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Fig. 4.
Multiple level-of-abstraction to manage the news and traffic information
4 Experimental Evaluation
Multimedia Service applications, the Main daemon and the speech interactive agent
together are implemented and tested on X-scale 400 Mhz, WindowsCE.NET AutoPC
system. 11 Khz speech sampling rate for input and output is used for the speech in-
teractive agent. Each application program and daemon processes communicate be-
tween them using IPC method respectively according to the negotiated protocols. On
the first time, to test the application programs respectively, the speech interactive
agent and simulator are developed. After integrating works are finished, the real car
test is evaluated on integrated working environment.
For experimental evaluation of speech based user inter interface such as speech
recognition and text-to-speech, respective algorithms are evaluated respectively.
First, noise preprocessing algorithm with 2-channel microphone array is applied and
implemented for suppressing car noises. The experiments were conducted using the
CAR01 corpus from the Speech Information Technology & Industry Promotion Cen-
ter (SITEC) [23]. This corpus consists of car control and navigation related com-
mands words, isolated digit and connected four digits. As the baseline experiment
without any noise reduction method and a single channel noise reduction method
using spectral subtraction algorithm (SS) is conducted to compare the performance
improvement of the dual-channel noise reduction method.
In 2-channel noise reduction methods, we evaluated some methods using the delay-
and-sum beamformer (DS), Griffiths-Jim beamformer (GJ) [4] and eigen-decomposition
(EVD) [21]. In addition, we applied the high-pass filter (HP) to cancel the low fre-
quency component of the car environment. But the performance of the EVD method
combined with the HP and E-EVD (new two reconstructed signals) method is highly
improved. From the results as shown in Table 4 and 5, it is shown that the best per-
formance is obtained when E-EVD method is combined with HP.
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