Untitled Quiz

Source-Filter Theory

• Source-filter theory explains speech production.
• Vocal folds act as the source, producing a sound.
• The vocal tract acts as a filter, shaping the sound into different speech sounds.

Vocal Tract Music Video

• A video demonstrates the vocal tract's movement.

Vocal Tract Input

• Details about the input to the vocal tract are provided.

Vocal Tract Images

• Images (numbered 1-10) show the dynamic movements of the vocal tract.

Source and Filter

• Periodic vocal fold vibration is the source of the signal.
• The vocal tract is the filter, which modifies the signal.

Glottal Source Signal

• Top diagram illustrates the glottal source.
• The bottom diagram shows a Fourier analysis of the source.
• The first harmonic corresponds to the fundamental frequency.
• Other harmonics are multiples of the fundamental frequency.

Glottal Source Spectrum Characteristics

• Three sources of variability in glottal source waveforms:
  • Periodic nature
  • Shape
  • Ratio of open and closed phases

Variability in the Periodic Nature of Glottal Wave Forms

• Natural vocal fold vibrations vary.
• For simplicity, normal vocal fold vibrations are considered periodic.
• Variations depend on factors like gender and age.

Average F0 by Gender and Age

• An average fundamental frequency (F0) chart is provided.
  • F0 decreases with age in both genders.

Different Vocal Signals

• Two vocal signals of the same duration are compared (upper and lower wave forms).
• The upper waveform has a period = 8 ms while the lower one has a period = 5 ms.
• The upper waveform has fewer cycles for this time period.
• The lower waveform has fewer harmonics.

Harmonics with Different Spectral Slopes

• Waveforms' return to atmospheric pressure differs in steepness.
• This difference affects the spectrum.
  • Shallower closing corresponds with greater tilt.
  • Steeper closing corresponds with shallower tilt.
• These spectral slopes represent fast or slow closure.

The Vocal Tract: A Closed Tube

• The vocal tract is approximately 15 cm long.
• Its length varies with the size of the talker (speaker).

Inputs and Responses

• The top waveform represents the glottal waveform.
• The bottom waveform represents the vocal tract response.
• Closure in vocal folds results in a vocal tract response.

Resonation in the Vocal Tract

• Vocal tract properties are excited during vocal fold closure.
• This closure excites various frequencies, often resonating within the tract.
• Once excited, sounds go through the vocal tract filter.

Source + Filter

• Vocal fold vibration is the source material.
• A filter shapes this source.
• A filter amplifies particular frequencies and truncates others.
• This leads to an output spectrum.

Formants

• Formants are peaks in the output spectrum that emphasize particular harmonics, noticeable in vowels and other consonants.
• Formants are like band-pass filters.
• There are generally three major formants.

Properties of Output

• Output is calculated using source and filter.
• Harmonics lessen with increasing frequency.
• Formants have a similar frequency amplitude.
• Filters increase the prominence of selected harmonics.