Palatal Clicks Research Articles

Opposing sound shifts involving alveolar and palatal clicks (ǃ ~ ǂ) in the ǃUi subgroup of TUU languages from southern Africa

Opposing sound shifts involving alveolar and palatal clicks (ǃ ~ ǂ) in the ǃUi subgroup of TUU languages from southern Africa

The early history of clicks in Nguni

AbstractLanguage contact between migrating Bantu speakers and resident Khoisan speakers has resulted in the adoption of clicks in various southern African Bantu languages. This paper uses the comparative method to show that for one particular cluster of Bantu click languages, the Nguni languages, a large number of phonemic clicks can be reconstructed to its putative ancestor Proto-Nguni, including a palatal click rarely found in Bantu languages and no longer used as such in any living Nguni language. Although clicks have undergone subsequent developments in individual Nguni languages, no new click phonemes were acquired through language contact, showing that clicks were already present very early in the history of the Nguni languages. This relative chronology provides new insights into how the relations between Bantu- and Khoisan-speaking communities in southern Africa developed over time.

Artificial neural network classification of foliage targets from spectrograms of sequential echoes using a biomimetic audible sonar

Classifying foliage targets using echolocation is important for recognizing landmarks by bats using ultrasonic emissions and blind human echolocators (BEs) using palatal clicks. Previous attempts to classify foliage used ultrasonic frequencies and single sensor (monaural) detection. Motivated by the echolocation capabilities of BEs, a biomimetic sonar emitting audible clicks acquired 5600 binaural echoes from five sequential emissions that probed two foliage targets at aspect angles separated by 18°. Echo spectrograms formed feature vector inputs to artificial neural networks (ANNs) for classifying two targets, Ficus benjamina and Schefflera arboricola, with leaf areas that differ by a factor of four. Classification performances of ANNs without and with hidden layers were analyzed using tenfold cross-validation. Performance improved with input feature size, with binaural echo classification outperforming that using monaural echoes for the same number of emissions and for the same number of echoes. Linear classification accuracy was comparable to that using nonlinear classification with both achieving fewer than 1% errors with binaural spectrogram features from five sequential emissions. This result was better by a factor of 20 compared to previous classification of these targets using only the time envelopes of the same echoes.

Palatal click allophony in Mangetti Dune !Xung: Implications for sound change

Click consonants are well known for lacking allophonic variation. This lack of variation has been attributed to the existence of articulatory constraints on the coronal constrictions that are imposed by the existence of a second dorsal constriction. The current study investigates temporal acoustic differences among the four contrastive coronal click types in the /i/ and /u/ contexts in Mangetti Dune !Xung. Clicks have been described as being either non-affricated or affricated. However, when vowel context is taken into consideration, the typology is more complex. The alveolar click is non-affricated in both vowel contexts. The dental and lateral clicks are fricated in both contexts. The palatal click in the /i/ context has two clear anterior and posterior transients, followed by palatal frication, while in the /u/ context it is non-affricated. Results are consistent with an analysis of the palatal click in the /i/ context as involving allophonic secondary palatalization. There are trading relations between the duration of the click burst, frication noise and aspiration noise phases. Results have implications for understanding the synchronic and diachronic phonology of click consonants.

Audible sonar images generated with proprioception for target analysis

Some blind humans have demonstrated the ability to detect and classify objects with echolocation using palatal clicks. An audible-sonar robot mimics human click emissions, binaural hearing, and head movements to extract interaural time and level differences from target echoes. Targets of various complexity are examined by transverse displacements of the sonar and by target pose rotations that model movements performed by the blind. Controlled sonar movements executed by the robot provide data that model proprioception information available to blind humans for examining targets from various aspects. The audible sonar uses this sonar location and orientation information to form two-dimensional target images that are similar to medical diagnostic ultrasound tomograms. Simple targets, such as single round and square posts, produce distinguishable and recognizable images. More complex targets configured with several simple objects generate diffraction effects and multiple reflections that produce image artifacts. The presentation illustrates the capabilities and limitations of target classification from audible sonar images.

Experimental audible sonar to model echolocation by the blind

Some blind humans echolocate by emitting palatal clicks and processing echoes, even when there is temporal emission/echo overlap (EEO). Our previous work indicates that high frequencies in the emission that travel directly to the ears are attenuated and, when high frequencies are heard, they come from target echoes. Binaural processing of these high frequency components in the EEO signals provide target range and bearing. Our experiments with 3D-printed parabolic pinnae and a speaker emitter indicate that while the high frequency components are important for object classification, the low frequencies in the emission provide more robust bearing localization because pinna diffraction effects are reduced. Classifying targets with EEO signals requires analysis in the power spectral domain because of the phase insensitivity of hearing. The power spectrum Fourier inverse estimates the autocorrelation function of the target reflector sequence. Robust autocorrelation estimates occur when the emission and echo contain comparable energies. Our experiments demonstrate that the echo energy varies with target type (e.g., planar or cylindrical) and the optimum range for classification depends on the target and itself forms a target classification feature.

