Dimensions in the Spectra of Speech Vowels
Reinier Plomp · The Journal of the Acoustical Society of America · 1966
Traditionally, the formant frequencies are regarded as the most important characteristics of the frequency spectra of vowels. It is possible, however, to approach the discrimination between vowel spectra in a more general way by considering the sound-pressure level in each of a number of passbands as a coordinate in a multidimensional Euclidean space, so that different vowels result in different points in this space. Frequency spectra of 15 Dutch vowels were determined with 18 bandpass filters and the data of 10 speakers were averaged. Computations showed that 96% of the variance of the 15 points could be explained by 4 new coordinates; these coordinates are linear combinations of the 18 original ones. By means of a rather simple apparatus, it is possible to visualize the two main dimensions by the position of the light spot of a cathode-ray tube, in such a way that the position of the spot depends upon the vowel uttered.