THE ARABIC PHARYNGEAL APPROXIMANT Ashraf Alkhairy MIT Room 36-547, 50 VasserStreet, Cambridge, MA 02139, USA ABSTRACT is stochastic, comprising of both deterministic and pseudo- random components. The acousticproperties of the Arabic pharyngeal approximant in In addition to the study of the nature of the sound, a intervocallic sequences are studied. This sound has traditionally comprehensive acoustic analysis is conducted. The analysis is been classified as a voiced fricative, but our researchindicates directed towards investigation of acoustic variables that aid in that it is an approximant, with no IPA symbol. The attenuationin articulator-y and voice source modeling of the pharyngeal the intensity of the consonant from the neighboring vowels is approximant, as well as in determining acoustic cuesfor their around 11 dB, and the fundamental frequency of the consonantis perception. less than that of the vowels by 25 Hz. Study of the formant This paper is divided into six sections.Section 2 discusses trajectories indicates that Fl increasesand F3 decreasesinto the the speech samples that were used for analysis. Section 3 consonant for all contexts. The bandwidths remain unchanged investigates the nature of the sound. Section 4 studies the from that of vowels, except in the context of /a/ for which both formants. Section 5 presents results related to the glottal B2 and B3 increase.Examination of the estimatedglottal volume characteristics. Section 6 concludes the paper and provides velocity indicates an open quotient of lOO%,and a spectraltilt suggestionsfor future research. that is highly dependenton the context with an averageof 36 dB, and a value of 2%dB for the context of /a/. 2. EXPERIMENTS The Modem Standard Arabic (MSA) was used to conduct our 1. INTRODUCTION study. MSA is employed by the entire Arab population for The Arabic language consists of a relatively large number of purposes of official communication, teaching, and literature. The consonants produced with constriction in the uvular and speakers consisted of three educated adult male Saudi natives, pharyngeal regions, in addition to locations in the oral cavity with no speech or hearing impairments, and without phonetic between the velum and the lips. The articulation and training. Speech sampleswere recorded in a sound-treatedroom characteristics of the pharyngeal consonants is still not clearly into a digital computer with sampling rate of 1OkHz. understood because of lack of research, and the difficulty of The linguistic material for the experimentswere of the form measurements for these regions. These consonants involve IZNCVIZI, where C represents the approximant, and V denotes articulation of the tongue root, back wall of the pharynx, and the vowels. The approximant was in geminate form to allow possibly the epiglottis and other structures in the lower vocal more accuratemeasurements, and the vowels consistedof /a/, /u/, tract [1,2]. and Ii/. The VCV sequence were embedded within /z/ to Traditionally, Arabic has been considered to have two provide the most natural context. In a number of cases the pharyngeal consonants, a voiced and a voiceless fricative properties of the consonant are comparedto that of the vowels. [ 1,2,3,4]. The “voiced fricative” has also been classified as a To accomplish this, reference utterances consisting of /z/V/z/ voiceless stop, voiced glide, and an approximant [ 1,2,3,4,5,6,71. were also recorded,where V representsthe vowels in long form. While these discrepancies in categorization of the voiced The long versions provide better circumstancesfor the study of fricative may be attributed to differences in dialect or context, we the vowel steady state characteristics. believe that this not to be the case.Existing studieshave relied on X-ray images, and spectrographic plots to reach their 3. THE NATURE OF THE SOUND conclusions.In all cases,the images are not clear enough to make A number of analysis methods were used to determine the distinctions as far as mannersof articulation are concerned,and classification of the consonant under consideration.Both time- the plots are not of adequate resolution to make appropriate domain and frequency-domain analysis results indicate that the judgements. In this paper we make a detailed study of the nature sound is produced without the generation of any turbulence noise of the consonant and conclude that it is indeed an approximant, and without nasalization; and hence should be classified as an and a new IPA symbol is required. approximant - with a new IPA symbol. The analysismethods Classification of a sound, as far as manner of articulation is used are pressure waveform examination, intensity analysis, concerned is important in its acoustic analysis, as well as spectrogram,and spectrum. modeling, synthesis, and