APSIPA ASC 2011 Xi’an

A Study on Sound Image Control Methodfor Operational Support of Touch Panel Display
Shigeyoshi Amano, Takeshi Yamada, Shoji Makino, and Nobuhiko Kitawaki
Graduate School of Systems and Information Engineering, University of Tsukuba, Ibaraki, JapanINTRODUCTIONII.

PROPOSED METHOD

We examined the relationship between the volume settingof the four loudspeakers and the position localized. The
experimental conditions are briefly described in Table 1. The
subject sits down in front of the touch panel display on a desk,
without being forced to fix his/her head. This is intended to makethe system more robust against head movement.
Fig. 2 shows the average of the position localized for eachvolume setting, together with the 95% confidence interval. Asthe result, we obtained the 72 pair data of the volume setting
and the position localized.
The proposed method estimates the volume setting of thefour loudspeakers to generate a sound image on a desired
position. To do this, first the nearest eight positions to the desired
position are selected from the 72 positions obtained. The volume
setting for the desired position is then determined by theweighted sum (or the linear interpolation) of the volume settings
for the eight positions selected.
III.

EFFECTIVENESS OF THE PROPOSED METHOD

We estimated the volume setting for each of eight positions
specified. The same 10 subjects then localized the sound image
generated by using the volume setting estimated. The
experimental conditions are the same as those in Sec. II.

0Loudspeaker
438mm
Sound image

336mm

In recent years, touch panel displays have become popular inuse for personal computers. However, it has the serious problem
that touch operation is essentially difficult for sight-restrictedpeople.
One way to solve this problem is to instruct a user in theposition to be touched by generating a phantom sound image on
the position. We are now developing a system with a touch panel
display and four loudspeakers as shown in Fig. 1. In this system,sound image control plays an important role. Furuya et al.
examined the relationship between the volume setting of
loudspeakers and the position localized by subjects [1]. To
generate a sound image on a desired position, this paper proposesa sound image control method that estimates the volume settingof the four loudspeakers by using the relationship obtained
beforehand.

Vertical position (pixel)

I.

Table 1 Experimental conditions
SoundOne speech sample of a male
Distance from display to user
About 45 cm
72 settings that thoroughly cover# of volume settings
the area to be touched# of subjects
10 subjects with a blindfold mask
# of trials
5 times for each volume setting
How to answer
By touching the position localized

138
276
414
552
690

19 inch touch panel

0Fig. 1 System overview.

128 256 384 512 640 768 896 1024
Horizontal position (pixel)

Fig. 2 Localization results.

0
Vertical position (pixel)

Abstract— This paper proposes a sound image control methodthat estimates the volume setting of loudspeakers to generate asound image on a desired position. Experimental results
confirmed that the proposed method gives the appropriate
volume setting.

138
276
414
552
690
0128 256 384 512 640 768 896 1024
Horizontal position (pixel)

Fig. 3 Position specified (circle) and position localized (box).

Fig. 3 represents the position specified (circle) and theposition localized (box). We can see that the proposed methodgives the appropriate volume setting.
IV. CONCLUSIONSIn this paper, we proposed the sound image control method
and showed its effectiveness. As future work, we plan tointroduce a personal adaptation technique to improve thelocalization accuracy.
REFERENCES[1] Furuya et al., “Two-dimensional localization of a phantom sound image
controlled by the level differences among four loudspeakers in a verticalplane facing a listener,” Acoust. Sci. & Tech., Vol. 25, No. 6, pp. 493495, 2004.