Bilabial plosives /p/ and /b/

/p/ is unvoiced and is the counterpart to the voiced /b/. With /p/ and /b/, the lips are the tools to stop the air, and then pop the air. To create /p/ and /b/, air is briefly prevented from leaving the vocal tract by closing the lips. The sound is aspirated when the air is released. To make /b/, we need to vibrate the vocal cords to make it voiced. The aspiration for a /p/ is far greater than the aspiration for a /b/, and, for this reason, voiced plosives are not viewed as having aspiration. When we do not use aspiration when needed, we can confuse our listeners. For example, if we said “pill” without aspiration, people might think we said “Bill.”

Words with /p/

As we learned in the previous section on the allophones of plosives, words with voiceless plosives can have three different sounds, aspirated, unaspirated and unreleased. That is, /t/, /p/ and /k/ are pronounced in English with aspiration either initially or in stressed syllables, but without aspiration in non-initial, unstressed syllables. So we examine words with ‘p’ based on these three allophone types. 

Words with aspirated p, [pʰ]

When /p/ comes at the beginning of a word or at the beginning of a stressed syllable, it is an aspirated  [pʰ]. These  words  have aspirated  [pʰ] sounds as ‘p’ comes at the beginning of the word: 

pin, pie, part, pause, pocket, problem, prevent, put, plain, please, park, propose 

These  words have aspirated  [pʰ] sounds as ‘p’ comes at the beginning of a stressed syllable:

appear, appearance, computer,  opinion, report, support 

Words with unaspirated p, [p]

When /p/ does not come at the beginning and does not begin a stressed syllable, it is not aspirated, These words with ‘p’ are unaspirated:

company, apple, opera, stupid,  typical, shopping

Also, when /p/ is in a consonant cluster after /s/, it is unaspirated. There is no puff of air. 

spring, spade, display, expect, especially

 In the following words, the initial p is aspirated whereas the medial p is not:

paper, papa, people, piper, pepper, 

Unreleased p, [p̚]

When a plosive comes at the end of a word, it is often unreleased. 

develop, help, hope, shape, shop, stop, type, wipe,

Complementary Distribution vs free variation

Linguistically interesting facts about the relationships among  the three allophones of /p/, i.e., aspirated, unaspirated and unreleased, are these. Between aspirated and unaspirated /p/, if one sound occurs the other sound does not occur. That is, aspirated  /p/ occurs in the initial or stressed syllable, and unaspirated /p/ occurs in the non-initial or unstressed syllable. Linguists call this type of mutually exclusive occurrence of sounds the complementary distribution. By contrast, the unreleased /p/ at the end of a word is optional. That is, the /p/ can be released or not. Linguists call this type of interchangeable occurrence of sounds the free variation.

Silent /p/ words

When /p/ is pronounced, it is pronounced as one of its three allophones: aspirated, unaspirated or unreleased. But the letter P is silent in some words. These are some rules relating to the silent P. First, if the P is followed by an N, S, or T creating a "PN", "PS", "PT" bond, especially at the beginning of a word, then the P is silent. For example, pneumonia, psychic, pterodactyl. The letter P is not silent if a "PN", "PS", or "PT" is in a separate syllable like capsize, flipside, upside, upset, heptagon, September, captain, caption, capture, rapture. 

Secondly, the P is silent in the following words: 

corps, coup, cupboard, raspberry, receipt, pseudonym, psalm 

Silent /b/ words

Compared with /p/, the pronunciation of /b/ is simple, as we do not need to worry about the aspiration element. Words with B can be tricky when the B is silent. These are two cases where B is silent. First,  B is not pronounced after M at the end of a word. These are examples: 

limb, plumb, numb, crumb, dumb, comb, bomb, thumb, climb, tomb. 

Second,  B is usually not pronounced before T. These are examples:

debt, doubt, debtor, doubtful, subtle

/p/ is harder to pronounce than /b/ since an aspirated /p/ is uncommon in most languages. So we have a few tongue twisters to practice /p/ and /b/ before we move onto minimal pairs:

Peter Piper Picked a Peck of Pickled Peppers.

A peck of pickled peppers Peter Piper picked.

If Peter Piper picked a peck of pickled peppers,

Where's the peck of pickled peppers Peter Piper picked?

Perry's Berry's make peanut butter better. 

Buy pie pans before you buy butter plates. 

/p/, /b/ minimal pairs 

These are minimal pairs for /p/ and /b/. Notice the differences in vowel lengths between words when /p/ and /b/ come at the end of the words. As we learned in the section on voicing, due to pre-fortis clipping, vowels are shorter before voiceless consonants. 

cab cap

big pig

buy pie

bet pet

bear pair

bill pill

bin pin

cub cup

Bob bop

band panned

base pace

bat pat

bear pear

belt pelt

berry perry

blade played

bay pay

rib rip

blank plank

bride pride

bull pull

butter putter

robe rope

breast pressed

beep peep

tribe tripe

/p/, /b/ sentences 

These are sentences with the /p/ sound.

Peter grows the most precious peaches and pears.

We had pumpkin pie and pepperoni pizza near the swimming pool.

Wipe your mouth with paper napkins.

Pull on the zipper to open your suitcase.

Under the dim lamp light, the painter mopped the damp floor.

The rope is tied in knots.

Please Wash your hands with soap.

Perfect planning prevents pathetic performance.

These are sentences with the /b/ sound. 

He shot the ball at the buzzer.

The bat hung upside down in the tree eating beans.

The bear was hunting for the young bobcat.

 I found corn on the cob in the cupboard

The baby was sleeping in her crib.

The bear cub turned the doorknob.

These are sentences with both /p/ and /b/ in them.

Paul peeped and beeped as the bull pulled his bus.

Bob ripped his rib on a big burly pig playing bagpipes.

The bishop blessed Pete the pageboy before his baptism.