Formant Regions Research Articles

Realization of Prosodic Features in Whispered Speech

Experiments utilizing a visible-speech analyzer showed that changes of pitch in normal (voiced) speech are replaced in whispered speech by shifts of some formant regions accompanied by added noise between the higher formants.

Realization of Prosodic Features in Whispered Speech

Several investigators have dealt with the problem of whispering in tone languages. As the perception of pitch changes demands a certain degree of periodicity (voice) within the speech sounds, it was difficult to see how tonal features could be preserved in whispered speech. Observations with Chinese speaking people, however, had indicated that there is no remarkable loss of intelligibility if Chinese is whispered instead of being spoken normally. The same result was found in Indo-European languages where no tones are used as phonemically distinctive elements. Intonation here belongs to the suprasegmental (prosodic) features, different types of intonation being correlated with different speech situations. Experiments were carried out by using a visible-speech analyzer which demonstrate that changes of pitch in normal (voiced) speech are replaced by shifts of some formant regions in whispered speech, sometimes accompanied by considerable broadening of the formant regions due to an increased velocity of the air stream passing the glottal fissure.

Some Results of the Analysis of Singing Voice

Oscillographic records of some masculine voices were made by means of high quality electroacoustic devices. Vowels u(oo), o, a (ah), e, i (ee) of various pitch from 94 cps to 490 cps were recorded. The records lasting 0.1 sec were made at the moment of the stationary, prolonged sounding of the vowel. The harmonic analysis of different periods of the voice of an artistic singer showed a sharply defined increase of harmonic components in two narrow bands of the spectrum: about 400–600 cps and about 2200–2800 cps. Doubtless in well-trained, good voices there are characteristic “singing formants,” practically the same for all vowels. For the vowels “u” (oo) and “i” (ee), the lower formant sometimes gets as low as 250–300 cps. The higher formant is characteristic for a “metallic” timbre of voice. In the voice of an inexperienced singer (baritone) with a strong but sharp timbre of voice and noticeable fall of loudness higher than mi♭ (325 cps), these sharply defined singing formants are not observed; the whole region of harmonies higher than 1500 cps shows a general increase. It is suggested that the singer arranges formant regions characteristic of a vowel and necessary for good articulation only in the beginning of a vowel (in the period of attach) after which he quickly rearranges the vocal apparatus to the singing position, which is almost the same for all the vowels. The quick and distinct rearrangement to the singing position is a necessary quality of a trained voice. The above-mentioned results agree with our former investigations of 1927 and with the investigations of Bartholomew who found a high singing formant in the region about 2800–3200 cps.

A Formant Tracker for Speech Sounds

The central frequencies of the principal resonance regions, or formants, have been found to contain sufficient information to resynthesize intelligible speech, as far as vowels and other nonturbulent sounds are concerned. When a single formant is isolated by filtering, one-half the average zero-crossing density, ρ0, is shown to be a convenient approximation to the formant's central frequency. Filters which are controlled electronically by a preliminary approximation to the first-formant frequency, in such a way as to isolate the first two formant regions, have been built and tested. LP and HP filters for the first and second formants, respectively, are based on a circuit by Linvill which uses a transistor negative-impedance converter. An alternate filter of the tuned-circuit type has proved more satisfactory for the first formant. The variable elements in the HP and tuned-circuit filters are Increductors, while the LP filter uses a circuit based on the Miller effect to represent an electronically controllable capacitor. [The research in this paper has been made possible through support and sponsorship extended by the Electronics Research Directorate of the Air Force Cambridge Research Center, under Contract No. AF19(604)-1039, Item I.]

A Study of the Vowel Formants of Well-Known Male Operatic Singers

The formant regions of vowels sustained by well-known male operatic singers were compared with each other and with those of untrained voices. Since vowel samples from commercial phonograph records were too short for electrical harmonic analysis, these samples were re-recorded on circular grooves. Analysis consisted of measuring the energy content of the individual harmonic partial tones. The result of this method seemed to be more informative in many ways than those obtained by using the sound spectrograph which shows only the general formant regions. Three important formants were found in the male voice, although the third of these was more prominent in trained voices. A fourth of minor importance occurred in trained voices only. The frequency positions of the three important formants are found to be in dose agreement for the various voices analyzed.