Technical considerations in computation of spectral harmonics-to-noise ratios for sustained vowels

This paper explores technical issues affecting computed measures of the relative level of noise in the frequency spectrum of a vowel. This type of measure has been proposed for quantification of hoarseness in pathological speakers. An analysis of synthesized vowels was used to test the influence of vowel type, fundamental frequency, perturbation type, perturbation level and quantization. The algorithms were shown to be highly sensitive to errors in pitch-period demarcation, and a dependency on jitter perturbations, fundamental frequency, and vowel type was demonstrated. Relationships between algorithm performance and methods of spectrum estimation were discussed, and approaches for reducing the dependencies were proposed. Finally, a method for achieving a significant reduction in computation time was described.     

Acoustic discrimination of pathological voice: sustained vowels versus continuous speech.

We investigated the ability of acoustic measures to discriminate between normal and pathological talkers. Two groups of measures were compared: (a) those extracted from sustained vowels and (b) those based on continuous speech samples. Nine acoustic measures, which include fundamental frequency and amplitude perturbation measures, long term average spectral measures, and glottal noise measures were extracted from both sustained vowel and continuous speech samples. Our experiments were performed on a published database of 53 normal talkers and 175 talkers with a pathological voice. The classification performance of the nine acoustic measures was quantified using linear discriminant analysis and receiver operating characteristic (ROC) curve analysis. When individual measures were considered in isolation, classification was more accurate for measures extracted from sustained vowels than for those based on continuous speech samples. Classification accuracy improved when combinations of acoustic parameters were considered. For such combinations of measures, classification results were comparable for measures extracted from continuous speech samples and for those based on sustained vowels.     

Comparison of the F0F2 and F0F1F2 processing strategies for the Cochlear Corporation cochlear implant

In April 1985, an updated processing strategy became available for the Cochlear Corporation Nucleus cochlear implant. Whereas the original strategy codes only fundamental frequency, amplitude, and information in the second formant region, the newer strategy also codes frequencies in the first formant region. This investigation evaluated the speech recognition skills of five subjects who were experienced with both designs. On average, the addition of first formant information improved word identification in an audition-only condition and improved spondee recognition in noise. Scores for the NU 6 Monosyllabic Word Test and the Sentence Test Without Context improved from 8% (2-12%) to 28% words correct (10-42%), and from 31% (10-45%) to 64% words correct (39-84%), respectively. Scores for the Four-Choice Spondee Test in noise improved from 37% (25-50%) to 75% (45-90%). The percent correct scores for the Iowa 14-Item Consonant Confusion Test in an audition-only and vision-plus-audition condition did not vary with the change in processing strategy. However, an information transfer analysis performed on the responses to the consonant test in a vision-only and a vision-plus-audition condition suggested that the newer strategy enhances the transmission of the voicing, duration, and envelope features.     

Short-latency changes in voice F0 and neck surface EMG induced by mechanical perturbations of the larynx during sustained vowel phonation.

Nineteen healthy young adult males with normal voice and speech attempted to sustain the vowel /u/ at a constant pitch (target: 180 Hz) and a constant and comfortable loudness level while receiving a sudden mechanical perturbation to the larynx (thyroid prominence) via a servo-controlled probe. The probe moved toward or away from the larynx in a ramp-and-hold fashion (3.3-mm displacement, 0.7 N force, 20-ms rise time, 250-ms duration) as the subjects attempted to maintain a constant probe-larynx pressure. Eighty stimuli were applied in each direction, one stimulus per phonation. Pairs of surface electromyography (EMG) electrodes were attached to the skin of the anterior neck over laryngeal, infralaryngeal, and supralaryngeal areas. The rectified EMG signals, the voltage analog of the voice fundamental frequency (VAF0), and the voltage analog of the probe displacement were digitized and signal-averaged relative to the onset of the stimulus. Sudden perturbation of the larynx induced an instantaneous decrease or increase in VAF0, depending on the direction of the probe's movement, and a short-latency increase in the EMG (30-35 ms) and VAF0 (55-65 ms). We argue that the instantaneous VAF0 change was related to a mechanical effect, and the short-latency VAF0 and EMG changes to reflexogenic effects-the latter most likely associated with both intrinsic and extrinsic laryngeal sensorimotor mechanisms. Further physiological studies are needed to elucidate the sources of the VAF0 and EMG responses. Once elucidated, the present method may provide a powerful noninvasive tool for studying laryngeal neurophysiology. The theoretical and clinical implications of the present findings are addressed.     

