69dodge
19th August 2005, 03:14 PM
Hey jj, what do you think about this?
It was double blind.
from http://jn.physiology.org/cgi/content/full/83/6/3548
The fact that we used an entire piece of natural music lasting 200 s as sound stimuli instead of short fragments of sounds might explain the discrepancy between our findings and those of previous studies carried out around 1980 to determine the format for digital audio CDs (e.g., Muraoka et al. 1978; Plenge et al. 1979), which concluded that the presence of sounds containing a frequency range above 15 kHz was not recognized as making a difference in sound quality. The CCIR (1978), and the current International Telecommunication Union-Radio communication sector (ITU-R 1997), have recommended that sound samples used for the comparison of sound quality should not last longer than 15-20 s (CCIR 1978; ITU-R 1997), and that intervals between sound samples should be about 0.5-1 s (CCIR 1978) because of short-term human memory limitations. Most of the previous psychological experiments, including the studies by Muraoka et al. (1978) and Plenge et al. (1979), were carried out using, essentially, the sound presentation method recommended by the CCIR. We also examined the psychological evaluation using the same material and sound presentation system as was used for the present study, but followed the presentation method recommended by the CCIR, and confirmed that the results were in agreement with the studies by Muraoka et al. (1978) and Plenge et al. (1979).
In our EEG and PET experiments, we focused on physiological brain responses and objectively evaluated the effect of the combination of audible sounds and inaudible HFCs [high frequency components] on brain activity, independent of a subjective evaluation of sound quality. According to the EEG measurements, the occipital alpha-EEG gradually increased over several tens of seconds after the exposure to FRS [full range sound] began, and this increase persisted for several tens of seconds after FRS ended. These findings suggest that the phenomenon that we call the hypersonic effect may involve some neuronal mechanisms that can be characterized by delay and persistence for as long as several tens of seconds. It seems, therefore, that an exposure to FRS shorter than 20 s, as recommended by the CCIR and ITU-R, may be insufficient to introduce a physiological effect. By the same token, a short exposure to HCS [high cut sound, i.e., sound from which inaudibly high frequencies were filtered out] following FRS with a short interval of 0.5-1 s may not be enough to withdraw physiological effects, if any, induced by the preceding FRS. Based on this physiological consideration, we performed our psychological experiment with sound materials of longer duration. The results showed a significant difference between FRS and HCS in some elements of sound quality. That difference was evident despite the fact that a long presentation time should make it more difficult to detect subtle differences between two materials due to the limitation of short-term auditory memory. Our findings suggest the possibility that the results of the previous psychological studies may not be valid in a situation where humans are continuously exposed to auditory stimuli such as music or environmental sounds.
It was double blind.
from http://jn.physiology.org/cgi/content/full/83/6/3548
The fact that we used an entire piece of natural music lasting 200 s as sound stimuli instead of short fragments of sounds might explain the discrepancy between our findings and those of previous studies carried out around 1980 to determine the format for digital audio CDs (e.g., Muraoka et al. 1978; Plenge et al. 1979), which concluded that the presence of sounds containing a frequency range above 15 kHz was not recognized as making a difference in sound quality. The CCIR (1978), and the current International Telecommunication Union-Radio communication sector (ITU-R 1997), have recommended that sound samples used for the comparison of sound quality should not last longer than 15-20 s (CCIR 1978; ITU-R 1997), and that intervals between sound samples should be about 0.5-1 s (CCIR 1978) because of short-term human memory limitations. Most of the previous psychological experiments, including the studies by Muraoka et al. (1978) and Plenge et al. (1979), were carried out using, essentially, the sound presentation method recommended by the CCIR. We also examined the psychological evaluation using the same material and sound presentation system as was used for the present study, but followed the presentation method recommended by the CCIR, and confirmed that the results were in agreement with the studies by Muraoka et al. (1978) and Plenge et al. (1979).
In our EEG and PET experiments, we focused on physiological brain responses and objectively evaluated the effect of the combination of audible sounds and inaudible HFCs [high frequency components] on brain activity, independent of a subjective evaluation of sound quality. According to the EEG measurements, the occipital alpha-EEG gradually increased over several tens of seconds after the exposure to FRS [full range sound] began, and this increase persisted for several tens of seconds after FRS ended. These findings suggest that the phenomenon that we call the hypersonic effect may involve some neuronal mechanisms that can be characterized by delay and persistence for as long as several tens of seconds. It seems, therefore, that an exposure to FRS shorter than 20 s, as recommended by the CCIR and ITU-R, may be insufficient to introduce a physiological effect. By the same token, a short exposure to HCS [high cut sound, i.e., sound from which inaudibly high frequencies were filtered out] following FRS with a short interval of 0.5-1 s may not be enough to withdraw physiological effects, if any, induced by the preceding FRS. Based on this physiological consideration, we performed our psychological experiment with sound materials of longer duration. The results showed a significant difference between FRS and HCS in some elements of sound quality. That difference was evident despite the fact that a long presentation time should make it more difficult to detect subtle differences between two materials due to the limitation of short-term auditory memory. Our findings suggest the possibility that the results of the previous psychological studies may not be valid in a situation where humans are continuously exposed to auditory stimuli such as music or environmental sounds.