the determination of perceptualcues. An approximant is produced with two articulators close to one 3.1. The Pressure Waveform another, but without a narrow enough constriction to generate A first indicator of the nature of the sound, although turbulence. In contrast,the areaand shapeof the cavity between inconclusive, is obtained from visual inspection of the the two constricting articulators in a fricative are such as to waveforms in the time-domain. An example is shown in Figure 1 produce turbulent airflow. In the first case,the acoustic signal is (Top). The plot is free from random noise and is representativeof deterministic, whereas in the secondcase the pressurewaveform all the waveforms. page 1029 ICPhS99 San Francisco hcsgmi fcsgmu r I I I 4 3.5 53 1 I 3 100 150 B Time (msec) u” 2.5 s z- E 2 IL 1.5 1 0.5 -2 ’ I I I I I n 0 50 100 150 2al 250 * 250 300 350 400 450 500 Time (msec) Time (msec) Figure 1: Top: The pressurewaveform of the consonantin the Figure2: Spectrogramof the consonantin the contextof/u/. contextof/i/. Bottom: The bandpassfiltered waveform. Absence of turbulence noise in the consonantcan be fcsgmu comirmed by inspection of the bandpassfiltered waveforms centeredon the third formant, with a bandwidthof 600 Hz [S]. This methodologywas appliedto the waveformsfor all speakers and contexts. The resulting filtered signals consistof damped sinusoidssynchronized with the original waveforms;a typical example of which is shownin Figure 1 (Bottom). We thus infer rz- 0 ----- ;-- --; ---- ;- that the soundis an approximantrather than a voicedfricative. I I I 4i , I I g I I -----(---I *----q- I g -10 - v I I I 3.2. Intensity Analysis 4 I I I I I I I I I An approximantis likely to havehigher energyin comparisonto I I I -20 - ----4------c----*- 0 I 0 I I I voiced fricatives becausethe constrictionin the vocal tract for an I I I I I I approximantis less obstructive. Although voicedfricatives are 30 - ----g-----c----*-, : 1 I I I I I I i I generally attenuatedby 20 dB, no exactranges are known for I I I I I 0 I I Y 1 I I I I I I I I I I I I I I I I I I approximants and voiced fricatives. To examine intensity -40 I , I I , I 1 , 1 0 500 loo0 1500 2000 2500 3000 3500 4000 45llo 5000 characteristicsof our approximant, differences in intensity Frequency (Hz) betweenthe steady state values of the approximantand that of Figure 3: Widebandspectrum of the consonantwithin M. the following vowels were computed. The meanvalues are as follows : /a/ context(12 dB), /u/ context(14 dB), /i/ context(11 dB), and overall average(12 dB). These results support the . observationthat the consonantis an approximant. hcsgma 30 I II 1 I I I I I I I I I I I I I I I I I I I I I , I I I , I 3.3. The Spectrogram 20 --+- ----q------ I I I I I I To study the global characteristicsof the approximant,digital I I 10 -,I ----- I ------ I I spectrogramsof the utteranceswere computedusing a Hanning I I I I , I window of length 7.97 ms, an overlap of 97%, lengthof 5 12 -- f - - - - + - - - -- I I points, bandwidth of 180 Hz, and no pre-emphasis.A I I I I representativeexample is displayedin Figure2. The spectrogram 0 I has regular striations and is not diffused, indicatingcontinuous voicing andlack of turbulencenoise. -30 3.4. The Spectrum Widebandspectra at the steadystate positions of the approximant -40 -----j -----; ---- 4 ----;---l-: ---- 4 -----; ----: -----; ----- I I I I I I I I I I I I I I I I were computedusing a Hanningwindow of size 6.4 ms with no I I I I I I I I I I I I I I I I I I I I , I 1 , 1 I I -50 pre-emphasisto determinethe generalspectral characteristics of 0 500 1000 1500 Moo 2500 3000 3500 4000 4500 5000 the approximant.As the representativeexample plotted in Figure Frequency (Hz) 3 indicates, the energy is clusteredin the mid-frequencyrange, Figure4: Narrowbandspectrum of the consonantwithin /a/. andno signsof anti-resonanceare present. page 1030 ICPhS99 San Francisco To examine aspects related to the duty-cycle of the glottal The data in Table 1 clearly indicatesthat the first formant of source from the spectrum, narrowband spectrawere computed the approximantis larger than that of all the vowels, and that the with a Hanning window of size 25.6 ms. As the illustrative third formant is smaller. This is in agreement with modeling example in Figure 4 indicates, the first harmonic has a large results [6]. In the context of/i/, however, the secondformant is amplitude, implying a high open quotient. This is examinedin smaller. Further research in acoustic phonetics is required to greaterdetail in a latter section. explain the result. Bandwidth values for the approximantin the context of /a/ 4. THE FORMANTS indicate a widening of the second and third formants when The primary parametric identifier of a phoneme are formant compared to that of the adjacentvowels.