Modeling human echolocation of near-range targets with an audible sonar.

Blind humans echolocate nearby targets by emitting palatal clicks and perceiving echoes that the auditory system is not able to resolve temporally. The mechanism for perceiving near-range echoes is not known. This paper models the direct mouth-to-ear signal (MES) and the echo to show that the echo enhances the high-frequency components in the composite MES/echo signal with features that allow echolocation. The mouth emission beam narrows with increasing frequency and exhibits frequency-dependent transmission notches in the backward direction toward the ears as predicted by the piston-in-sphere model. The ears positioned behind the mouth detect a MES that contains predominantly the low frequencies contained in the emission. Hence the high-frequency components in the emission that are perceived by the ears are enhanced by the echoes. A pulse/echo audible sonar verifies this model by echolocating targets from 5 cm range, where the MES and echo overlap significantly, to 55 cm. The model predicts that unambiguous ranging occurs over a limited range and that there is an optimal range that produces the highest range resolution.

Posterior lingual gestures and tongue shape in Mangetti Dune !Xung clicks

Clicks differ from pulmonic stops in that, in addition to containing lingual gestures that shape the filtering mechanism of the vocal tract, they also contain lingual “rarefaction gestures” that form the source of the lingual ingressive airstream. The current study uses mid-sagittal lingual ultrasound imaging to investigate (1) overall tongue shape, (2) tongue dorsum and root positions, and (3) dynamic rarefaction gestures involving the tongue dorsum and root, in the four coronal click types recognized by the IPA. The study provides quantitative evidence that the four click types differ in overall tongue shape. Additionally, results show that the palatal click has a farther back dorsal constriction than the three pre-palatal clicks, and the tongue root is raised and bunched in the upper pharynx in one variant of the palatal click, but involves retraction of the tongue root proper in the lower pharynx in the alveolar click. A second variant of the palatal click involves posterior gestures more similar to those found in the alveolar click. Results provide evidence that the kinematics of the posterior part of the tongue are important in describing click production, and shed light on synchronic and diachronic sound patterns involving the palatal click in Kx’a languages.

C-V coarticulation in consonants with multiple lingual constrictions

C-V coarticulation in monosyllabic words containing initial click consonants and /i:/ vowels is investigated in Mangetti Dune !Xung with 114 fps lingual ultrasound and acoustic data collected using the CHAUSA method [Miller and Finch (2011)]. The 114 fps rate yields an image of the tongue every 9 ms (+/−4.5 ms). Vowels following clicks have three lingual gestures involving the tongue tip/blade (TT), tongue body (TB), and tongue root (TR). TT and TB constrictions carried over from the clicks merge into a single vowel constriction at consonant specific rates. The second formant (F2) distinguishes each word type through the vowel midpoint. In regression analyses, TBCL and TRCL best predict F2 for alveolar click initial words, while TTCL best predicts F2 for dental/palatal click initial words. The more open constriction is acoustically inert. In the palatal click initial word, both constrictions are equally close for some speakers, and the gestures undergo blending [Browman and Goldstein (1990)]. I argue that these patterns are prosodically controlled. Dental and palatal clicks have TB and TR gestures associated with the syllable onset. In alveolar clicks, the right edge of TB and TR gestures are aligned to the right edge of the first mora.

Spectral Biomimetic Technique for Wood Classification Inspired by Human Echolocation

Palatal clicks are most interesting for human echolocation. Moreover, these sounds are suitable for other acoustic applications due to their regular mathematical properties and reproducibility. Simple and nondestructive techniques, bioinspired by synthetized pulses whose form reproduces the best features of palatal clicks, can be developed. The use of synthetic palatal pulses also allows detailed studies of the real possibilities of acoustic human echolocation without the problems associated with subjective individual differences. These techniques are being applied to the study of wood. As an example, a comparison of the performance of both natural and synthetic human echolocation to identify three different species of wood is presented. The results show that human echolocation has a vast potential.

