Acoustic Characteristics of Consonants

Acoustic Characteristics of Consonants

Robert A. Prosek, Ph.D.CSD 301

Robert A. Prosek, Ph.D.CSD 301

ConsonantsConsonants•Consonant articulations are more complex than

vowel articulations

•consonants are usually described in groups according to their significant acoustic and articulatory properties

•stops

•fricatives

•affricates

•nasals

•glides

•liquids

•Consonant articulations are more complex than vowel articulations

•consonants are usually described in groups according to their significant acoustic and articulatory properties

•stops

•fricatives

•affricates

•nasals

•glides

•liquids

Stop Consonants (1)Stop Consonants (1)

•Stop consonants are characterized by a complete closure somewhere in the vocal tract

•Three phases

•closure

•release

•transition

•reverse the steps for postvocalic stops

•Stop consonants are characterized by a complete closure somewhere in the vocal tract

•Three phases

•closure

•release

•transition

•reverse the steps for postvocalic stops

Stop Consonants (2)Stop Consonants (2)

•Stop gap

•this event corresponds to the complete closure of the vocal tract

•minimum radiated acoustic energy

•silence for voiceless stops

•voice bar for voiced stops

•50 - 150 ms

•Stop gap

•this event corresponds to the complete closure of the vocal tract

•minimum radiated acoustic energy

•silence for voiceless stops

•voice bar for voiced stops

•50 - 150 ms

Stop Consonants (3)Stop Consonants (3)• Stop release (burst)

• pressure has been rising behind the obstruction

• rapid release produces a transient

• 20 - 30 ms

• thus, suitable temporal resolution is needed

• voiceless stops follow the burst with frication

• noise generated at the place of articulation

• low frequency for /p/ (500 - 1500 Hz) (falling spectrum)

• high frequency for /t/ (above 4 kHz) (rising spectrum)

• mid-frequency for /k/ (1.5 - 4 kHz) (peaked spectrum)

• Stop release (burst)

• pressure has been rising behind the obstruction

• rapid release produces a transient

• 20 - 30 ms

• thus, suitable temporal resolution is needed

• voiceless stops follow the burst with frication

• noise generated at the place of articulation

• low frequency for /p/ (500 - 1500 Hz) (falling spectrum)

• high frequency for /t/ (above 4 kHz) (rising spectrum)

• mid-frequency for /k/ (1.5 - 4 kHz) (peaked spectrum)

Stop Consonants (4) Stop Consonants (4) •Cues for voicing

•/p t k/ are phonetically distinguished from /b d g/ by voicing

•VOT is the interval between the release of the stop and the onset of vocal fold vibration

•for /b d g/ VOT from -20 to +20 ms with a mean of 10 ms

•for /p t k/ VOT from 25 to 80 ms with a mean of 45 ms

•voice bar for intervocalic stops

•length of preceding vowel for final stops

•Cues for voicing

•/p t k/ are phonetically distinguished from /b d g/ by voicing

•VOT is the interval between the release of the stop and the onset of vocal fold vibration

•for /b d g/ VOT from -20 to +20 ms with a mean of 10 ms

•for /p t k/ VOT from 25 to 80 ms with a mean of 45 ms

•voice bar for intervocalic stops

•length of preceding vowel for final stops

Stop Consonants (5)Stop Consonants (5)

•Formant transitions

•articulatory movement from stop to vowel entails a formant movement

•as the resonating chamber of the vocal tract changes, the formant frequencies change

•formant transitions are important for perception

•formant transitions are approximately 50 ms in duration

•Formant transitions

•articulatory movement from stop to vowel entails a formant movement

•as the resonating chamber of the vocal tract changes, the formant frequencies change

•formant transitions are important for perception

•formant transitions are approximately 50 ms in duration

Stop Consonants (6)Stop Consonants (6)•Formant transitions (continued)

•F1 usually rises for the stop consonants

•F2 and F3 are not so simple

• for /p b/ F2 and F3 rise slightly

• for /t d/ F2 falls and F3 rises slightly

• for /k g/ F2 and F3 separate steeply and rapidly

•However, a given stop is associated with a variety of transitions (see Fig. 5-14)

•there is no fixed transition pattern for perception

•Cue trading in stop consonants

•Formant transitions (continued)

•F1 usually rises for the stop consonants

•F2 and F3 are not so simple

• for /p b/ F2 and F3 rise slightly

• for /t d/ F2 falls and F3 rises slightly

• for /k g/ F2 and F3 separate steeply and rapidly

•However, a given stop is associated with a variety of transitions (see Fig. 5-14)

•there is no fixed transition pattern for perception

•Cue trading in stop consonants

FricativesFricatives•Articulation

•Narrow constriction in the vocal tract

•When air flow rate is high, turbulence results

•Turbulence is complex, unpredictable air flow

•Turbulent airflow is perceived as turbulent noise

•Fricatives have a relatively long duration

•Fricatives are divided into

•sibilants (stridents)

•nonsibilants (nonstridents)

