Measures Of Cepstral Peak Prominence Research Articles

Spectral- and Cepstral-Based Measures During Continuous Speech: Capacity to Distinguish Dysphonia and Consistency Within a Speaker

Spectral- and cepstral-based acoustic measures are preferable to time-based measures for accurately representing dysphonic voices during continuous speech. Although these measures show promising relationships to perceptual voice quality ratings, less is known regarding their ability to differentiate normal from dysphonic voice during continuous speech and the consistency of these measures across multiple utterances by the same speaker. The purpose of this study was to determine whether spectral moments of the long-term average spectrum (LTAS) (spectral mean, standard deviation, skewness, and kurtosis) and cepstral peak prominence measures were significantly different for speakers with and without voice disorders when assessed during continuous speech. The consistency of these measures within a speaker across utterances was also addressed. Continuous speech samples from 27 subjects without voice disorders and 27 subjects with mixed voice disorders were acoustically analyzed. In addition, voice samples were perceptually rated for overall severity. Acoustic analyses were performed on three continuous speech stimuli from a reading passage: two full sentences and one constituent phrase. Significant between-group differences were found for both cepstral measures and three LTAS measures (P<0.001): spectral mean, skewness, and kurtosis. These five measures also showed moderate to strong correlations to overall voice severity. Furthermore, high degrees of within-speaker consistency (correlation coefficients ≥0.89) across utterances with varying length and phonemic content were evidenced for both subject groups.

An acoustic and electroglottographic study of phonation contrast in Yi.

This study examines the phonation contrast of Yi, a Tibeto-Burman language of Southwestern China with phonation as a phonemic dimension (traditionally described as tense versus lax contrast). The language has seven monophthongs as well as three tones (high, mid, and low). Tense versus lax phonation contrast can apply to all the vowels and two tones (mid and low) in the language. In this study, both acoustic and electroglottographic data were collected with minimal pairs for all combinations of tones and vowels. Extensive acoustic measures were done by VOICESAUCE, including F0, H1, H2, H1-H2, H2-H4, H1-A1, H1-A2, F1, F2, and cepstral peak prominence (CPP); EGG measures were closed quotient (CQ) and peak-velocity (PV). Preliminary data suggest that H1-H2, CPP, CQ, and PV measures can exclusively distinguish the two phonation types. Moreover, EGG data also suggest voice quality interacts with tones, but the patterns vary among speakers. This might due to the different strategies used by speakers to produce the tense versus lax contrast. In addition, formant frequency measures also show salient differences between tense and lax vowels; tense vowels generally have higher F1 than the lax counterparts. All of the facts suggest that phonation contrasts in Yi are realized across different phonetic dimensions.

Kinematic modeling and acoustic measures of breathy voice.

A variety of disordered vocal fold structural and vibratory parameters have been identified in patients with breathy dysphonia, although the contribution of each parameter to voice quality is unknown. This study is part of an effort to determine the relation between production and voice quality. A kinematic vocal fold model [based on I. R. Titze, Speech Commun., 8, 191–201 (1989)] that emulates the medial surface of the vocal folds was used to ascertain factors that lead to breathy voice. Based on the ratings of four expert listeners, five parameters were selected for further study. Combinations of multiple levels of adduction, bulging, nodal point, epilaryngeal area, and phase were used to generate 180 samples of sustained /ɑ/ and /ɪ/. Seven acoustic analyses were performed for each sample: maximum flow declination rate, maximum area declination rate, two measures of H1-H2, two measures of cepstral peak prominence, and noise to harmonics ratio. All parameters led to systematic changes in acoustic measures reflecting increasing breathiness, with several inconsistencies highlighting the uniqueness of each measure. The H1-H2 measures were inconsistent with the other data. Results will be described in light of how each measure can inform researchers about production. [Work supported in part by NIH R01-DC04789.]

