Hello Guilherme, I have some insight regarding your question re KEMAR and the Neumann acoustical test fixtures/heads. Briefly, KEMAR was designed with hearing science in mind. The torso was designed to approximate "average" human size (I think we have, on average, grown since the introduction of KEMAR). Additionally, the material from which KEMAR is fabricated has an absorption coefficient to match that of humans (clothed or not clothed??--will have to refer to Knowles Electronics for this info). KEMAR is generally equipped with two interchangeable ear sizes: Large and small. If you look at impulse responses obtained with a KEMAR (e.g., the widely used IRs that came from a MIT lab study by Gardner et al), you'll probably see in the info section which of the two ears was used. Internal to KEMAR, their are microphone clamps for 1/4- or 1/2-inch mics (two different clamps for each mic size). A pig-tail adapter allows two Bruel & Kjaer mics (L + R) to fit within KEMAR's limited head space (getting into the mind of KEMAR is a tight fit?). When making a recording using internal mics (not the same as mics proximal to the ears conchas), the resonant peak created by KEMAR's ear canals will have to be considered. The recordings with peaks work well with deep-seated earphones, such as EAR phones, that otherwise destroy the ear's natural canal resonance. Note: Earphones worn OVER the ears modify the natural resonance, but don't destroy it. One could argue that the (approximate) 6cc volume of circumaural headphones over the ears' 2cc volume will certainly change things a bit. However, the active drivers of headphones may result in a larger "equivalent" earcup volume that imposes less of a change than one might predict. (Analogy here: The B&K acoustical calibrator has a large equivalent volume despite a small physical volume--this large virtual volume minimizes error caused by mic placement in the calibrator.) Just be aware that mic placement, either in KEMAR or proximal to concha, will affect recordings at the very important mid frequencies. Another thing about KEMAR is that it is designed to accomodate a Zwislocki coupler. Maybe it's more accurate to state that the Zwislocki couple was designed to fit inside of KEMAR. Anyway, the Zwislocki coupler mimics middle ear function. Briefly, it is mathematically equivalent in compliance, mass, etc. of the middle ear (tympanic membrane, ossicles, ligaments, etc.). If you wish to learn more about KEMAR recordings, I recommend a search for articles authored by Zwislocki, Mead Killion (of Etymotic Research), and others. One article by Killion is titled "Zwislocki was Right." A Google search for Jozef Zwislocki will reveal some very interesting information regarding human hearing.
Now for the Neumann head: I believe this was designed primarily for high-fidelity, binaural recordings. I have listened to recordings made with the Neumann head (and IRs obtained via the Neumann head), but can't state whether these are significantly different from KEMAR recordings. Like many things, one has to consider the overall system: Recording and playback. I've heard KEMAR recordings that suck, and others that were fabulous. Why the difference between recordings? Not sure, as I didn't have all the details. Maybe getting recordings from the same venue and source would help, but I don't know of any direct A-B material for comparison. I hope this info helps some. As usual, I'm writing off the cuff without any reference material, so please pardon any inaccuracies. At least the people mentioned above (Killion, Zwislocki) will reveal accurate and detailed info. Best regards, Eric C. -------------- next part -------------- An HTML attachment was scrubbed... URL: <https://mail.music.vt.edu/mailman/private/sursound/attachments/20130329/6136db93/attachment.html> _______________________________________________ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