Consistency of fundamental frequency and perturbation in repeated phonations of sustained vowels, reading, and connected speech

The purpose of this study was to determine consistency of the acoustic measurement of fundamental frequency (f0) and f0 perturbation using the Visi-Pitch. Samples of speech including a reading passage, vowels, and spontaneous speech were recorded for 12 normal young adults (6 men and 6 women). The results indicated that test-retest reliability was highest for the reading passage. The measurements of fundamental frequency for reading and spontaneous speech were very similar, but vowel production was, on average, higher in frequency than the other contexts. Test-retest measures of perturbation using the Visi-Pitch did not have a high correlation coefficient. Perturbation measures must be interpreted cautiously because of the influence of frequency.     

The acquisition of unrounded vowels in English.

This study investigated developmental patterns of acquisition of the unrounded American English vowels /i, I, e, e, ae, a/ by following 6 normally developing children from 22 to 30 months of age. The subjects were examined at approximately 22, 26, and 30 months of age. Results showed that, in general, /i/ and /a/ were mastered early and /I/ and /e/ were least accurate throughout the period of the study. Upon inspection of errors, the following three classes of production errors were identified: (a) intertrial production variability, (b) context-sensitive substitutions, and (c) context-free systematic substitution patterns, or articulatory processes. A decrease in production variability and in the occurrence of articulatory processes with age generally coincided with a gradual improvement in accuracy of production. However, substitutions of lower vowels for /I/ were persistent, and the pattern was observed even at 30 months of age. Individual variation was also evident in the production accuracy, the substitution patterns, and the manner of articulatory improvement.     

Acoustic and perceptual parameters relating to connected speech are more reliable measures of hoarseness than parameters relating to sustained vowels

This report investigates the correlations between acoustic parameters and the perception of hoarseness by trained listeners. Both sustained vowels and connected speech were examined. Fourteen acoustic parameters from samples of sustained vowels and 2 from connected speech were measured. The results show that jitter, shimmer and cepstral peak prominence (CPP) are correlated with the perception of hoarseness in sustained vowels. CPP is strongly correlated with the perception of hoarseness in connected speech. Some evidence is seen that perception of hoarseness in connected speech is more valid than the perception of hoarseness in sustained vowels. It is concluded that CPP for connected speech is a more valid objective measure of hoarseness than jitter, shimmer or CPP for sustained vowels and that perception of hoarseness may be most accurate in connected speech, rather than isolated vowels.     

A precision technique for suprahyoid pharyngotomy

This technique of suprahyoid pharyngotomy is very useful for excision of selected laryngeal and pharyngeal neoplasms. By identifying and following the hyoepiglottic ligament, precise entry into the pharynx is accomplished easily and rapidly at the median glossoepiglottic fold.     

Acoustical analysis of Spanish vowels produced by laryngectomized subjects.

The purpose of this study was to describe the acoustic characteristics of Spanish vowels in subjects who had undergone a total laryngectomy and to compare the results with those obtained in a control group of subjects who spoke normally. Our results are discussed in relation to those obtained in previous studies with English-speaking laryngectomized patients. The comparison between English and Spanish, which diFfer widely in the size of their vowel inventories, will help us to determine specific or universal vowel production characteristics in these patients. Our second objective was to relate the acoustic properties of these vowels to the perceptual data obtained in our previous work (J. L. Miralles & T. Cervera, 1995). In that study, results indicated that vowels produced by alaryngeal speakers were well perceived in word context. Vowels were produced in CVCV word context by two groups of patients who had undergone laryngectomy: tracheoesophageal speakers (TES) and esophageal speakers. In addition a control group of normal talkers was included. Audio recordings of 24 Spanish words produced by each speaker were analyzed using CSL (Kay Elemetrics). Results showed that F1, F2, and vowel duration of alaryngeal speakers differ significantly from normal values. In general, laryngectomized patients produce vowels with higher formant frequencies and longer durations than the group of laryngeal subjects. Thus, the data indicate modifications either in the frequency or temporal domain, following the same tendency found in previous studies with English-speaking laryngectomized speakers.     

