To start thinking about how different sounds are made, we can consider an strange phenomenon. Even when we can hear no noise, we can often tell what a person is saying just by looking at their mouth; in other words, we are able to lip read, just as many people with hearing difficulties do. But how does this work?
We have all learnt, albeit subconsciously, from our contact with spoken language that certain mouth shapes produce certain sounds. We can describe how we make sounds by saying what we do with out lips, teeth and tongue, and how the air is released. To be able to explain sounds in a more 'scientific' manner, however, it's useful to know a little bit about the anatomy of our mouth and throat.
The diagram of the vocal tract on the right (from the University of Indiana) shows the main organs of speech. To learn more about the organs of speech, I highly recommend that you play with the RSC's interactive website.
The International Phonetic Association has developed a system of describing sounds using terminology based on the organs of speech. If we take the phoneme /b/ as an example, we know that to make this sound we start with our upper and lower lips together. We then let the air out in a rapid burst, rather like a little explosion. According to the IPA description, /b/ is a bilabial plosive.
The term bilabial refers to the place of articulation. According to the standard English consonant phonemes, there are 10 places of articulation. These are:
- bilabial (both lips together)
- labio-dental (upper teeth touch lower lip)
- dental (tongue between teeth)
- alveolar (tongue on alveloar ridge)
- post-alveolar (tongue just behind the alveolar ridge)
- palato-alveolar (tongue between alveolar ridge and palate)
- palatal (tongue on palate)
- velar (tongue on velum)
- glottal (using the glottis)
- labial-velar (lips together and tongue close to velum).
We saw that /b/ is also described as a plosive. This refers to the manner of articulation. There are six manners of articulation commonly found in English. These are:
- Plosive (a total blockage followed by a quick release of air, like an explosion)
- Fricative (a slower and restricted release of air - think of friction)
- Affricate (a combination of the previous two, air is initially blocked then released with restrictions)
- Approximant (a near but not total blockage of airflow)
- Nasal (the air comes out of the nose)
- Lateral (air escapes from the sides of the mouth, such as in the phoneme /l/)
In addition to the place and manner of articulation, we can say that a consonant is voiced or voiceless. Put your fingers on your Adam's apple for a moment and say something. Can you feel the vibrations? That's because your vocal chords are being used. If a sound is voiced, it is because the vocal chords are used. But we don't always used our vocal chords to make consonant sounds - in fact, almost half of the consonant phonemes in English are voiceless, meaning that there is no movement made in our larynx.
You may come across some classifications which refer to aspirated and unaspirated sounds rather than voiced and voiceless. This can be a little confusing, as generally voiced sounds are unaspitated and voiceless ones are aspirated. Aspiration refers to the airflow that is produced, and there's an easy test we can do to find out if a phoneme is aspirated or not. Put your hand, or even better, a sheet of paper, in front of your mouth. Now make the sound /b/. Does it move? Now make the sound /p/. Did you notice the difference? /b/ is an unaspirated sound, and the paper shouldn't have moved. /p/, on the other hand, is aspirated, and the paper should have moved a lot.
To see a chart of the phonemes of English and their respective classifications, click here. The consonants on the left side of each column are voiceless, whilst those on the right are voiced. Please note that this table, produced by the IPA, features phonetic symbols, so there might be some that you are not familiar with.