1. Effect of Word Frequency on Tonal Variation Yuan Zhao, Dan Jurafsky Stanford University
ABSTRACT
We show that lexical frequency is an important source of tonal variation. Words of low (corpus) frequency are produced with higher f0 than high-frequency words of the same tone. Our results suggest that phonetic context is not the only source of tonal variation. Surface realization of tone is also affected by lexical factors like word frequency.
RESULTS
Low-frequency words have higher f0
Frequency effect is on mid-tones
Tone3 (mid-level): LF 11.7 Hz higher than HF words
(F (1,7) = , p<.002);
Tone5 (mid/low-rising): LF 7.5 Hz higher than HF words
(F (1,7) = , p<.010).
Frequency effect not constant during word
Lexical frequency starts influencing tonal variation only 50% of the way through the word, (no significant effect on tone production at beginning of word)
INTRODUCTION
Background: We know lexical frequency influences segmental realization:
LF words: fuller vowels (Fidelholtz, Rhodes, Bybee, etc)
LF words: expanded vowel space (Munson 200)
Question: Does lexical frequency influence the surface realization of tones?
Hypothesis I: HF and LF words of the same lexical tone will be produced at different pitch (f0).
Hypothesis II: Tonal contrast among close competing tones will increase when speakers produce LF words (vide Lindblom H&H)
DATA
Test Language: Cantonese (6-tones)
Materials: 90 HF and LF monosyllabic word pairs
Balanced for tones and segmental content
Above 6 on familiarity scale
Frequency: mean HF= 3.66; mean LF=0.97
Speaker: 8 Hong Kong Cantonese speakers
Measurement: f0 value at 10 equidistant points
Tonal contrast of LF words increases
Tonal Distance=
F0 of six tones
CONCLUSIONS
There is systematic subphonemic variation in tone production due to the lexical status of words
LF words are produced at higher f0 than HF words of the same tone
Lexical frequency doesn’t start influencing tone production until half way through the word
Clearer tone production of LF words: tonal contrast of LF words is larger than that of HF words;