Effect of age on F0 difference limen and concurrent vowel identification.

PURPOSE: To investigate the effect of age on voice fundamental frequency (F0) difference limen (DL) and identification of concurrently presented vowels. METHOD: Fifteen younger and 15 older adults with normal audiometric thresholds in the speech range participated in 2 experiments. In Experiment 1, F0 DLs were measured for a synthesized vowel. In Experiment 2, accuracy in identifying concurrently presented vowel pairs was measured. Vowel pairs were formed from 5 synthesized vowels with F0 separations ranging from 0 to 4 semitones. RESULTS: Younger adults had smaller (better) F0 DLs than older adults. For the older group, age was significantly correlated with F0 DLs. Younger adults identified concurrent vowels more accurately than older adults. When the vowels in the pairs had different formants, both age groups benefited similarly from F0 separation. Interestingly, when both constituent vowels had identical formants, F0 separation was deleterious, especially for older adults. Pure-tone average threshold did not correlate significantly with either F0 DL or accuracy in concurrent vowel identification. CONCLUSION: Age-related declines were confirmed for F0 DLs, identification of concurrently spoken vowels, and benefit from F0 separation between vowels with identical formants. This pattern of findings is consistent with age-related deficits in periodicity coding.     

Intelligibility of vowels produced by post-lingually deafened cochlear implant users.

The present study addresses the effect of cochlear implantation on the intelligibility of vowels produced by 20 post-lingually deafened Dutch subjects. All subjects received the Nucleus-22 cochlear implant (3 WSP and 17 MSP processors). Speech recordings were made pre-implantation and three and twelve months post-implantation with the implant switched on and off. Vowel intelligibility (monophthongs only) was determined using a panel of listeners. For all implanted subjects intelligibility was measured in a noisy background. For seven poorly speaking subjects it was also measured in a quiet background. After implantation with the Nucleus-22 device the results showed that vowel intelligibility, measured for all subjects in a noisy background, increased for most of them (about 15), while it increased for about half the number of poorly speaking subjects measured in a quiet background. Twelve months after implantation vowel intelligibility, measured for all subjects in noise, appeared to be based on first and second formant information. This was also found for the subgroup of seven subjects performing poorly pre-implantation when analysed separately. However, vowel intelligibility for this subgroup, when measured in a quiet background, was based also on vowel duration. The differences between the overall result in noise and the results of the subgroup in quiet should be attributed mainly to the noise and not to aspects of poor speech production in the subgroup. In addition, this study addresses the relationship between the intelligibility scores and objective measurements of vowel quality performed in a previous study. The results showed that the vowel intelligibility scores are mainly determined by the position of the second formant frequencies.     

The effect of hearing loss on identification of asynchronous double vowels.

This study determined whether listeners with hearing loss received reduced benefits due to an onset asynchrony between sounds. Seven normal-hearing listeners and 7 listeners with hearing impairment (HI) were presented with 2 synthetic, steady-state vowels. One vowel (the late-arriving vowel) was 250 ms in duration, and the other (the early-arriving vowel) varied in duration between 350 and 550 ms. The vowels had simultaneous offsets, and therefore an onset asynchrony between the 2 vowels ranged between 100 and 300 ms. The early-arriving and late-arriving vowels also had either the same or different fundamental frequencies. Increases in onset asynchrony and differences in fundamental frequency led to better vowel-identification performance for both groups, with listeners with HI benefiting less from onset asynchrony than normal-hearing listeners. The presence of fundamental frequency differences did not influence the benefit received from onset asynchrony for either group. Excitation pattern modeling indicated that the reduced benefit received from onset asynchrony was not easily predicted by the reduced audibility of the vowel sounds for listeners with HI. Therefore, suprathreshold factors such as loss of the cochlear nonlinearity, reduced temporal integration, and the perception of vowel dominance probably play a greater role in the reduced benefit received from onset asynchrony in listeners with HI.     

A comparison of methods for nasal mast cell demonstration.

