Robust classification with context-sensitive features

This paper addresses the problem of classifying observations when features are context-sensitive, especially when the testing set involves a context that is different from the training set. The paper begins with a precise definition of the problem, then general strategies are presented for enhancing the performance of classification algorithms on this type of problem. These strategies are tested on three domains. The first domain is the diagnosis of gas turbine engines. The problem is to diagnose a faulty engine in one context, such as warm weather, when the fault has previously been seen only in another context, such as cold weather. The second domain is speech recognition. The context is given by the identity of the speaker. The problem is to recognize words spoken by a new speaker, not represented in the training set. The third domain is medical prognosis. The problem is to predict whether a patient with hepatitis will live or die. The context is the age of the patient. For all three domains, exploiting context results in substantially more accurate classification

On the Acoustic Characterization of Ejective Stops in Waima’a

We examine some acoustic properties of ejective stops in Waima’a (an Austronesian language spoken in East Timor), and compare them with other voiceless stop types that occur in the language. Previous studies of ejectives in other languages have suggested that they may fall into two classes, strong and weak. We compare our Waima’a results with some existing findings in the literature, and suggest that while Waima’a ejectives might appear to be more appropriately characterized as strong on some criteria, they do not sit squarely in either category

Temporal Variability and Stability in Infant-Directed Sung Speech: Evidence for Language-specific Patterns.

In this paper, sung speech is used as a methodological tool to explore temporal variability in the timing of word-internal consonants and vowels. It is hypothesized that temporal variability/stability becomes clearer under the varying rhythmical conditions induced by song. This is explored crosslinguistically in German – a language that exhibits a potential vocalic quantity distinction – and the non-quantity languages French and Russian. Songs by non-professional singers, i.e. parents that sang to their infants aged 2 to 13 months in a non-laboratory setting, were recorded and analyzed. Vowel and consonant durations at syllable contacts of trochaic word types with ¦CVCV or ¦CVːCV structure were measured under varying rhythmical conditions. Evidence is provided that in German non-professional singing, the two syllable structures can be differentiated by two distinct temporal variability patterns: vocalic variability (and consonantal stability) was found to be dominant in ¦CVːCV structures whereas consonantal variability (and vocalic stability) was characteristic for ¦CVCV structures. In French and Russian, however, only vocalic variability seemed to apply. Additionally, findings suggest that the different temporal patterns found in German were also supported by the stability pattern at the tonal level. These results point to subtle (supra) segmental timing mechanisms in sung speech that affect temporal targets according to the specific prosodic nature of the language in question

Comparison of Word Intelligibility in Spoken and Sung Phrases

Twenty listeners were exposed to spoken and sung passages in English produced by three trained vocalists. Passages included representative words extracted from a large database of vocal lyrics, including both popular and classical repertoires. Target words were set within spoken or sung carrier phrases. Sung carrier phrases were selected from classical vocal melodies. Roughly a quarter of all words sung by an unaccompanied soloist were misheard. Sung passages showed a seven-fold decrease in intelligibility compared with their spoken counterparts. The perceptual mistakes occurring with vowels replicate previous studies showing the centralization of vowels. Significant confusions are also evident for consonants, especially voiced stops and nasals

Speech intelligibility in multilingual spaces

No abstract available

A silent speech system based on permanent magnet articulography and direct synthesis

In this paper we present a silent speech interface (SSI) system aimed at restoring speech communication for individuals who have lost their voice due to laryngectomy or diseases affecting the vocal folds. In the proposed system, articulatory data captured from the lips and tongue using permanent magnet articulography (PMA) are converted into audible speech using a speaker-dependent transformation learned from simultaneous recordings of PMA and audio signals acquired before laryngectomy. The transformation is represented using a mixture of factor analysers, which is a generative model that allows us to efficiently model non-linear behaviour and perform dimensionality reduction at the same time. The learned transformation is then deployed during normal usage of the SSI to restore the acoustic speech signal associated with the captured PMA data. The proposed system is evaluated using objective quality measures and listening tests on two databases containing PMA and audio recordings for normal speakers. Results show that it is possible to reconstruct speech from articulator movements captured by an unobtrusive technique without an intermediate recognition step. The SSI is capable of producing speech of sufficient intelligibility and naturalness that the speaker is clearly identifiable, but problems remain in scaling up the process to function consistently for phonetically rich vocabularies

Spectral Characteristics of Schwa in Czech Accented English

The English central mid lax vowel (i.e., schwa) often contributes considerably to the sound differences between native and non-native speech. Many foreign speakers of English fail to reduce certain underlying vowels to schwa, which, on the suprasegmental level of description, affects the perceived rhythm of their speech. However, the problem of capturing quantitatively the differences between native and non-native schwa poses difficulties that, to this day, have been tackled only partially. We offer a technique of measurement in the acoustic domain that has not been probed properly as yet: the distribution of acoustic energy in the vowel spectrum. Our results show that spectral slope features measured in weak vowels discriminate between Czech and British speakers of English quite reliably. Moreover, the measurements of formant bandwidths turned out to be useful for the same task, albeit less direc

Tonal Activity in Kara, an Austronesian language spoken in New Britain

This paper presents the results of a small phonetic investigation of tonal activity in Kara, a little-known Austronesian language spoken in Papua New Guinea. Sketchy reports of some kind of tonal contrast in this language surfaced in the 1960s and 1970s, only to disappear in later published references to the language. Our auditory and acoustic investigations confirm the existence of contrastive tone in Kara. Native speaker intuitions also support such a conclusion. At least two tonemes (high and low) are identified. A third tone level (mid) is also noted but appears to be a variant of the low toneme