Automatic evaluation of prosodic features of tracheoesophageal substitute voice

In comparison with laryngeal voice, substitute voice after laryngectomy is characterized by restricted aero-acoustic properties. Until now, an objective means of prosodic differences between substitute and normal voices does not exist. In a pilot study, we applied an automatic prosody analysis module to 18 speech samples of laryngectomees (age: 64.2 +/- 8.3 years) and 18 recordings of normal speakers of the same age (65.4 +/- 7.6 years). Ninety-five different features per word based upon the speech energy, fundamental frequency F(0) and duration measures on words, pauses and voiced/voiceless sections were measured. These reflect aspects of loudness, pitch and articulation rate. Subjective evaluation of the 18 patients' voices was performed by a panel of five experts on the criteria "noise", "speech effort", "roughness", "intelligibility", "match of breath and sense units" and "overall quality". These ratings were compared to the automatically computed features. Several of them could be identified being twice as high for the laryngectomees compared to the normal speakers, and vice versa. Comparing the evaluation data of the human experts and the automatic rating, correlation coefficients of up to 0.84 were measured. The automatic analysis serves as a good means to objectify and quantify the global speech outcome of laryngectomees. Even better results are expected when both the computation of the features and the comparison method to the human ratings will have been revised and adapted to the special properties of the substitute voices.