Speech signals and symbols - background

Some basic terminology on language signs

The following terminology is helpful for making certain basic distinctions in the study of speech. For further background to this terminology, introductory textbooks to linguistics can be consulted.

1. Languages are sign systems, that is, they define methods for communicating information of many different kinds from one person to arbitrary numbers of other people.
2. Elementary signs are actions in one of the human behaviour modalities: visual, acoustic, tactile (and possibly olfactory and gustatory) modalities.
3. Actions are events produced by human beings, which may leave traces in the form of marks on objects, and artefacts. Written texts are examples of such traces. A simple distinction can therefore be drawn between event signs and trace signs.
4. Sign tokens are sign events which occur in a specific place at a specific time and are produced or understood by a specific person. Spoken (and other) sign event tokens are sometimes referred to technically as `signals', and Written tokens are sometimes referred to technically as `inscriptions'.
5. Tokens of the same kind (e.g. utterances of the same word or sentence) are referred to as sign types.
6. Signs are distinguished from other actions by being associated with two different areas of reality at the same time: Expression and Meaning.
7. Expression and Meaning may be related in different ways: as symbols, i.e. arbitrarily (the word expression `table' does not resemble its meanint, the the object it represents); as icons, i.e. on the basis of similarities (the word expression `moo' is similar its meaning, the sound it represents), or as indices, i.e. on the basis of proximity in space and time (a pointing gesture expression indicates an area of space and time which is relevant to its meaning).

Preparation for next week

1. Print yourself a copy of the IPA and
   • practise 2 consonants and 2 vowels which you think you have never pronounced before,
   • teach some-one else (parent, brother or sister, partner) how to pronounce these sounds.
2. Find out how to transcribe (and pronounce) the Welsh place name ``Llanfairpwllgwyngyllgogerychwyrndrobwllllantysiliogogogoch'', and teach some-one else how to pronounce it. Hint: search the web with Google ...
3. Check one of the sites which are linked to this page on `speech research' and look for definitions and examples of `oscillogram' and `spectrum'.
4. For those of you who have computers at home, find a `signal editor' program on the web (such as the demo version of GoldWave or CoolEdit ) and use it to examine any of the sound files on your computer.

The two domains of speech analysis

A fascinating puzzle in the speech sciences is that we perceive speech as being sliced up into discrete, separate units, like speech sounds, syllables, words, sentences. But when we investigate the physical properties of speech signals, we only see continuous changes between speech events, and not the slices which we perceive.

This very indirect relation between our categorial perception and our continuous measurements can be thought of as the symbol-signal barrier which we need to investigate, describe, and explain in our scientific study of speech.

This distinction defines the two basic areas of phonetics:

Symbol phonetics:

The description of the production and perception of speech sounds insofar as this can be represented as discrete categories by symbols, such as the symbols of the International Phonetic Alphabet, the IPA, as defined by the International Phonetic Association.
In Symbol Phonetics, the basic technique is the transcription of speech; the transcriptions may then be analysed in terms of structural and statistical models.

Signal phonetics:

The description of speech sounds in terms of their physical properties:

Articulatory phonetics:

the study of the physical, anatomical and physiological properties of the production of speech sounds;

Acoustic phonetics:

the study of the physical characteristics of the transmission of speech sounds;

Auditory phonetics:

the study of the physical, anatomical and physiological properties of the perception of speech sounds;

For some advanced information on acoustic speech signals you may want to check this previous class.