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Module 5: Phonation and Oro-nasal Processes

Objectives:

• To look at the physiological structures and functions of the larynx and the velum in relation to speech sounds

• To help students get practice in the articulation of the sounds produced by these organs of the vocal tract

Contents:

5.1 Introduction

5.2 Phonation Process

5.2.1 The larynx

5.2.2 States of the glottis and Phonation Types

5.2.3 Practice exercises

5.3 Oro-nasal Process

5.3.1 The Velum

5.3.2 Oral sounds, Nasal consonants and Nasalized sounds

5.4 Summary

Subject name: Linguistics

Paper number & name:

2; Introduction to Phonetics & Phonology

Paper Coordinator name & contact:

Pramod Pandey Centre for Linguistics, SLL&CS, Jawaharlal Nehru University, New Delhi-110067

Module id Lings_P2_M5

Module name Phonation and Oro-nasal Processes

Content Writer (CW) Name

Pramod Pandey

Email id pkspandey@yahoo.com

Phone 011-26741258, -9810979446

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5.1 Introduction

In the present module, we discuss the following two processes of speech- the phonation process and the oro-nasal process. The phonation process deals with the various types of sounds that are produced with vocal cords held in different positions. We will see how the phonation process is dependent on the structure of the larynx. The oro-nasal process makes available the options for letting the air escape from the two cavities- the oral cavity and the nasal cavity and thereby for the production of three different types of sounds.

5.2 The Phonation Process

Once the air-stream process, which we dealt with in Module 4, is set in motion, the phonation process, dependent on the larynx, takes over.

5.2.1 The larynx

The larynx is placed in the neck, below the pharynx and the oral and the nasal cavities. Evolutionary biologists (see e.g. Lieberman & Crelin 1971, Fitch 2002) tell us that in the evolution of humans from chimpanzees and apes, there was a crucial development in the positioning of the larynx: it got lowered, adding a vertical tube in the human vocal tract. According to Fitch (2002), “…the two-tube vocal tract allows us to produce wider range of vowels, and probably other speech sounds, than would a single-tube tract.” For a difference in the structures of humans and chimpanzees, see figure 5-1 below.

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Figure 5-1: The larynx in humans and chimpanzees

Downloaded from: http://users.ugent.be/~mvaneech/Verhaegen%20&Munro.%202004.%20Speech.%20Human%20Evolution%2019,%2053-70_files/image004.jpg

The location of the larynx leads to three important functions it performs: it controls the breath flow, protects the windpipe and regulates the production of speech sounds. The central organ of the larynx is the vocal folds, which perform all the three functions. The vocal folds are “… made of muscles covered by a thin layer called mucosa. There is a right and left fold, forming a "V" when viewed from above. At the rear portion of each vocal fold is a small structure made of cartilage called the arytenoid. Many small muscles, described below, are attached to the arytenoids. These muscles pull the arytenoids apart from each other during breathing, thereby opening the airway. During speech the arytenoids and therefore the vocal folds are brought close together. As the air passes by the vocal folds in this position, they open and close very quickly. The rapid pulsation of air passing through the vocal folds produces a sound that is then modified by the remainder of the vocal tract to produce speech.” Take a look at closed and open the vocal cords in Figure 5-2.

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Figure 5-2: Closed and open vocal cords

Downloaded from:

http://img.webmd.com/dtmcms/live/webmd/consumer_assets/site_images/media/medical/hw/h9991587_001.jpg

The moving vocal folds can be viewed in the following edited video of laryngeal stroboscopy (source: https://www.youtube.com/watch?v=mJedwz_r2Pc):

LaryngealStroboscopy edited.ogg

Some of the shapes that the glottis takes can be seen in Figure 5-4.

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Figure 5-4: some shapes of the glottis during speech

Downloaded from: https://encrypted-tbn1.gstatic.com/images?q=tbn:ANd9GcS9WOSMIG8a54vs0aacSekkNKyxaTJIqosHI57X1GE_xP-JPgi5

There are two types of muscles and cartilages that control the movement of the larynx, one, broadly known as the intrinsic muscles and cartilages, lead to the horizontal contraction and expansion of the vocal folds, and the other, known as extrinsic muscles or straps, control the movement of the larynx up and down. The vertical movement of the larynx is responsible for many features of speech sounds, especially voice quality and certain types of sounds such as implosives and ejectives, discussed in Module 4. The horizontal movement of the vocal folds controls the different shapes of the vocal folds giving rise to different phonation types. The shapes of the vocal folds are also referred to as ‘glottis’, the opening between the vocal folds. The horizontal shape of the vocal folds looks as shown in Figure 5-3. There are two main muscles- the thyroarytenoid muscle and the interaretenoid muscle that move back and forth or sideways. The muscles are attached to the arytenoids cartilage that can contract and expand. The two muscles and the cartilage are shown in Figure 5-3. The opening between the arytenoids is known as the ‘glottis’.

