To describe speech sounds, it is necessary to know what an individual sound is, and how each sound differs from all others.

When we know the language we hear the individual sounds in our “mind’s ear” and are able to make sense of them, unlike the sign painter in the cartoon.

Such sounds are not speech and are therefore not able to be segmented into the sounds of speech.

The lack of breaks between spoken words and individual sounds often makes us think that speakers of foreign languages run their words together, unaware that we do too.

Everyone who knows a language knows how to segment sentences into words, and words into sounds.

This ability is more surprising because no two speakers ever say the same word identically.

Our knowledge of a language determines when we judge physically different sounds to be the same.

We know which aspects of pronunciation are linguistically important and which are not.

The science of phonetics attempts to describe all of the sounds used in all languages of the world.

Acoustic phonetics focuses on the physical properties of sounds;

Auditory phonetics is concerned with how listeners perceive these sounds

Articulatory phonetics is the study of how the vocal tract produces the sounds of language.

Orthography, or alphabetic spelling, doesn't represent the sounds of a language

Phonetics is a science. We must devise a way for the same sound to be spelled with the same letter every time, and for any letter to stand for the same sound every time.

Spelling reformers failed to change our spelling habits, and it took phoneticians to invent an alphabet that absolutely guaranteed a one sound-one symbol correspondence

Each character of the alphabet had exactly one value across all of the world’s languages.

The inventors of this International Phonetic Alphabet, or IPA, knew that a phonetic alphabet should include just enough symbols to represent the fundamental sounds of all languages.