Karen L. Landahl

Acoustic invariance and the perception of place of articulation: A selective adaptation study

Two adaptation experiments were conducted exploring the perception of place of articulation in stop consonants. We hope to determine whether in making a phonetic decision about place of articulation, the perceptual system is sensitive to subtle changes in the fine structure of a CV stimulus (i.e. onset formant frequencies and transition motions) when both the adapting and test stimuli shared the same invariant properties. These invariants are defined in terms of the gross spectral shape at stimulus onset. In the first experiment, the effects of adaptors varying in duration (full CV syllables or shortened CV syllables called onsets), vowel context ([a] versus [i]), onset formant frequencies, and presence or absence of moving transitions were tested on CV [ba da ga] test stimuli. All adaptors contained sufficient information to extract the invariant properties for place of articulation based on spectral shape at consonant release. Results showed that the various onsets did not adapt full CV [ba da ga] test stimuli. In the second experiment, the effects of the onset adaptors were tested on onset CV [ba da ga] test stimuli. Results showed that onsets can adapt an onset place of articulation continuum in a manner similar to place of articulation adaptation using full CV syllables. Further, the fine structure of the stimuli significantly affected the adaptation results. Finally, vowel contingency effects seem to reflect differences in onset frequencies of the consonants in CV syllables rather than the steady-state frequencies of the following vowels.

The b/w contrast and considerations of syllable duration

Recent research suggests that a set of acoustic properties are ambiguous with regard to their categorization as /b/ or /w/ depending on the duration of the following vowel [J. Miller and A. Liberman, Percept. Psychophys. 25, 457–465 (1979)]. Such evidence causes difficulty for a theory of acoustic invariance [S. Blumstein and K. N. Stevens, J. Acoust. Soc. Am. 66, 1001–1017 (1981)], since identification of properties at the onset appears to be dependent on the context of later‐occurring acoustic material. We repeated earlier experiments [J. Miller and A. Liberman, Percept. Psychophys. 25, 457–465 (1979)] with some variation. While maintaining continua of stimuli between /b/ and /w/, our stimuli were made more natural by manipulating the spectrum of voicing prior to consonant release. The consequence was weak prevoicing and an abrupt onset at the /b/ end, and stronger prevoicing and a gradual onset at the /w/ end. Results showed that the tendency for identification of mid‐valued stimuli to be affected by t...

Sentence intonation in British and American English

Recent theories for sentence intonation have proposed quantitative metrics for the F0 contours of sentences. Declination theories have claimed that (1) the “top line” of F0 peaks falls throughout a sentence, (2) the top line peaks at some specified time and then falls. A test of these theories is described using as a corpus the F0 contours that were published in the Lebendige Sprache monograph series between 1937 and 1940. These experimental studies derived F0 contours for speakers of British (RP) and American English reading stories, delivering political speeches, in theatrical performances, and in conversations. Neither claim (1) nor (2) is characteristic of most sentences in the corpus. Although F0 declinations occurred for some sentences for some speakers, other sentences were best characterized by relatively level F0 contours marked by F0 peaks corresponding to phonetic prominence and abrupt, sentence‐terminal F0 falls. In contrast to the claims of declination theories, F0 contours that gradually ros...

Burst spectra of word‐medial voiced stops: systematicity and variation across speakers and rates

This study extends the investigation of word‐medial stop consonants by Hemphill et al. [CLS 33(2), 333–346 (1997)]. They found that burst spectra for /d/ and /g/ for one speaker at one rate show invariant properties. In continuation of this work, linear predictive coding and spectrogram analyses were performed on stops, including /b/, in /alba/, /alda/, /alga/, /arba/, /arda/, and /arga/ spoken in a carrier sentence by two male and two female speakers of Midwestern American English across slow, normal, and fast rates. Schematic application of the criteria established by Blumstein and Stevens [J. Acoust. Soc. Am. 66, 1001–1017 (1979)] revealed characteristic spectral features for the burst of /g/ across all speakers and rates: a compact peak in midfrequency range. Spectra of the /b/ tokens displayed considerable variation, although they were generally characterizable as diffuse‐falling or flat. The /d/ tokens displayed even greater variation and failed to show diffuse‐rising or any distinctive spectral sha...

Perception of stops in naturally produced V[l/r][b/d/g]V tokens: a reassessment of acoustic cues to place of articulation

This perceptual experiment reassesses a traditional assumption that the F3 transition is the primary cue for distinguishing [da] from [ga], evidence of which comes from perceptual experiments using synthetic continua [Mann, Percept. Psychophys. 5, 407–412 (1980); Fowler et al., ibid. 48, 559–570 (1990); Liberman, Speech (1996)]. Stimuli were tokens of /alba/, /alda/, /alga/, /arba/, /arda/, /arga/ produced three times by four speakers at three rates (fast, normal, slow), analyzed acoustically by Dainora et al. [J. Acoust. Soc. Am. 100, 2601 (1996)] and Hemphill et al. [CLS 33, 333–346 (1997)]. Subjects identified tokens in their original carrier sentences using a forced choice paradigm. Stimuli were blocked by speaker and rate; three repetitions of each were randomized within blocks. In five of the 216 tokens, for one or more subjects, the percept of the stop did not match the speaker’s intent. Analysis of these tokens showed a mismatch between formant transitions and burst spectra: formant transitions we...

