speech final pt 1

• what is the difference between a vowel and a consonant?

  vowels are produced by relatively free passage of the airstream through the larynx and oral cavity and consonants are produced with one or more areas of constriction, making them voiced or unvoiced
• who do we credit the understanding of the vocal tract to?

  gunnar fant, kenneth stevens and arthur house
• acoustic theory of speech production


  published by fant, states two fundamental characteristics of speech sound production

  - features of the vocal tract can be inferred from its acoustic output

  - speech production may be broken down into two major components (source filter)
• source


  vocal folds
• filter


  resonator of sound, everything the sound goes through, the vocal tract
• resonator


  an object (head and neck) or medium (air) that is set in to motion
• How does the vocal tract act as a filter?


  it resonates the source signal by allowing certain frequencies to pass through the filter with greater amplitude than other frequencies
• formants


  the characteristic resonances of the vocal tract, bands of acoustic energy in a spectrogram

  - located at the same frequencies whether you provide energy or not
• F1


  - formant inversely related to tongue height

  - Influenced by oral cavity opening and constriction of lower larynx

  - higher tongue height, lower it is
• F2


  formant directly related to how anterior or posterior the tongue is in the mouth

  - influenced by the shape of the posterior portion of the tongue

  - more anterior, higher it is

  - more posterior, lower it is
• F0 and harmonics


  Determined by the rate of VF vibration
• what determines harmonic filtering?


  depends on the resonant characteristics of the vocal tract, which also determines the vowel that is produced
• output spectrum


  source spectrum being put through the filter function
• what specifies the frequency of a given formant?


  length and cross section of the vocal tract, closed end is VF, open end is lips and mouth
• how to calculate formant frequencies


  4 multiplied by tube length = x

  34,000 ÷ x = F1

  
  

  F1 x 3 = F2, F1 x 5 = F3
• spectrogram for vowels

  
• vocal tract & formants frequencies

  inverse relationship
• harmonics


  multiples of the f0, Describing sound source
• wideband spectrogram


  see formant characteristics better
• narrow band spectrogram


  better for visualizing harmonics
• why does the vocal tract resonate best at a frequency 4x the length of the tube?


  the longest possible wavelength provides a velocity maximum at the opening of the tube is 1/4th of the tube
• node


  volume velocity minimum
• antinode


  volume velocity maximum
• source effect on vocal tract


  does not change its characteristics
• vocal tract effect on production


  - does not add energy

  - selectively allows a greater or lesser amount of energy of each harmonic to be radiated out of the vocal tract
• how can you predict the acoustic output of all vowels?


  - knowing the location and degree of constriction within the vocal tract
• what constricts the vocal tract?


  tongue, jaw, and lip movement
• how does length and cross sectional area of a tube relate to the vocal tract?


  length is length and constrictions alter cross sectional area

  - ex. r distortion and speech errors
• two main rules for formant frequencies


  - a constriction at/near an antinode will lower the formant frequency

  - a constriction at/near a node will raise the formant frequency
• F3


  not as easily related to changes like other formants, may be influenced by lip rounding and/or tongue tip
• vowel quadrilateral


  representation of a vocal tract posture during vowel production

  - horizontal axis is tongue advancement

  - vertical axis is the tongue height

  - not a perfect depiction of vocal tract configuration
• four main corner vowels

  /i/high front, /u/high back, /a/low front, /ɑ/ low back
• forward vowels


  increase separation between f1&f2
• back vowels


  f1 & f2 are closer together
• Vowel Formant Normative Data


  natural resonant frequencies of vocal tract vary depending on the vocal tract posture

  - cannot specify absolute values

  - range of frequencies in which the relationships between formants are defined
• rhotacized vowels


  lower the f3, suspected to be a result of changes in the tongue blade and or tongue tip

  - sides of tongue curl up against molars

  - tongue tip may curl backwards
• monophthongs


  pure vowels produced with a consistent vocal tract posture
• diphthongs


  sound formed by producing two consecutive vowels in a single syllable with an uninterrupted transition from the first vowel to the second vowel & always ends in a high vowel, greater change in F2
• acoustic filter


  selectively passes certain frequency components of a complex wave, some frequencies are passed more effectively than others
• 3 main types of filters

  low pass filter, high pass filter, band pass filter