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Anatomy of speech

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Anatomy of speech

Spoken language relies on human physical ability to produce sound, which is a longitudinal wave propagated through the air at a frequency capable of vibrating the ear drum. This ability depends on the physiology of the human speech organs. These organs consist of the lungs, the voice box (larynx), and the upper vocal tract – the throat, the mouth, and the nose. By controlling the

different parts of the speech apparatus, the airstream can be manipulated to produce different speech sounds.

The sound of speech can be analyzed into a combination of segmental and suprasegmental elements. The segmental elements are those that follow each other in sequences, which are usually represented by distinct letters in alphabetic scripts, such as the Roman script. In free flowing speech, there are no clear boundaries between one segment and the next, nor usually are there any audible pauses between words. Segments therefore are distinguished by their

distinct sounds which are a result of their different articulations, and they can be either vowels or consonants. Suprasegmental phenomena encompass such elements as stress, phonation type, voice timbre, and prosody or intonation, all of which may have effects across multiple segments

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Anatomy of speech

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Anatomy of speech

Consonants and vowel segments combine to form syllables, which in turn combine to form utterances; these can be distinguished phonetically as the space between two inhalations.

Acoustically, these different segments are characterized by different formant structures, that are visible in a spectrogram of the recorded sound wave (See illustration of Spectrogram of the

formant structures of three English vowels). Formants are the amplitude peaks in the frequency spectrum of a specific sound.[60][61]

Vowels are those sounds that have no audible friction caused by the narrowing or obstruction of some part of the upper vocal tract. They vary in quality according to the degree of lip aperture and the placement of the tongue within the oral cavity.[60] Vowels are called close when the lips are

relatively closed, as in the pronunciation of the vowel [i] (English "ee"), or open when the lips are relatively open, as in the vowel [a] (English "ah"). If the tongue is located towards the back of the mouth, the quality changes, creating vowels such as [u] (English "oo"). The quality also changes depending on whether the lips are rounded as opposed to unrounded, creating distinctions such as that between [i] (unrounded front vowel such as English "ee") and [y] (rounded front vowel such as German "ü").[

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Anatomy of speech

Consonants are those sounds that have audible friction or closure at some point within the upper vocal tract. Consonant sounds vary by place of articulation, i.e.

the place in the vocal tract where the airflow is obstructed, commonly at the lips, teeth, alveolar ridge, palate, velum, uvula, or glottis. Each place of

articulation produces a different set of consonant sounds, which are further distinguished by manner of articulation, or the kind of friction, whether full closure, in which case the consonant is called occlusive or stop, or different

degrees of aperture creating fricatives and approximants. Consonants can also be either voiced or unvoiced, depending on whether the vocal cords are set in vibration by airflow during the production of the sound. Voicing is what

separates English [s] in bus (unvoiced sibilant) from [z] in buzz (voiced sibilant)

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Anatomy of speech

Some speech sounds, both vowels and consonants, involve release of air flow through the nasal cavity, and these are called nasals or nasalized sounds. Other sounds are defined by the way the tongue moves within the mouth: such as the l- sounds (called laterals, because the air flows along both sides of the tongue), and the r-sounds (called rhotics) that are characterized by how the tongue is positioned relative to the air stream.

By using these speech organs, humans can produce hundreds of distinct sounds:

some appear very often in the world's languages, whereas others are much more common in certain language families, language areas, or even specific to a single language.

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Anatomy of speech

When we exhale, air travels from the lungs up into the trachea. The first place where we can start messing with the air stream is the larynx,

which is perched at the top of the trachea. We can contract muscles in

the larynx to manipulate bands of tissue called the vocal cords (or vocal

folds). The vibration of the vocal cords is called phonation.

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Anatomy of speech

By regulating the tension of the vocal cords and changing the amount of space

between them (the glottis), we can modulate the pitch, volume, and tonal quality of our voices. There is a continuum of phonation types, from whispering to “creaky

voice” (similar to vocal fry).

We can also completely stop the stream of air by fully closing the distance between the vocal folds. This gives us the glottal stop (think of the sound you make between the syllables of “uh-oh”).

Next, let’s talk about the tongue. The tongue is made up of four intrinsic muscles:

the superior lingualis, inferior lingualis, vertical lingualis, and transverse lingualis.

There are also four extrinsic tongue muscles that help the tongue move: the genioglossus, hyoglossus, palatoglossus, and styloglossus.

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Anatomy of speech

Muscle Function

Genioglossus Depresses and extends the tongue

Hyoglossus Depresses the tongue

Palatoglossus Elevates posterior tongue and constricts the pharynx

Styloglossus Draws the sides of the tongue upward and draws the

tongue back

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Anatomy of speech

It’s no wonder that the tongue has so many muscles helping it out—it needs to be pretty versatile to make the specific movements required for speech! Movements of the mouth, face, tongue, and larynx are so important, in fact, that a large portion of the primary motor cortex is devoted to them.

