Greetings to All, I was looking at the web link that David M. provided regarding inertial transducers, and wondered whether placing one of these devices on my living room wall would approximate the elusive infinite-baffle loudspeaker (I’m recalling articles written by the great Harry Olson). But considering that I live in a duplex and that I’m already the neighborhood’s designated mad scientist, I probably should avoid such experimentation. As far as inertial devices and the hearing sciences go (I’ll get to the topic of surround sound, too), there was a bone-conduction device that was intended to compete with cochlear implants. My understanding was that an ultrasonic carrier frequency (around 60 kHz and transmitted via bone conduction) was modulated with the speech signal. I don’t know whether the speech was presented as pulses (such as neural pulses) or as analog sound. For normal-hearing users, this would be akin wearing a conventional bone-conduction (or inertial) transducer. The ultrasonic carrier would be filtered out via inertia (as well as undetected by the inner ear), leaving only the lower-frequency speech signal to be heard. But for persons with non-functional cochleas, some other mechanism would have to be at work. I believe the company making the device was German-based and went by the name Hearing Innovations. They set up shop in Tucson, AZ (and perhaps other cities), but seemed to quickly disappear. Not sure what the story was, or whether the device worked. On to the topic of binaural listening... From a theoretical perspective, headphone listening could be quite real because real-world listening is ultimately a function of the one-dimensional pressure changes impinging on the eardrums. Recent posts suggested that headphone listening can’t provide the same stimuli or experience as real-world listening, particularly for low-frequency sounds. One very important aspect of low-frequency (acoustic) hearing is how much it can contribute to speech understanding when combined with electrical hearing (meaning implanted electrodes, or cochlear implants). I’ve written on this topic in past posts, but I will repeat that the combination of acoustic and electrical hearing results in an improvement in speech understanding that far exceeds the sum of the individual modes' individual contributions to speech scores. When it comes to cochlear implants, the question is how much benefit does this combination of modes (acoustic plus electric stimulation) provide in noisy or reverberant environments? People with cochlear implants have great difficulty hearing in noise, so improvements in this area are of great interest. I have proposed studies using a surround of noise to investigate the efficacy of EAS listening in real-world environments. To date, studies have shown improvement in speech understanding using EAS or EAS simulations (namely normal-hearing listeners donning earphones) combined with speech babble and artificially-generated reverberation (stereo or monaural). One could argue that providing natural, multi-directional reverberation (via a surround of speakers) in the sound field would be an easier listening task than listening under earphones. In a surround of uncorrelated background noise, we could use our ability to localize sounds (assuming this can be done with implantable prostheses) to segregate the speech from noisy or reverberant background sounds. But I am decidedly against the idea that the research outcomes or processing strategies optimized for headphone listening are valid for the majority of real-world listening situations, even when the headphone listening task is the more difficult of the two. Here’s an analogy. One of the few physical feats I can perform is riding a unicycle. I also used to set up obstacle courses for unicycle riding that were quite rugged. For most, riding a unicycle over rugged terrain is arguably more difficult than learning to ride a bicycle. However, I am not remotely adept at performing stunts on a bicycle despite demonstrating an ability to stay upright on a single wheel. Both activities involve balance, wheels, and pedaling, but the ability to ride a unicycle does not translate to bicycle handling skills. What I experience while listening under headphones may require more concentration than real-world listening (it depends on the task), but that doesn’t mean that my ability to concentrate on words or sentences in noise while listening under earphones has real-world application or translation. Listening under headphones with pink noise as the background noise may prove to be more difficult than listening in a surround of speakers with speech noise. But finding methods or processing strategies that improve the speech scores for a difficult task doesn’t necessarily translate to improving one’s ability to do well while attempting the conceivably simpler, real-world tasks. If I wish to study improvements in processing strategies or electric plus acoustic hearing in reverberant spaces, I need to do these using controlled but real-world listening environments. Live, learn, and enjoy life with a surround of loudspeakers. Long live Ambisonics. Best to All, Eric C. PS--I often wear headphones 2 to 4 hours a day, but not because they give me a real-world experience. Headphones do have their place and can certainly provide listening enjoyment as well as privacy. -------------- next part -------------- An HTML attachment was scrubbed... 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