Discovering Your Inner Bat: Echo–Acoustic Target Ranging in Humans

Echolocation is typically associated with bats and toothed whales. To date, only few studies have investigated echolocation in humans. Moreover, these experiments were conducted with real objects in real rooms; a configuration in which features of both vocal emissions and perceptual cues are difficult to analyse and control. We investigated human sonar target-ranging in virtual echo-acoustic space, using a short-latency, real-time convolution engine. Subjects produced tongue clicks, which were picked up by a headset microphone, digitally delayed, convolved with individual head-related transfer functions and played back through earphones, thus simulating a reflecting surface at a specific range in front of the subject. In an adaptive 2-AFC paradigm, we measured the perceptual sensitivity to changes of the range for reference ranges of 1.7, 3.4 or 6.8 m. In a follow-up experiment, a second simulated surface at a lateral position and a fixed range was added, expected to act either as an interfering masker or a useful reference. The psychophysical data show that the subjects were well capable to discriminate differences in the range of a frontal reflector. The range-discrimination thresholds were typically below 1 m and, for a reference range of 1.7 m, they were typically below 0.5 m. Performance improved when a second reflector was introduced at a lateral angle of 45°. A detailed analysis of the tongue clicks showed that the subjects typically produced short, broadband palatal clicks with durations between 3 and 15 ms, and sound levels between 60 and 108 dB. Typically, the tongue clicks had relatively high peak frequencies around 6 to 8 kHz. Through the combination of highly controlled psychophysical experiments in virtual space and a detailed analysis of both the subjects' performance and their emitted tongue clicks, the current experiments provide insights into both vocal motor and sensory processes recruited by humans that aim to explore their environment by echolocation.

An ultrasonographic investigation of cleft-type compensatory articulations of voiceless velar stops

Ultrasound imaging was used to investigate the articulation of the voiceless velar stop [k] in five speakers with compensatory articulation related to cleft palate. The perceptual evaluation of the acoustic realization and the visual assessment of the tongue movement for the target sound were made by three examiners. The analysis revealed a variety of different compensatory strategies that included glottal stops, pharyngeal stops, midpalatal stops and glottal and velar co-productions. One patient produced palatal click sounds together with a midpalatal stop. The ultrasound imaging also revealed covert articulatory movements that would have been missed in a purely perceptual analysis. The analysis of the ultrasound images points to subphonemic aspects of cleft-type compensatory articulation that are important to understand for speech therapy.

Physical Analysis of Several Organic Signals for Human Echolocation: Hand and Finger Produced Pulses

In the first part of this work we studied several oral signals suitable for human echolocation. Palatal clicks were proven to be optimal pulses for this task. In the second part of this series, we analyze, from a physical and psychoacoustical point of view, the sounds produced by hand clapping and finger snapping. One additional sound is studied: a loud sound made by clapping one finger against the vacuum space between fingers near the knuckles. The results of our experiments show that these sounds are fairly good for echolocation. The best one is the knuckle vacuum pulse, due to its extraordinary acoustical properties. This sound has many of the good characteristics of palatal clicks with an even richer content in the high frequency part of the spectrum. Besides, this sound exhibits an interesting symmetry in the ultrasound range, which palatal clicks do not have. Experimenters noticed that, in spite of their sound quality, hand and finger produced pulses were inferior to palatal clicks, mainly due to difficulties in the relative orientation between the head and the hands, without sight clues, lack of reproducibility and muscle fatigue during long sessions. Some people with basic echolocation skills, however, found these sounds useful for distant sources, because they were able to make such pulses louder than palatal clicks.

Clicks with noisy accompaniment in West !Xoon

The current study is concerned with ingressive stops (clicks) with a noisy accompaniment exemplified by data from West !Xoon, a Taa variety ("!Xóõ", Tuu/Southern Khoisan) spoken in Namibia. Within the obstruent system of West !Xoon, we describe (1) aspirated clicks, (2) clicks followed by a laryngeal fricative, (3) clicks with an aspirated uvular accompaniment, and (4) clicks followed by a uvular fricative. In previous analysis for the variety of East !Xoon (Traill and Ladefoged, 1994), (2) were analysed as series of "delayed aspiration", while the contrast between (1) and (3) was ignored. A novelty discovery are prenasalized "voiced" clicks followed by [h], the voiced counterparts of clicks with "delayed aspiration", which are probably absent in East !Xoon. We present an acoustic analysis of alveolar and palatal clicks based on field data of 6 speakers (3 male /3 female), where for each click type plus noise accompaniment three tokens in #CV context had been recorded repeatedly. As descriptive parameters served durational measures of burst length, cluster length, length of aspiration delay, and spectral measures of burst and friction parts. In opposite to the previous distinction our findings suggest a clear 3-way distinction of clicks (1-3) with noisy accompaniment.

Unresolved issues in the representation and phonetic description of click articulation in Xhosa and Zulu

The paper addresses three issues that are regarded as unresolved with respect to the representation and description of click sounds in Xhosa and Zulu. These issues relate to (i) different phonetic transcription systems for clicks, (ii) a controversy regarding the specification of places of articulation for clicks, and (iii) the phonetic content of socalled ‘noisy’ or affricated clicks. Current practices regarding the use of the revised IPA symbols for clicks are discussed against the backdrop of experimental phonetic results on click articulations as obtained through electropalatographic (EPG) techniques. It is argued that the use of the symbols usually used for velar stops as components of a click representation is unfounded and that it actually obscures other salient features of click articulations. A simplified system is proposed for Bantu languages such as Zulu and Xhosa. The place of articulation of palatal clicks in Zulu is confirmed through the presentation of EPG data linking it to the [!] phonetic symbol that is more generally used to denote alveolar clicks. The traditional views on the phonetic content of noisy (affricated) dental and alveo-lateral clicks are challenged in view of data obtained through an innovative speech processing technique (Smoothed Pseudo-Wigner Distribution Analysis) that combines the good frequency resolution of narrow band spectrograms and the good time resolution of wide band spectrograms. It is shown that these sounds are not affricated, but in fact pre-affricated and that traditional interpretations of waveforms are incorrect.