Figure5-3: Intrinsic muscles and cartilage around the vocal fold

https://www.evms.edu/patient_care/services/otolaryngology_ent/patient_education/voice__swallowing/anatomy/

5.2.2 States of the glottis and Phonation Types

We should keep in mind the fact that the different types of phonation depend on factors such as the force of the airflow and vibration of the vocal folds as much the settings of the vocal fold or the glottis. The most important phonation types found to contrast sounds in world languages are the following: Glottal stop, Voiceless sounds, Whisper, Voiced sounds, Breathy voice or Murmur and Creaky or laryngealized sounds.

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These are described below.

A Glottal stop, symbolized as [ʔ], is produced with the vocal folds tightly closed. As the vocal folds are tightly closed, air coming from the lungs cannot escape through them during the closure period. When the vocal folds are released, an audible plosion can be heard. Although called stops, glottal stops lack many of the features of stops- they cannot be voiced or aspirated. Since the place of the glottal stops is the vocal cords themselves, any modification in the state of the glottis will not yield a stop.

Voiceless sounds are produced with the vocal folds held wide apart so that the air from the lungs passes freely through them, as in breathing. Although the most common voiceless sounds are found among obstruents, that is, plosives, fricatives and affricates, sonorants (e.g. laterals and nasals), too, can be voiceless. The voiceless obstruents are assigned independent symbols alongside their voiced counterparts, and they are placed on the left in a slot on e IPA chart, as, for example, [p b], [s z] or [ʧ ʤ]. For voiceless sonorants, a subscript diacritic, an empty dot [],isoftenused,forexample,[n], a voiceless alveolar nasal. Some of the sonorants, of course, also have independent symbols, e.g. [ ɬ ], a voiceless lateral fricative, as compared to [ɮ], a voiced alveolar lateral fricative.

Beginners in phonetics usually find it difficult to tell a voiceless from a voiced plosive, mainly on account of the fact that when voiceless plosives are released, they come together for the articulation of the following vowel, which is voiced. The release of plosives is always heard as voiced.

Voiced sounds are produced with vocal folds held loosely together with the help of the arytenoids cartilages, unlike for glottal stops, for which they are held tightly closer. As they are loosely closed, the air-stream passing through them causes them to vibrate by means of the Bernauilli Principle. According to this principle, as the air passes out with force through the vocal folds, the pressure drops. As the air pressure drops, the vocal cords come together again, to be forced again to open. The cycle produces the effect of voicing, a buzzing sound. You can feel the difference between a voiced sound and a voiceless sound by putting your fingers on the outer projection of the vocal folds on the middle front portion of the neck, known as the Adam ’s apple. Say the sounds [s] and [z] over a prolonged period for 5-10 seconds, and you will feel the buzzing sound for the prolonged [z], but not for the prolonged [s].

Aspirated sounds are found for stops for the most part, as e.g. [pʰ kʰ ʧʰ]. Aspirated sounds are produced by the vocal folds held in the position for voiceless sounds, with the difference that for aspiration, the vocal folds do not come together immediately after the release, but continue to be held apart leaving the glottis open for a short period, allowing extra force of air to pass through them.

The distinction between voiceless, voiced and aspirated sounds is conveniently measured in terms of the parameter of Voice Onset Time (a.k.a. VOT). VOT quantifies the interval

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between the release of constriction of a consonant and the onset of voicing. For voiced sounds, VOT begins before the end of the consonantal constriction, for voiceless consonants it is more or less simultaneous with the end of the constriction, and for aspirated consonants, voicing begins even after the end of the consonantal constriction. Figure Figure 5-5 shows the difference between bilabial plosives with the three laryngeal states:

Figure 5-5: VOT for voiceless unaspirated, voiceless aspirated and voiced plosives

Downloaded from: http://www.indiana.edu/~hlw/PhonUnits/vot.gif

The glottis may be partially open or partially closed to produce other types of sounds. Thus,

creaky sounds are produced by holding the anterior part slightly open or loosely together

and the posterior part tightly closed. Creaky sounds are symbolized with a subscript tilde [

],e.g.[a ]. . Creaky sounds are easy to produce non-linguistically, for example, when

in pain. Linguistically, they are found in some tonal languages, such as Thai: /kʰaiL/

[kʰai L] ‘egg’,/mail/[mai] ‘new, modern, fresh’, /kʰaoL/, [kʰaoL] ‘knee’.

Whisper is produced with the opposite configuration of the glottis: The posterior is slightly open and a high airflow is allowed to pass through this opening. The airflow is strong enough to create various resonances in the vocal tract. Whisper is difficult to produce because of the necessity of high airflow. It is often heard to be used non-linguistically, for example, for speaking secretly to someone. Linguistically, it may be produced in given contexts in some languages, such as Japanese. It is symbolized with a sub-script dot [ ], e.g. [ i ]. The diacritic was earlier used for retroflex consonants, but now it is mainly used for whisper

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and also sometimes for retroflex consonants with a relatively weak degree of retroflexion, as in Bengali or Hindi, compared to Tamil or Telugu, in which the retroflexion is relatively strong.

