We have discovered the presence of weak sinusoidal components located at formant frequencies in voiced speech segments. We refer to them as Formant Tones. These sinusoidal components are often located close to the strongest harmonic component under the formant peak and closely t,rack the respective formant, peaks with time. The Formant Tones seem to provide crucial incremental information required to precisely identify and track the formant location. These tones are not easily discernible using standard short-time Fourier transform or linear prediction methods. However, when we decompose the speech signal into its harmonic components, tell-tale evidence of these Formant Tones is visible in their envelopes. We then remove the strong harmonic components by high-pass filtering the envelopes. The high-pass filtered envelopes are subsequently used to identify the frequency tracks of these tones. Since the Formant Tones are non-harmonic, they must originate in the vocal tract as a reaction to the impinging glottal pulses. Further, these tones appear to be angle-modulated by the glottal pulses. © 1993 IEEE