Release direction in clicks correlates with coarticulation patterns

Electropalatograhic data from one speaker’s productions of Khoekhoe palatal and alveolar clicks is presented. In alveolar clicks, the anterior part of the posterior constriction lowers first, increasing lingual cavity volume for rarefaction. The apical alveolar anterior constriction is abrupt. These clicks occur more frequently with [ai] than with [i]. Palatal click production exhibits apico‐laminal anterior contact from the dental to post‐alveolar regions, velar contact, and a small palatal opening. The anterior release starts with dental separation, followed by alveolar separation. Post‐alveolar contact is released last, simultaneously with velar contact forming the front edge of the posterior constriction. The palatal click anterior release is simultaneous with the posterior release, involving a larger contact area and a smaller cavity volume than the alveolar click. Anterior constriction contrasts in these clicks are apical alveolar versus laminal post‐alveolar. The post‐alveolar laminal click occurs freely with front vowels, while the apical alveolar click occurs freely with [ai], and less frequently with [i]. Anterior and posterior click releases follow the direction of airflow: Front to back. Release direction correlates with posterior constriction coarticulation patterns. [Work supported by NSF.]

Tongue dorsum location and tongue root retraction in alveolar and palatal clicks in the endangered language N/uu

Traill (1985) describes Xoo clicks as having velar posterior constriction locations (PCL). Miller et al. (to appear) show that the PCLs of Khoekhoe alveolar and palatal clicks are uvular and uvulo-pharyngeal. Ladefoged and Maddieson (1996) discuss clicks involving a uvular posterior release location (PRL) (and an implied velar PCL). An ultrasound investigation of velar and uvular pulmonic stops, alveolar and palatal velar clicks, and palatal uvular clicks, in the endangered language N/uu is presented. Results are for 15 repetitions of each consonant in the u context by four of the remaining speakers. The alveolar click has the tongue dorsum (TD) between the velar and uvular stops, and tongue root retraction (TRR) like the uvulars. The TD in the palatal click is also similar to the velar and uvular stops, but there is no TRR. The TD in the uvular palatal click is at the uvulo-phrayngeal location, and there is TRR similar to the uvular stop, in both the closure and the release. TRR in the alveolar-uvular and palatal-uvulo-pharyngeal clicks explains their phonological patterning with uvulars. The lack of TR retraction in the palatal click explains its patterning with velars. [Work supported by NSF, BCS ♯0236735.]

Clicks in a Chinese nursery rhyme

Clicks (speech sounds produced by velaric suction) have been reported in a number of African languages but have never been reported elsewhere in the world. However, several Chinese dialects have been discovered to use clicks in a special children’s version of a traditional nursery rhyme. This paper reports on the nasalized palatal clicks found in two different renditions of this nursery rhyme. The clicks replace normally occurring syllable-initial velar nasals in this special version, which apparently functions as a tongue-twister in those dialects that display this behavior. The clicks are completely integrated within the syllable structure of the words that they occur in, and sound quite similar to those found in Xhosa and !Kung. The paper will present articulatory descriptions and acoustic analyses of the clicks, and there will be an audio tape available for those who wish to hear the data. Some speculation on the origins and functions of the clicks will be presented.

'N lysie Hottentotse woorde uit 1626

SYNOPSIS Thomas Herbert, “Esquire” (later knighted) was at Table Bay in 1626 as a young man of about 21 years of age, and here he compiled a list of 31 Hottentot words, including the numeralia 1–10. This is the oldest known collection of words of this interesting click language which travellers found so very difficult to write. This article is a study of all known old glossaria of Khoi‐Khoin up to 1815. It deduces certain “consonant laws” and the author was in a position to identify with certainty 28 of the 31 words of Herbert. For this he sometimes had to re‐interpret Herbert's English, e.g. his “skin” was used for our “kaross”, his “yard” means a “kraal” or a complex of Hottentot huts, and his “egge‐shelles” is based on confusing material with the object, here a “pot” made of ostrich egg‐shells. Most astonishing and exciting was the proof that Herbert did in fact distinguish between three different click sounds and developed a way of writing them. The sharp, clear palatal and cerebral implosive clicks (...