The supraformant hypothesis for vowels: Evidence from Norwegian

In contrast with English, examination of spectrograms of Norwegian vowels indicated that traditional formant measurements [Peterson and Barney, J. Acoust. Soc. Am. 24, 175–184 (1952)] were inadequate to characterize its nine long‐vowel categories. Given Norwegian’s distinct patterns of formant convergences and attenuations, it is hypothesized that spectral shape is better described by supraformants, second‐order acoustic structures shaped by formant structure. Supraformants quantify the continuous spectral shape into distinct peaks associated with each vowel category. Schematic supraformant patterns for Norwegian have been previously reported [J. Acoust. Soc. Am. 98, 2966 (1995)]. Here 387 tokens of Norwegian vowels from 12 native speakers were analyzed (two children, four males, six females). For each vowel token, an LPC plot of peak frequency versus bandwidth was generated with the filter‐order set intentionally low in an attempt to extract supraformants instead of formants. The resulting data set for e...

An analysis of Norwegian vowels: What determines the topography of a vowel space?

Paucity of information on the acoustic structure of Norwegian and interest in comparing similarities and differences with its well‐described neighbor, Swedish, led to an investigation of Norwegian vowels. A commutation set of single‐word utterances was presented to 12 native speakers (4 male, 6 female, 2 children), yielding a corpus of 505 tokens. Spectrographic analysis guided measurement of each vowel’s first five formant frequencies both at a single point in steady state (single FFT) and throughout (overlapping FFTs) to exploit the varying fundamental frequency through the steady state, which affords a more accurate reading of the formants. Results indicate a pattern of formant convergences and attenuations in the range of the first four formants, a robust finding which falls between the cracks when using a standard F1/F2 technique for laying out vowel spaces. That such patterns characterize different vowel categories and dimensions (front–back, rounded–unrounded) opens discussion to more general quest...

Perceptual identification of ambiguous consonant onsets

Theories of acoustic invariance propose that stop consonant place identification can be made independently of full consonant‐transition information. Consonant and vowel identification is possible within a few milliseconds of stop release, although the distribution of the acoustic energy in the consonant onset spectrum is frequently inconsistent with the distribution for the following vowel. The presence of oral physiologic impairment may be expected to influence whatever consonant‐vowel interaction may contribute to syllable perception. The purpose of this study was to examine consonant/vowel identification for two glossectomee speakers and one normal control. For the most impaired speaker, removal of poorly identified vowel information enhanced consonant identification. For the normal speaker and the less impaired speaker, full CVs were well identified. Removal of vowel information diminished correct consonant identification for the glossectomee speaker but for the normal speaker affected only those cons...

Perceptual categorization of a compressed vowel space

Acoustic properties of vowel tokens produced by a speaker with radical malformation of the vocal tract have been investigated. A study of vowel formant structures demonstrated that the speaker does not maintain expected intravowel formant relationships which results in a diminished vowel space. However, the speakerapos;s vowel categories do display formant structures which are patterned after the norm [Peterson‐Falzone and Landahl, Speech and Language (Academic, New York, 1981), Vol. 6]. The question remains in what way the anomalous formant structures will affect vowel categorization by listeners. A previous report of modeled speech [Landahl and Gould, J. Acoust. Soc. Am. Suppl. 1 77, S100 (1985)] suggests that this speakers perceived vowel space will not include vowel categories at the periphery. The current study reports perceptual testing of vowel tokens produced by this speaker. The results of these tests concerning the existence of peripheral vowels are in accord with earlier predictions that the s...

Anchor line theory of fundamental frequency variation in speech

We propose a theory that appears to characterize quantitatively those aspects of the temporal pattern of fundamental frequency (F0) variation that delimits the constituent structure of speech, most notably sentences. The anchor line frequency theory we propose provides a major refinement of the breath‐group theory [P. Lieberman, Intonation, Perception and Language (MIT Press, Cambridge, MA, 1967); J. E. Atkinson, J. Acoust. Soc. Am. 63, 211–222 (1978)]. We will present an analysis of data that is consistent with the hypothesis that the F0 contour (1) provides continuity across voiced‐unvoiced segmental boundaries, (2) that local F0 minima tend to fall on anchor lines, (3) that the anchor lines are linear level, falling, or rising, and (4) that the level anchor is most characteristic for normal, nonemphatic declarative sentences of American English and English. We further propose that the F0 continuity inherent in the anchor lines may play a crucial function in the perception of speech by “tagging” a speak...