•Articulation

•Narrow constriction in the vocal tract

•When air flow rate is high, turbulence results

•Turbulence is complex, unpredictable air flow

•Turbulent airflow is perceived as turbulent noise

•Fricatives have a relatively long duration

•Fricatives are divided into

•sibilants (stridents)

•nonsibilants (nonstridents)

Fricatives (2)Fricatives (2)• Sibilants

• Intense noise

• Differentiated among themselves by

• voicing

• noise spectrum

• Voicing

• pulses (glottal closures) for /z ʒ/

• no pulses for /s ʃ/

• Noise spectrum

• Alveolar sibilants have higher frequency energy

• Palatal sibilants have energy down to 3 kHz

• Spectral irregularities aren’t important in perception

• Formant transitions

• Formant transition locations depend on the articulation, but the transitions are not important perceptually for sibilants

• Sibilants

• Intense noise

• Differentiated among themselves by

• voicing

• noise spectrum

• Voicing

• pulses (glottal closures) for /z ʒ/

• no pulses for /s ʃ/

• Noise spectrum

• Alveolar sibilants have higher frequency energy

• Palatal sibilants have energy down to 3 kHz

• Spectral irregularities aren’t important in perception

• Formant transitions

• Formant transition locations depend on the articulation, but the transitions are not important perceptually for sibilants

Fricatives (3)Fricatives (3)•Nonsibilants /f v θ ð h/

•Less noise energy than sibilants

•Voiced nonsibilants will have quasi-periodic pulses

•Noise spectra are

• fairly flat

•diffuse

•The relationship between noise spectrum nonsibilant identification is not known

•Formant transitions play the primary role in perception

•Noise spectrum may play a secondary role

•Nonsibilants /f v θ ð h/

•Less noise energy than sibilants

•Voiced nonsibilants will have quasi-periodic pulses

•Noise spectra are

• fairly flat

•diffuse

•The relationship between noise spectrum nonsibilant identification is not known

•Formant transitions play the primary role in perception

•Noise spectrum may play a secondary role

Fricatives (4)Fricatives (4)•Acoustical needs for fricatives

•Measures that are economical

•Economical

•Valid

•Reliable

•Problems

•Ambient noise

•Filtering values

•Acoustical needs for fricatives

•Measures that are economical

•Economical

•Valid

•Reliable

•Problems

•Ambient noise

•Filtering values

AffricatesAffricates• Described as a combination of stop and fricative

• /ʧ ʤ/

• Articulation

• complete obstruction in the vocal tract

• intraoral pressure builds up

• release to generate fricative noise

• Acoustic features

• rise time

• duration of frication

• relative amplitude in third formant region

• stop gap

• Described as a combination of stop and fricative

• /ʧ ʤ/

• Articulation

• complete obstruction in the vocal tract

• intraoral pressure builds up

• release to generate fricative noise

• Acoustic features

• rise time

• duration of frication

• relative amplitude in third formant region

• stop gap

NasalsNasals• Articulation

• complete closure in vocal tract

• sound radiated through nasal cavities

• sometimes called nasal stops

• /m n ŋ/

• Acoustics

• Nasal murmur - sound of a nasal

• associated strictly with nasal radiation of sound

• there are many spectral peaks, but most have low amplitude

• antiformants

• nasal formant

• low frequency (~300 Hz)

• highest energy

• Articulation

• complete closure in vocal tract

• sound radiated through nasal cavities

• sometimes called nasal stops

• /m n ŋ/

• Acoustics

• Nasal murmur - sound of a nasal

• associated strictly with nasal radiation of sound

• there are many spectral peaks, but most have low amplitude

• antiformants

• nasal formant

• low frequency (~300 Hz)

• highest energy

Nasals (2)Nasals (2)

•Nasal formant (continued)

•consonant energy, overall, is reduced because

•higher formants have reduced energy

•Other acoustic features

•highly damped formants (broad bandwidths)

•formant transitions in connected speech

•Nasal formant (continued)

•consonant energy, overall, is reduced because

•higher formants have reduced energy

•Other acoustic features

•highly damped formants (broad bandwidths)

•formant transitions in connected speech

Glide ConsonantsGlide Consonants• Also called approximants and semivowels

• /w ʲ/

• Articulation

• gradual articulatory motion

• narrow, but not closed, vocal tract

• Acoustics

• Formants

• for /w/

• F1 and F2 are both low

• for /ʲ/

• low F1 and high F2

• Also called approximants and semivowels

• /w ʲ/

• Articulation

• gradual articulatory motion

• narrow, but not closed, vocal tract

• Acoustics

• Formants

• for /w/

• F1 and F2 are both low

• for /ʲ/

• low F1 and high F2

Liquid ConsonantsLiquid Consonants

•Also included as semivowels

•/ɹ l/

•Characterized by

•rapid movements

•formant structure

•F3 is the main difference

•Antiformants for /l/

•Also included as semivowels

•/ɹ l/

•Characterized by

•rapid movements

•formant structure

•F3 is the main difference

•Antiformants for /l/