Speech sounds are made using organs that were evolved for other purposes and have been adapted into having an extra use - e.g. lungs, tongue, nasal cavity, teeth. In classifying speech sounds, the International Phonetic Alphabet (see chart) is organised in a way that reflects the function of the various organs involved in forming particular sounds. It shares some of the same symbols as are used in English writing (not necessarily for the same sound) as well as using some more obscure icons. For a "computer readable" version of the IPA, see here.

All sounds are made by moving air. Most speech sounds are pulmonic, that is to say the lungs are involved. Non-pulmonic sounds include clicks and ejectives, like the sound you might make if you emphasised the "s" of "yes".

The larynx contains the vocal folds (sometimes referred to as vocal cords), which is a pair of muscular tissue that can be held in different positions and consequently made to vibrate at different frequencies as air passes through it. When the vocal folds vibrate, this is voicing or phonation, and such sounds are called voiced sounds. Voiceless sounds are made when the vocal folds are open, and so they do not vibrate at all. Compare "ssss" sound (non-voiced) with "zzzzz" sound (voiced).

The voicing produced by the vocal folds results in intonation and contributes to the rhythm of speech. Intonation is an important way of conveying information such as expression when speaking. People who have surgery resulting in removal of the vocal folds (e.g. as a result of cancer) may be able to learn to speak using oesophageal voice (see Crystal p. 278), but such voice lacks intonation.

Vowels are always voiced; some consonants (e.g. "m" and "n") are voiced, others are non-voiced ("t" and "d"). The IPA chart distinguishes between the two by putting the non-voiced in the left hand side of the box, and the voiced in the right hand (e.g. "p/b"). Not all sounds have both versions (e.g. "m").

See diagram, p. A-8 of handout for description of all the vocal tract and parts of the mouth involved in making sound:

• upper lip
• lower lip
• nose
• upper teeth
• lower teeth
• tongue
• alveolar ridge (just behind the upper teeth)
• hard palate (roof of the mouth)
• soft palate, or velum (behind the hard palate) - this can be raised to close off the passage to the nasal cavity and make nasal sounds ("n"). Note that nasal sounds are not so forceful as oral)
• larynx
• epiglottis at the entrance to the larynx, and closes to stop food going down, but can be made to vibrate for certain sounds ("hhh" sound in spanish)

The tongue moves about and can articulate different sounds by touching the lips, teeth, alveolar ridge etc.. See Roach fig. 2.2 and handout for description of what goes on when you say the word "sand".

Useful book readings for this lecture:

• Roach: "Phonetics", ch. 2
• Fromkin: "An Introduction to Language", ch. 6
• Crystal: "Encyclopedia of Language", ch. 22