You might recognize the image below (the motor homunculus) from the neuromuscular interaction article from a few weeks back. The

face/tongue/larynx and hands are depicted as the largest parts of the

body in the homunculus representation because of the large regions of

motor cortex devoted to their intricate motions.

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Speech Sounds: Let's Make Some Noise!

Now we’re going to put all the muscle-y stuff together with some linguistics to give a more complete picture of how the motions of your articulators create particular sounds.

Phoneticians (linguists who study the articulatory and/or acoustic properties of speech sounds) have grouped the speech sounds humans make into several categories. There are vowels and consonants, of course, but there are also lots of smaller distinctions within those categories.

Let’s start with vowels. Vowels don’t involve stopping the stream of air as it travels up from the lungs, but they do involve changing the shape and size of the space through which the air passes. The vocal cords must also be vibrating in order for a vowel sound to be produced. If you’re an English speaker, try going through the vowel sounds “ah”

“ey” “ee” “oh” and “ooh” and pay attention to how the shape of your lips and the

amount of space inside your mouth changes. Vowel sounds can also combine to form diphthongs.

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Speech sounds

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Linguists typically group vowels based on their tongue height (high, mid, low), tension (tense, lax), and tongue position (front, central, back) as well as whether the lips are rounded.

In contrast, a consonant is basically any sound that isn’t a vowel. They involve stopping the flow of air, either fully or partially, and releasing it again. Consonants are categorized by their place and manner of articulation.

The place of articulation refers to the point at which the airflow is impeded. This can occur at the lips, teeth, alveolar ridge, hard palate, soft palate, uvula, oropharyngeal wall, epiglottis, and glottis. Much of the time, the tongue is responsible for blocking the air stream, but glottal, epiglottal, bilabial (lips are pressed together), and labiodental (top teeth press against bottom lip) sounds are notable exceptions to this generalization.

The manner of articulation refers to what happens to the air. Stop consonants (p, b, t, d, k, hard g) completely obstruct the flow of air before releasing it again. Fricatives (like s or f) create a narrow space for air to pass through, giving them a hissing sound. Affricates (ch, j) are roughly between a stop and a fricative. Approximants (r, l, w, y) involve articulators coming close enough together to qualify as a consonant rather than a vowel, but no friction is created.

Nasal sounds (like English n, m, and ng) are not your average consonants. Basically, airflow is blocked in the mouth, as in a stop consonant, but the air is allowed to flow out through the nasal cavity because the velum (soft palate) is lowered.

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Pathologies

When we string sounds and syllables into words and phrases, the primary motor cortex works together with regions of the brain, such as Broca’s area (BA 44–45), that deal with computational aspects of language production. Damage to Broca’s area results in expressive aphasia (Broca’s aphasia), which is characterized by patients having difficulty producing fluent speech, especially when complex grammar is required.

There are also a number of pathologies that can affect the articulatory/neuromuscular component of speech production.

One of these is dysarthria, in which neurological damage from stroke, traumatic brain injury, or degenerative disorders (ALS, MS, Dementia) makes it difficult to move the muscles that produce speech sounds. This is due to a disruption in the

transmission of motor signals from the brain to the articulators. Direct damage to the speech organs can result in a condition called peripheral dysarthria. Typical symptoms of dysarthria include speech that is too fast or slow, slurred, or mumbled.

People with dysarthria may also have trouble moving their jaw, tongue, or lips.

Another condition affecting speech articulation is a developmental disorder called childhood apraxia of speech (CAS).

Potential causes for CAS can include (but are not limited to) brain damage or underlying genetic conditions. Unlike dysarthria, CAS does not involve muscle weakness. Children with CAS do still have trouble moving their muscles to make speech sounds, but this problem lies more with motor planning than disruptions in the transmission of signals from brain to muscle.

Whew! That was a lot of sounds. And just think—every time you speak, your brain and muscles coordinate the required movements at lightning speed! What’s more, the sounds of English are only a piece of the full sound inventory of the world’s languages. Check out UCLA’s phonetics archive to learn more (you can listen to just about any type of speech sound on this site—it’s awesome!).

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Kaynakça

• https://en.wikipedia.org/wiki/Language

• Scovel, Thomas, 1998, Psycholinguistics, Oxford University Press.

• Cairns, Helen Smith, 1999, Psycholinguistics, Pro-Ed.

• https://

www.visiblebody.com/blog/something-to-talk-about-anatomy-of-spe

ech-sounds

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