AES $BEl5~%3%s%Y%s%7%g%s(B 2009
Poster Session P3
P3 — $B;0
Saturday, July 25, 12:00 — 16:00 (Core Time for Odd Numbers:
14:00-15:00, Core Time for Even Numbers: 15:00-16:00)
$B:BD9(B: $B4dC+(B $B9,M:(B ($BElKLBg3X(B)
P3 - 1 $B2>A[4D6-$N$?$a$N%^%k%A%A%c%M%k2;6A9g@.K!$K4X$9$k8!F$(B
A method on multi-channel sound synthesis is proposed for creating virtual acoustic environment in computer graphics productions. Impulse responses with spatial information are generated from virtual sound source distribution. For desired reproduction channel setups, total impulse response is decomposed into channel components, and each response is convolved with source signal. The method is easily adaptable when location and direction of observation point in virtual graphical scene switches frequently.
P3 - 2 $BH?6A$r4^$s$@(BHRTF$B$K$h$k#3(BD$B2;6A%7%9%F%`9=C[(B
In this paper, we proposed a new method using HRTFs that contain room reverberations(R-HRTF). The reverberation is not added to the dry sound source separated with HRTF but contained at their measured process in the HRTFs. We measured the HRTFs in a real reverberant environment for directions of azimuth 45, 90, 135 (left side) and elevation from 0 to 90 (step of 10 degrees) degrees then constructed a 3D sound system with the measured R-HRTF with headphones, examine if the sound reality is improved.
As a result, we succeed to create 3D spatial sound system with more reality compared with traditional HRTFs sound system.
P3 - 3 3$B
Artificial reverberation is often used to increase reality and prevent the in-the-head localization in a headphone based 3-D sound system. In traditional method, monaural reverberations were used. In this research, we measured impulse responses of an ordinary room by Four Point Microphone method, and calculated the sound intensity vectors by the Sound Intensity method. From the sound intensity vectors, we obtained the image sound sources. A binaural reverberation was reconstructed by the estimated image sound sources. Comparison experiments were conducted for 3 kinds of reverberations, i.e., monaural reverberation, binaural reverberation and binaural reverberation added with Head-Related Transfer Function. From the results, we could clarify the 3-D sounds reconstructed by binaural reverberation with head-related transfer function has the best spatiality.
P3 - 4 $BDc<~GH?tBS0h$K$*$1$kN><*4VAj4X78?t$NJ[JLD4::$H%@%_!<%X%C%I%^%$%/$rMQ$$$?l7WB,%$%s%Q%k%91~Ez$K$h$k8!>Z(B
We investigated the discrimination of sounds that have interaural correlation coefficient (ICC) of low frequency sound below around 100 Hz by using 1/4 octave band noise in dichotic listening. We also measured ICCs at low frequencies in several rooms with different volumes. The ICCs were obtained from an impulse response recorded by a head and torso simulator. At reference ICC 1.0 the lower threshold is 0.98; at 0.9 it is 0.85, and the upper threshold is 0.96; and at 0.8 the lower one is 0.68, and the upper is 0.88. The equivalent subjective diffuseness for the 1/4 octave band noise with the center frequency of 106 Hz and ICC of 0.9, are obtained by ICC of 0.71 at 250 Hz and ICC of 0.34 at 500 Hz. The measured ICC in a small room with a volume of less than 100 m3 is almost 1, and the ICC in large room with a volume of more than 1700 m3 is about 0.8.
P3 - 5 $B<*$N5UB&$K$*$1$k4JN,2=$5$l$?(BHRTF$B$rMQ$$$?2;A|Dj0LG=NO$N2A(B
Simplification of head-related transfer functions (HRTFs) is important for effective implementation of their synthesis from computational point of view. It can be found from the frequency resolution of the auditory system that the detailed spectral form of the HRTFs is not evaluated at high frequency region. This may enable the simplification of the HRTFs to some extent. In this paper, the HRTF on the contralateral side was flattened in the higher frequency region than a certain frequency so as to retain the interaural level difference and interaural time difference. To evaluate the influence of simplified HRTFs, a localization test was carried out. The experimental results showed that HRTFs on the contralateral side could be simplified above 4 kHz.
P3 - 6 $B8eJ}2;8;$NF,ItEAC#4X?t$K$*$1$kDc0h$N<~GH?tFC@->e$NC+$N6u4VJ,I[(B
Previously it was reported that the lowest-frequency spectral notch (first notch) on head-related transfer function (HRTF) play a role in sound image localization; high-frequency spectral notches (called N1 and N2) are important for sound image localization in elevation. However, another spectral notch (labeled N0) at relatively lower frequency appear in the same frequency range for sound sources behind a listener. In this study, we examined the spatial distribution of such low-frequency notches based on several subjects' measured HRTFs, and subsequently investigated whether such spectral notches can contribute to sound localization. The results showed that, in some cases, N0 exists at lower frequency than N1, indicating that a N0 provides localization cues for sound sources behind a listener.
P3 - 7 $BMq7?%9%T!<%+%7%9%F%`(B