Nasal turbinates were studied from 14 rhinitis patients following surgical turbinectomy, and from five subjects at autopsy. Mast cell counts on turbinectomy specimens were compared following staining with toluidine blue or Alcian blue and safranin after fixation in either paraformaldehyde or neutral buffered formalin. Mast cell numbers were significantly greater in the superficial submucosa than in the epithelium or deep submucosa in both the rhinitis group and the autopsy subjects. The combination of PFA fixation and ABS staining gave maximum mast cell counts, revealed two morphological mast cell sub-types and gave optimal demonstration of nasal tissue. Nasal mast cells are thus not uniformly distributed, appear heterogeneous under light microscopy, are present in large numbers even in the elderly, and are best demonstrated using PFA fixation and ABS staining.     

Acoustical-perceptual correlates of "whisper pitch" in synthetically generated vowels.

The purpose of this investigation was to clarify acoustical-perceptual relationships in identification of "pitch" during whispered vowel production. The experimenters systematically varied selected acoustic features of synthetically generated "whispered" vowels to control which formant frequencies were shifted (F1, F2, or F1&F2), the direction of formant frequency shifts (up or down), and the magnitude of formant frequency shifts (20 Hz, 40 Hz, 60 Hz). Two sets of stimuli were produced to simulate the resonance characteristics of the vowel /a/: one set for male talkers and one for female talkers. Ninety-four pairs of synthesized vowel tokens were randomly presented to 17 listeners who judged if the "pitch" of the second member of the pair was the same, higher, or lower than the "pitch" of the first member. The results showed an inverse relationship between the magnitude of formant frequency changes presented to the judges and the number of perceptual mismatches in "whisper pitch." Also, fewer mismatches in the identification of whisper pitch occurred when both F1 and F2 were changed simultaneously than when either F1 or F2 was changed individually. No differences were found between the perceptual responses to "male" and "female" vowel simulations. The primary implication of this study is that whisper pitch is more influenced by simultaneous changes in F1 and F2 than by changes in only one of the formants.     

F. N. A. C. of salivary glands

During a period of 12 years, 874 salivary gland lesions were aspirated of which 740 (86.85%) were from parotid gland. Cystic, inflammatory & neoplastic lesions were 25.25%. 54.45% & 20.30%, respectively. Plcomorphic adenoma was the commonest benign & adenoid cystic carcinoma was the most frequent malignant tumors. On cytohistologic correlation, sensilitvity of cytology for diagnosing cystic, inflammatory, neoplastic lesions proved to be 93.3%. 95.7% & 100% respectively. Overall accuracy for cytodiagnosis of malignant salivary gland lesions in our study was 96.07%.     

New strategies for high precision surgery of the temporal bone using a robotic approach for cochlear implantation

The aim of the study was to demonstrate a collision-free trajectory of an instrument through the facial recess to the site of planned cochleostomy guided by a surgery robot. The indication for cochlear implantation is still expanding toward more substantial residual hearing. A cochleostomy as atraumatic as possible will influence the preservation of inner ear function. The employment of a highly precise instrument guidance using a robot could represent a feasible solution for a constant reproducible surgical procedure. Screw markers for a point-based registration were fixed on a human temporal bone specimen prepared with a mastoidectomy and posterior tympanotomy. A DICOM dataset has been generated thereof in a 64-multislice computer tomography (CT). A virtual trajectory in a 3D model has been planned representing the path of instrumentation toward the desired spot of cochleostomy. A 1.9-mm endoscope has been mounted onto the robot system RobaCKa (Staeubli RX90CR) to visualize this trajectory. The target registration error added up to 0.25 mm, which met the desirable tolerance of <0.5 mm. A collision-free propagation of the endoscope into the tympanic cavity via the facial recess has been performed by the robot and the spot of cochleostomy could be visualized through the endoscope. Using a DICOM dataset of a high-resolution CT and a robot as a positioning platform for surgical instruments could be a feasible approach to perform a highly precise and constant reproducible cochleostomy. Furthermore, it could be a crucial step to preserve substantial residual hearing in terms of expanding the indications for cochlear implantation. This paper was presented at the 79th Annual Meeting of the German Society of Otorhinolaryngology, Head and Neck Surgery, Erfurt, May 2005, and at the 9th International Conference on Cochlear Implants and Related Sciences, Vienna, June 2006.