The Effect of Perceptual Training on Inexperienced Listeners' Judgments of Dysphonic Voice

The purpose of this study was (1) to determine whether changes in intra- and interrater reliability occur for inexperienced listeners' judgments of overall severity, roughness, and breathiness in dysphonic and normal speakers after 2 hours of listener training; and (2) to determine the acoustic bases of inexperienced listeners' judgments before and after training. Prospective, single group, pre- and postdesign. Thirty adult dysphonic and six normal speaker samples were selected from a database. Samples included 21 test stimuli and 15 training stimuli of both sustained vowels and connected speech. Sixteen inexperienced listeners judged all samples for overall severity, roughness, and breathiness using visual analog scales. Each listener provided pretraining ratings at baseline. Listeners were then trained using 15 anchor voice samples and 15 training stimuli. During training, listeners were provided with definitions of rating dimensions, accuracy feedback, and anchor samples. Listeners then judged test stimuli in a posttraining session. Speaker samples also were analyzed acoustically. Intrarater reliability was least variable for judgments of overall severity, but improved further with training. Listener judgments of roughness and breathiness in vowels were least reliable at baseline, but they significantly improved between listeners after training. Finally, measures of cepstral peak prominence significantly predicted all voice quality judgments except roughness in vowels, which was predicted by shimmer. The acoustic bases of group perceptual judgments did not seem to change with training. These findings have implications for developing training programs in perceptual evaluation and mapping relationships between acoustic and perceptual characteristics of voice disorders.

Reliability of calculating the cepstral peak without linear regression analysis

Summary Measures of cepstral peak prominence, using the smoothing algorithm and linear regression analysis software developed by Hillenbrand, have been shown to be reliable predictors of dysphonia in voice samples. 1–4 Recently, the Computerized Speech Laboratory [(CSL) Kay Elemetrics, Pinebrook, New Jersey] has introduced cepstral analysis as a component of that software package. The cepstral peak, in this instance, is calculated by the voice clinician analyzing the phonatory sample by subtracting the value of the peak from the apparent baseline signal. This study compares the ability of cepstral peak values calculated from the CSL software to predict dysphonia reliably with that of the values produced by the smoothing algorithm and linear regression analysis of Hillenbrand. The results of this study show that linear regression analysis is an important step in calculating the cepstral peak prominence, thus limiting the usefulness of software programs that do not employ this step.

Cepstral peak prominence: a more reliable measure of dysphonia.

Quantification of perceptual voice characteristics allows the assessment of voice changes. Acoustic measures of jitter, shimmer, and noise-to-harmonic ratio (NHR) are often unreliable. Measures of cepstral peak prominence (CPP) may be more reliable predictors of dysphonia. Trained listeners analyzed voice samples from 281 patients. The NHR, amplitude perturbation quotient, smoothed pitch perturbation quotient, percent jitter, and CPP were obtained from sustained vowel phonation, and the CPP was obtained from running speech. For the first time, normal and abnormal values of CPP were defined, and they were compared with other acoustic measures used to predict dysphonia. The CPP for running speech is a good predictor and a more reliable measure of dysphonia than are acoustic measures of jitter, shimmer, and NHR.

The Relationship Between Cepstral Peak Prominence and Selected Parameters of Dysphonia

Traditional measures of dysphonia vary in their reliability and in their correlations with perceptions of grade. Measurements of cepstral peak prominence (CPP) have been shown to correlate well with perceptions of breathiness. Because it is a measure of periodicity, CPP should also predict roughness. The ability of CPP and other acoustic measures to predict overall dysphonia and the subcategories of breathiness and roughness in pathological voice samples is explored. Preoperative and postoperative speech samples from 19 patients with unilateral recurrent laryngeal nerve paralysis who underwent operative intervention were analyzed by trained listeners and by measures of smoothed CPP (CPPS), noise-to-harmonic ratio (NHR), amplitude perturbation quotient (APQ), relative average perturbation (RAP), and smoothed pitch perturbation quotient (sPPQ). The data were analyzed with bivariate Pearson correlation statistics. Grade of dysphonia and breathiness ratings correlated better with measurements of CPPS than with the other measures. CPPS from samples of connected speech (CPPS-s) best predicted overall dysphonia. None of the measures were useful in predicting roughness.