Acoustic Phonetics

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Acoustic Phonetics

• MBROLA
• Waveforms
• F0/Pitch
• Spectra
• Time domain measurements analysis
• Frequency domain measurements analysis
• Male vs female speech

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MBREdit Example .pho file
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Sounds and Speech

• Words contain sequences of sounds
• Each sound (phone) is produced by sending signals
  from the brain to the vocal articulators
• The vocal articulators produce variations in air
  pressure
• These variations are transmitted through the air
  as complex waves
• These waves are received by the ear and signals
  are sent to the brain

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Praat Speech Analysis Tool Waveform,
Spectrogram, Pitch, Formants
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Synthetic vs. Natural
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Waveforms

• Plot of change in air pressure with time
• Amplitude
• Compression/Rarefaction
• Speech intensity/loudness
• Frequency
• Cycles per second (Hz)
• Speed
• Metres per second (ms-1)
• Wavelength
• Metres (m) / Microns / Angstroms (Å)
• Related by

Wont concern us for now
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Fundamental Frequency
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Fundamental Frequency

• F0 (pron. F-zero)
• Rate of opening/closing of glottis
• Vocal folds do not vibrate like strings but F0 is
  dependent on similar factors
• Perceptual correlate is pitch
• Do not confuse with formant frequencies F1,
  F2,!!!

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Constant VT configuration varying pitch
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Spectra

• Think of a graphic equalizer
• Speech made from waves of many frequencies
• Spectrum plots (log) power against frequency
• Peaks related to resonant frequencies in VT
• Formants
• Centre frequency
• Bandwidth
• Spectral slice
• Spectrogram
• Overhead view of slices against time
• Darkness related to power

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Vowels vs Fricatives
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Spectrum /u/
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Spectrum /i/
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Spectrum S
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Constant pitch varying vocal tract configuration
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Time-domain Analysis
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Male speech
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Female speech
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Spectral Tilt

• Refers to general slope of spectrum
• Higher formants are weaker than lower formants
• Phonation is most significant factor
• Greater spectral tilt in female speech
• Ratio of lower formant amplitude to higher
  formant amplitude greater in males