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Bilabial

What do the sounds at the beginning of pat, bat, and mat have in common? They are all produced with closed lips. Sounds that involve the lips are called bilabial sounds. There are ten distinct bilabial consonants in the International Phonetic Alphabet (IPA). These include bilabial plosives, fricatives, trills, and others. The different manners of articulation present in the bilabial consonant category allow for this single place of articulation to define differences in meaning.

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Bilabial

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What do the sounds at the beginning of pat, bat, and mat have in common? They are all produced with closed lips. Sounds that involve the lips are called bilabial sounds. There are ten distinct bilabial consonants in the International Phonetic Alphabet (IPA). These include bilabial plosives, fricatives, trills, and others. The different manners of articulation present in the bilabial consonant category allow for this single place of articulation to define differences in meaning.

What is the Meaning of Bilabial Sounds?

Bilabial translates to two-lips, meaning that bilabial sounds involve both lips. This can be a full or partial closure between the lips.

Bilabial: sounds that involve a constriction at the lips.

Bilabial sounds are a type of consonant sound that is produced using both lips. In phonetics, they are classified as plosives, nasals, or approximants depending on how the sound is produced. Sounds with a bilabial constriction include bilabial consonants and rounded vowels.

Rounded vowels include vowels like [u] as in boot and [o] as in boat. If you say boo, you can feel that your lips are tightly rounded and pushed forward. The other rounded vowels are [y, ʉ, ʊ, ø, ɵ, œ, ɞ, ɔ, ɶ, ɒ].

Bilabial consonants can occur with just about any manner of articulation. The only exception is lateral consonants, which must involve a constriction with the tongue. Here's a summary of the bilabial consonants.

Bilabial Sound Transcription
IPA TranscriptionPhonetic Transcription
pvoiceless bilabial plosive
bvoiced bilabial plosive
mbilabial nasal
ʙbilabial trill
ɸvoiceless bilabial fricative
βvoiced bilabial fricative
ʍvoiceless labial velar approximant
wvoiced labial velar approximant
ʘbilabial click
ɓvoiced bilabial implosive

Some bilabial sounds, like the voiceless bilabial nasal and voiceless bilabial trill, can appear in languages but do not have a unique IPA symbol. These sounds are marked with diacritics: symbols written above or below IPA symbols to indicate a change in articulation. The voiceless bilabial trill, for example, is written as the voiced bilabial trill with the voiceless diacritic: [ʙ̥].

There are four bilabial consonant phonemes (a meaningful speech sound) in English: bilabial plosives [p] and [b], bilabial nasal [m], and voiced labial velar approximant [w].

Bilabial Plosive

The bilabial plosives are the [p] and [b] sounds; these sounds are very common in the world's languages. These sounds are also referred to as bilabial stops because they briefly stop the flow of air through the mouth.

When you produce a voiceless bilabial plosive [p], as in petal or apple, you completely close the lips for a short period. During the closure, you push air out of the lungs, increasing the air pressure inside the mouth. This creates an imbalance in air pressure just like the bilabial click; this time, though, the air pressure in the mouth is higher than the air pressure outside the mouth. When you release the closure, the air bursts out of the mouth to equalize the pressure. This whole process happens in a matter of milliseconds!

The voiced bilabial plosive [b], as in bench or bubble, follows the same process with one exception. During or immediately after the release of the closure, the vocal folds start vibrating, resulting in voicing.

To tell if a sound is voiced, place your hand on the front of your neck and produce the sound. If you feel a "buzzing" vibration, the sound is voiced!

Bilabial Fricative

You may not immediately recognize the voiceless bilabial fricative [ɸ] because it's not a phoneme in English. You probably produce this sound fairly often, though. When you blow out a candle, you produce a voiceless bilabial fricative. The voiced bilabial fricative [β] is produced the same way with the addition of vocal fold vibration.

Bilabial, Blowing out a candle with a bilabial fricative, StudySmarter

Fig. 1 - You use a voiceless bilabial fricative to blow out a candle.

Acoustically speaking, a bilabial fricative is a turbulent stream of airflow through a narrow constriction at the lips. When you produce a bilabial fricative, you create a very narrow passage at the lips and force air quickly through it. The result is the "fuzzy," static-like sound of a bilabial fricative.

Bilabial Trill

The bilabial trill [ʙ] is a rather fun bilabial consonant. You might be familiar with the concept of "rolling your Rs," as this is taught to Spanish learners. The rolled r in the Spanish word perro is called an alveolar trill.

