For those who do not have access to Spatial Hearing: The Pyschophysics of Human Sound Localization, Revised Ed. By Jens Blauert, I have provided a few sentences from this book. Another book that is recommended is Binaural and Spatial Hearing in Real and Virtual Environments by Gilkey and Anderson (Chapter 13 of this book, written by D. H. Mershon, addresses distance perception). From Blauert:
“Familiarity of the experimental subject with the signal plays an important role in the localization between the distance of the sound source and that of the auditory event. For familiar signals such as human speech at its normal loudness, the distance of the auditory event corresponds quite well to that of the sound source. Discrepancies arise, however, even for unusual types of speech at their normal loudness. As an example, figure 2.7 [see note below*] shows localization in the range of distance from 0.9 to 9 m with a human speaker whispering, speaking normally, and calling out loudly (Gardner 1969).” In a subsequent chapter, Blauert writes: “The closer a person approaches a sound source in an enclosed space, the stronger the component of the primary field in comparison with that of the diffuse field (figure 3.48). The difference between the levels of the primary and reflected sound furnishes information to the auditory system about the distance of the sound source. The auditory system takes this information into consideration in forming the distance of the auditory event. This relationship has been described many times [references go back as far as von Hornbostel, 1926]...” In the next paragraph, Blauert writes: “It must be pointed out that meager statements about spatial hearing in enclosed spaces up to this point are only valid as general rules. Departures from these rules and additional effects can occur in connection with rooms of specific shapes, with particular sound sources, and with specific types of signals.” When it comes to my personal interests, I have considered distance and loudness effects as well as well as how to present them. I have created real-world stimuli that are to be presented at “normal” levels. I have included subtleties, such as talker voice level as a function of background noise level, to make the audio (and video) stimuli more realistic. For example, it shouldn’t take a lot to convince anyone that we tend to raise the level of our own voice in a noisy environment--this phenomenon is known as the Lombard effect (see, for example, Lane & Tranel, 1971). Tufts & Frank (2003) showed that talkers’ voice levels increase, on average, 5 dB for every 10 dB increase in background noise level. I am aware of studies that used restaurant noise presented at low levels (60 dBA) to maintain a favorable SNR. Conversely, some researchers used the same surround of restaurant noise (recorded with 8 Sennheiser mics) at its actual level, but elevated “normal” speech to 85 dBA to maintain a favorable SNR. What I mean by favorable is on the order of + 15 dB SNR. I should have asked, “Does the restaurant noise sound far away, or does it sound like a “quiet” pizzeria?” Research participants' thoughts on this topic might have been interesting. Anyway, I'd prefer to use a recording of a quiet environment for the instances I need a +10 dB (for example) SNR in lieu of a moderately loud restaurant simply turned down in presentation level. I also recorded "loud" speech--features of which certainly differ from whispers presented at a loud level. So how did I plan to record a variety of background noises for research? Ambisonics miking, of course! Best, Eric C. Gardner, M. B. (1969): Distance Estimation of 0 Degree or Apparent 0 Degree Oriented Speech Signals in Anechoic Space. J. Acoust. Soc. Am., pp. 47-53. *If anybody would like for me to photocopy the figure (or entire page), I will be glad to do so and upload the image to my website. -------------- next part -------------- An HTML attachment was scrubbed... URL: <https://mail.music.vt.edu/mailman/private/sursound/attachments/20130227/e42f2160/attachment.html> _______________________________________________ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