Breathy sounds or murmur are produced with the vocal folds brought in close proximity to each other, but never closed, as a result of which they vibrate along with extra breath force passing through them. They are symbolized with two dots as sub-scripts, as in [ a ] and [ b ]. Breathy sounds or murmur are common in a majority of Indi-Aryan languages, such as Gujarati. Colloquial Gujarati pronunciation of the word [bʱa: rət] ‘India’ in some regions has the first voiced plosive and the following vowel pronounced as strongly breathy [ba rət]. Voiced aspirates are in general assumed to be indistinguishable from breathy voiced. However, the two types of sounds sometimes need to be distinguished, as in Gujarati dialects. Standard Gujarati pronunciation of the same word is [bʱarət]. The first consonant can be said to be a voiced aspirate in Standard Gujarati, but a murmur in colloquial Gujarati.

5.3.5 Other aspects of speech dependent on the glottis

It is not only the types of speech sounds that depend on the glottis, but other aspects of speech, too. For example, the loudness of speech sounds is increased by manipulating the larynx in three ways- by opening the vocal folds further apart than for normal voice, by pushing more breath force through it, and/or by letting the vocal folds come together and separate with greater vigour. All these possibilities are available because of the highly elastic nature of the larynx and the vocal folds.

The search for a minimal set of distinctive features (see Module 25 for a detailed discussion of the topic) has led to positing spread glottis as a feature that distinguishes aspirated consonants from unaspirated consonants. However, it is not certain if other voiceless consonants are also not produced with spread glottis, such as the fricative [s] or [f]. Thus it is not merely the spread glottis but the extra breath-force that may crucially characterize aspirated consonants. More needs to be known about the interaction of the glottis with air-flow and the strength of the movement of the vocal folds.

Recall that the pitch of voice is crucially dependent on the rate of the vibration of the vocal cords- the higher the rate the higher the pitch level. In tonal languages, it is quite likely that the difference between lexical tones involves an association between the rate of vibration and the movement and the tension of the laryngeal muscles. It is the elasticity of the larynx that is expected to yield various differences among speech sounds, and that needs close investigation.

5.3.6 Practice exercises

It is now time for us to practice the different types of sounds found in world languages. Very useful materials are available on the following link:

http://www.phonetics.ucla.edu/index/sounds.html

This is a very useful link for different types of speech sounds found in world languages.

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5.4 Oro-nasal Process

The third process in the production of speech is known as the Oro-nasal process. The main articulators involved in speech production are the oral tract, the nasal tract and the upper portion of the pharynx, the nasopharyngeal port. These vary in shapes and sizes among individuals, giving rise to variation in the resonant qualities of sounds produced by individuals.

5.4.1 Oral sounds, Nasal consonants and Nasalized sounds

The three main types of sounds that are produced by the oro-nasal process are oral sounds, nasal consonants and nasal vowels. The velum plays a crucial role here. By being elastic, it can move up or down.

As the air passes from the larynx and reaches the upper part of the pharynx, there are two options available to the speaker. One is to raise or lower the velum to block one of the two tracts. When the velum is raised to block the nasal cavity the air passes out only through the oral tract. The sounds thus produced are oral sounds. All consonants except nasal consonants are oral, and all languages have oral vowels. When the velum is lowered to block the oral tract the air passes through only the nasal tract. The sounds thus produced are nasal consonants. The two types of articulation are shown in Figure 5-6.

Figure 5-6: Oral and nasal articulations

Downloaded from: http://www.ling.upenn.edu/courses/Fall_2013/ling520/oronasal.png

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The second option is for the velum to be held in a neutral position, allowing the air to pass through both the oral and the nasal tracts. The sounds thus produced are nasal vowels. Nasalvowels,ashasbeennotedbefore,aresymbolizedwithatildeasasuperscript,e.g.[a ]. It is sometimes useful to distinguish between nasal vowels and nasalized vowels. Nasal vowelsarecontrastiveinalanguage.LanguagessuchasBengali,Hindi,Punjabihavebothoralandnasalvowelsascontrastive,asforexample,[sa:s]‘mother-in-law’and[sa:s] ‘breath’ in Hindi. Nasalized vowels do not contrast but are found in the context of a neighboring nasal consonant. For example, in English the word name and miss are pronounced as [neɪm] and [mɪs]. As most languages have a nasal consonant, most languages have nasalized vowels. In some languages, even approximants such as [w] and [j] can be nasalized, as in Malay, in which if thereisanasalconsonantinawordthenthevowelsandtheapproximantsadjacenttoitarenasalized,e.g.[mewah]. Nasalized approximants are also found in Hindi, e.g. [səȷȷəm] ‘patience’, [ʧʰa:w] ‘ shade’.

5.5 Summary

In the present module, we have tried to introduce the variety of speech sounds that are produced by two speech processes- the phonation process and the oro-nasal process. The types of sounds produced by the oro-nasal process are restricted in number, whereas the types of sounds produced by the phonation process make a variety. We tried to see how the phonation process is a complex one, that is dependent on multiple factors, such as the states of the glottis, the airflow and the movement of the larynx. For a full understanding of the various features of articulation, including, suprasegmental phenomena such as stress and tone, it is necessary to inquire into the phonation process. As this is an introductory course in phonetics and phonology, we have taken into account only the main types of sounds produced by the phonation process.

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