Nonlinear Dynamical Analysis of Laryngeal, Esophageal, and Tracheoesophageal Speech of Cantonese

The use of the Lombard Effect in Improving Alaryngeal Speech

OBJECTIVE

The present study examined and compared the Lombard effect among laryngeal and alaryngeal speakers including esophageal, tracheoesophageal, pneumatic artificial laryngeal, electrolaryngeal speakers of Cantonese. The subsequent change in intelligibility was also examined.

METHODS

A total of 52 native Cantonese-speaking laryngeal and alaryngeal speakers (10 laryngeal , 8 laryngeal , 13 electrolaryngeal , 11 esophageal, and 10 tracheoesophageal) participated in a reading task involving three 10-syllable Cantonese sentences under 10 background conditions: quiet, 60 dB, 65 dB, 70 dB, 75 dB, 80 dB, 85 dB, 90 dB, 95 dB, and 100 dB white background noise. Speech intelligibility associated with speaking conditions were evaluated by five naïve Cantonese speakers.

RESULTS

Output intensity was significantly increased in all speaker types under all nine noisy background conditions when compared with the quiet condition. However, the amount of increase was different for different modes of phonation. In addition, significant difference in speech intelligibility between laryngeal and alaryngeal speakers was found at all conditions, but not among any alaryngeal speech.

DISCUSSION AND CONCLUSION

The Lombard reflex is still present after total laryngectomy. Yet, different alaryngeal speech was associated with different amount of loudness change, and subsequent improvement in intelligibility was not observed.

An Acoustic Study of Vowels Produced by Alaryngeal Speakers in Taiwan

PURPOSE

This study investigated the acoustic properties of 6 Taiwan Southern Min vowels produced by 10 laryngeal speakers (LA), 10 speakers with a pneumatic artificial larynx (PA), and 8 esophageal speakers (ES).

METHOD

Each of the 6 monophthongs of Taiwan Southern Min (/i, e, a, ɔ, u, ə/) was represented by a Taiwan Southern Min character and appeared randomly on a list 3 times (6 Taiwan Southern Min characters × 3 repetitions = 18 tokens). Each Taiwan Southern Min character in this study has the same syllable structure, /V/, and all were read with tone 1 (high and level). Acoustic measurements of the 1st formant, 2nd formant, and 3rd formant were taken for each vowel. Then, vowel space areas (VSAs) enclosed by /i, a, u/ were calculated for each group of speakers. The Euclidean distance between vowels in the pairs /i, a/, /i, u/, and /a, u/ was also calculated and compared across the groups.

RESULTS

PA and ES have higher 1st or 2nd formant values than LA for each vowel. The distance is significantly shorter between vowels in the corner vowel pairs /i, a/ and /i, u/. PA and ES have a significantly smaller VSA compared with LA.

CONCLUSIONS

In accordance with previous studies, alaryngeal speakers have higher formant frequency values than LA because they have a shortened vocal tract as a result of their total laryngectomy. Furthermore, the resonance frequencies are inversely related to the length of the vocal tract (on the basis of the assumption of the source filter theory). PA and ES have a smaller VSA and shorter distances between corner vowels compared with LA, which may be related to speech intelligibility. This hypothesis needs further support from future study.