A simple threshold-based method is described which permits automatic d
istinction between the Spanish fricatives [theta] and [s] in the initi
al position by means of a measurement of energy and a rough determinat
ion of the spectral composition as the zero-crossing rate. All signal
analysis (including word endpoint and fricative detection) is carried
out automatically. The system was tested using a series of words conta
ining all the [theta, s]-vowel combinations possible in normal Spanish
, thus allowing for possible effects of fricative-vowel coarticulation
. To study sex-related differences, 10 men and 10 women were used as s
peakers. Both sex and fricative-vowel coarticulation affected correct
classification rate. The overall correct classification rate was 93.5%
(94% for men and 92% for women). A classification procedure using a d
iscriminant function obtained assuming Gaussian statistics achieved al
most identical results.