand > important aspects of hearing, but humans (and other critters) as well as our > environments are complex. I’ll leave discussions of man-environment > interactions to Ecological Psychologists or their opponents. Dr. Lennox - comments? > Regarding dentally-implanted hearing aids, my scant knowledge of this is that > they are bone-conduction devices. Some children (and adults) may have > stenosis or atresia that precludes them from hearing despite a normal inner > ear system. This type of hearing loss is a conductive hearing loss. By > providing sound vibration to boney surfaces (such as the mandibular process), > the inner ear receives stimulation as though the footplate of the stapes were > acting on the oval window (middle and inner ear components). Sound travels > faster in a solid medium than it does for air, so the usual directional cues > are probably lost or would take time to ‘learn’ (the other aspect of > localization). > You can take a tuning fork and, while it’s vibrating, touch it to your > forehead, teeth, or prominent (hard) area just behind your ears. It is > evident from a simple demonstration that the increase in level is not merely > a result of sound reaching the outer ear. There’s a limit to high frequency > response via bone conduction because of inertia. It takes more energy to > accelerate a large mass. The light weight of the eardrum and bones of the > middle ear (ossicles) makes the middle ear an efficient moving system over a > broad range of frequencies. The limits are set by the sensory cells (inner > and outer hair cells) of the inner ear, not the mass or compliance of the > middle ear. Some years ago ( well, actually, over two decades) we were approached by Stanton Magnetics about their Mass Inertial Transducers which are (or were, they aren't available any longer as far as I can see, though similar devices are - see http://www.maplin.co.uk/10w-vibration-speaker-671562) vibrators based on US patent us4843628. We bought a couple and played around with them, ending up particularly interested in the way you could "hear" where they were placed on your body, even if the sound was at such at a low level that you couldn't hear them via the air or feel them as a an obviously tactile sensation. > Real-world hearing is multi-dimensional. I would be curious to know whether > our sense of distance is at all affected by the feeling sensation that > reaches us (via ground vibration) before airborne waves reach us. We are > conscious of the obvious, dominant cues that affect our perception of the > world. In the absence of the dominant cues, nature finds ways to fill gaps > and make sense of our environment. Pitch and melody may not be easily > recognizable when distorted, but rhythm is often identifiable. Speech, like > music, has rhythm and intonation (prosodic features). So ‘hearing’ with our > skin seems entirely plausible, particularly if we define hearing as an active > process of making sense of vibration. Reptiles are sensitive to infrasonic > frequencies: Maybe their hearing mechanism is akin to the utricle and > saccules that are responsible for our sense of balance. In fact, the organs > of balance reside in the inner ear, so why shouldn’t they also > contribute to our perception of sound (in addition to sound-source > direction). Just some thoughts, and me rambling on another Super Bowl Sunday. and scorpions hear vibrations through their feet and have incredibly good direction sensing....I was particularly struck by your comment about distance perception, as that's one I hadn't thought about - I'll have to add that to my list All the best Dave As of 1st October 2012, I have retired from the University, so this disclaimer is redundant.... These are my own views and may or may not be shared by my employer Dave Malham Ex-Music Research Centre Department of Music The University of York Heslington York YO10 5DD UK 'Ambisonics - Component Imaging for Audio' _______________________________________________ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
