S. Sakauchi et al., Subjective assessment of the desired echo return loss for subband acousticecho cancellers, IEICE T FUN, E83A(12), 2000, pp. 2633-2639
Citations number
9
Categorie Soggetti
Eletrical & Eletronics Engineeing
Journal title
IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES
We investigated the dependence of the desired echo return loss on frequency
for various hands-free telecommunication conditions by subjective assessme
nt The desired echo return loss as a function of frequency (DERLf) is all i
mportant factor in the design and performance evaluation of a subband echo
canceller, and it is a measure of what is considered all acceptable echo ca
used by electrical loss in the transmission line. The DERLf during single t
alk was obtained as attenuated band-limited echo levels that subjects did n
ot find objectionable when listening to the near-end speech and its band-li
mited echo under various hands-free telecommunication conditions. When we i
nvestigated the DERLf during double-talk, subjects also heard the speech in
the far-end room from a loudspeaker. The echo was limited to a 250-Hz band
width assuming the use of a subband echo canceller. The test results showed
that: (1) when the transmission delay was short (30 ms), the echo componen
t around 2 to 3 kHz was the most objectionable to listeners. (2) as the tra
nsmission delay rose to 300 ms, the echo component around 1 kHz became the
most objectionable; (3) when the room reverberation time was relatively lon
g (about 500 ms). the echo cumyonent around 1 kHz was the most objectionabl
e even if the transmission delay was short; and ( 1) the DERLf during doubl
e-talk was about 5 to 10dB lower than that during single-talk. Use of these
DERLf values will enable the design of mure efficient subband echo cancell
ers.