The glottal stop is not generally used as a stand alone phoneme in EL learner dictionaries, hence it is not on the chart. And is not part of standard English spelling. In some languages however it is a natural part of the spelling system (see Wikipedia for a brief and interesting discussion). Nevertheless it comes up in teaching all the time.
In the IPA it is transcribed /ʔ/ like a question mark without the dot. It is an unvoiced sound (don’t believe me, check that out for yourself) and is produced by closing the glottis which stops the airflow. Thus it is also a stop sound.
Now, earlier this month I had the pleasure of taking the role of external pron tutor on the Oxford TEFL Distance Diploma Training Course, an excellent course with some really sparkling exchanges and discussions going on in the pron module. With their kind agreement I will excerpt a few of these exchanges in this blog during the next few posts. Here is the first:
Course member Liam MacCarron wrote: Hi Adrian,
1) How do you propose we help our learners with the glottal stop?
2) If you had been introducing the phonemes of words on the board to students for a few weeks, how would you represent the glottal stop even though it isn’t represented on the phonemic chart? Should we just use that question mark looking symbol, tell them that’s what it represents and move on? Or would that a nice intro to allophones for them?
Hi Liam, I would help them in the same way as for any other sound. They can easily find it by saying any vowel repeatedly and quickly and then slowing down the repetition, then isolating what they do between each vowel. It is probably not a new sound for them. Once they can say it I would give it a symbol, as you say like a question mark without the dot, sort of sickle shaped. I would draw that on the board next to the chart, in a little box the same size as the symbols and boxes on the chart.
Since the sound is a stop sound, or plosive, I would position the new symbol at the end of the plosive row (the first row) of consonants. In fact geographically it fits well at the right of /g/ since the stop is produced at the back of the vocal apparatus, and is of course unvoiced.
Once you have got it on the map it is in circulation and available for use along with all the other sounds for making words, tracking connected speech, corrections and so on.
If you are using it as an allophone of /t/ you might want to indicate that it can be placed in the /t/ box along with all other allophones of /t/, but since it has other uses as well I would probably park it at the end of the stop row, as I said.
When practising I would often get them to say the word (eg butter) one way with the glottal stop /ʔ/ and the other way with /t/, so they don’t get fixated, and can feel the difference in their mouths and be able to choose. This will also help them to hear the distinction more discerningly.