To keep with the conventions of "rolling your Rs," think of a bilabial trill as "rolling your Bs." To produce a bilabial trill, you force air from your lungs through lightly-closed lips. This causes your lips to repeatedly flap apart and back together. This bilabial trill also involves vocal fold vibration, meaning that it is a voiced sound.

Bilabial trills appear in the Bantoid languages of Sub-Saharan Africa, as well as the Uralic language family. Some people use the bilabial trill to mimic the sound of an engine rumbling.

Other Bilabial Consonants

The other bilabial consonants are the nasal, approximants, click, and implosive.

Bilabial Nasal

The bilabial nasal is the [m] sound, as in hum or mad. Nasal sounds are produced using the velum.

Velum: or soft palate, is the soft, fleshy area at the back of the mouth that controls airflow through the nasal cavity.

Bilabial, Vocal tract diagram with labeled velum, StudySmarte

Fig. 2 - The velum raises and lowers to control airflow through the nasal cavity.

When you produce a bilabial nasal, you completely close your lips, lower your velum to allow air to flow through your nose, and allow your vocal folds to vibrate. This results in a voiced sound that resonates within your nasal cavity and enters the environment through your nose.

If the air is coming out through your nose, how can you tell that the closure is bilabial? The best indicator of the place of articulation for nasals is actually context. Moving to and from a nasal with other consonants and vowels provides the most information about the placement of the nasal. Without acoustic context, it's more difficult to tell where a nasal occurs. Try this for yourself: produce different nasal sounds with no context ([m], [n], and [ŋ]) at a friend while they close their eyes. Have them guess which sounds you're producing. They'll probably find the task harder than they would with acoustic context (like [ma], [na], or [ŋa]).

Labial Velar Approximants

The [w] sound in water is a voiced labial velar approximant. It's produced like a very short [u] vowel: the lips come closer together without completely closing, and the back of the tongue tenses up near the velum.

Some dialects of English (Irish English and Southern U.S. English, for example) pronounce the sound at the beginning of words like what and where as a voiceless labial velar approximant [ʍ]. You'll also produce a [ʍ] if you say the word water in a whisper.

Bilabial Click and Implosive

The bilabial click [ʘ] is a voiceless sound that resembles a "smacking" of the lips. When you produce a bilabial click, you close your lips fully, "sucking in" air during the closure. This creates an environment where the air pressure inside your mouth is lower than the air pressure outside it. When you release the closure, the air pressure quickly equalizes, causing a click sound. This sound appears in languages spoken in Southern and Western Africa and in the South Pacific region.

Like the click, the bilabial implosive [ɓ] is produced by closing the lips and decreasing pressure inside the vocal tract. Instead of sucking in air with the tongue, though, you decrease pressure by lowering your larynx (a.k.a. your "voice box") to lengthen your vocal tract during the closure. The result is a quieter, voiced sound on the release of the closure. This sound can appear in a very thick Texas accent. Think of a sheriff in a Western movie saying whatcha got there, boy? The b in boy is a bilabial implosive.

Bilabial - Key takeaways

  • Bilabial sounds are sounds that involve a constriction at the lips.
  • Sounds with a bilabial constriction include bilabial consonants and rounded vowels.
  • The lateral manner of articulation can't be produced in the bilabial area because laterals require a constriction with the tongue.
  • The rounded vowels are [y, ʉ, u, ʊ, ø, ɵ, o, œ, ɞ, ɔ, ɶ, ɒ].
  • The bilabial consonants include plosives, nasals, trills, fricatives, approximants, clicks, and implosives.

Frequently Asked Questions about Bilabial

There are ten distinct bilabial consonants in the International Phonetic Alphabet (IPA). These include bilabial plosives, fricatives, trills, nasals, approximants, clicks, and implosives. 

Bilabial translates to two-lips, meaning that bilabial sounds involve both lips.

There are four bilabial consonant phonemes in English: bilabial plosives [p] and [b], bilabial nasal [m], and voiced labial velar approximant [w].

When you blow out a candle, you produce a voiceless bilabial fricative. You create a very narrow passage at the lips and force air quickly through it. The result is the "fuzzy," static-like sound of a bilabial fricative.

Bilabial sounds are sounds that involve a constriction at the lips. Sounds with bilabial constriction include bilabial consonants like [p, b, m] and rounded vowels like [u, o].

Test your knowledge with multiple choice flashcards

Sounds with bilabial constriction include _____ and _____.

Bilabial consonants can occur with any manner of articulation except:

[p]What is the articulatory description of this bilabial consonant?

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