A stereo sound circuit device for providing three-dimensional surrounding effect
has a difference circuit for acquiring difference signal of a left channel sound
and a right channel sound. The stereo sound circuit device further provides a filter
circuit consisting of a first and a second filtering operation units for applying
a first and second filtering functions to the difference signal output from the
difference circuit for generating a three-dimensional surrounding sound signal.
The first filtering function implements a band pass filter with a central frequency
of about 7.23 KHz. The second filtering function implements a band pass filter
with a central frequency of about 318 Hz. A signal level adjust circuit is provided
for adjusting the signal level of the sound signal output from the filter circuit.
A mixer is provided for combining the adjusted three-dimensional surrounding sound
with the original left channel sound and right channel sound.