Homework on Ladefoged (2005) Chapter 9 ("Listening Computers")

The questions in this homework are in conjunction with the assignment to read Chapter 9 of Ladefoged (2005) on "Listening Computers".

Your answers are due in class on Monday, November 19, for discussion in class that day.

1. Probability of a spectral pattern given a segment -- In Chapter 9, Peter Ladefoged talks about the role of probability in different stages of speech recognition for different kinds of tasks. He describes, for example, the way that an ASR system might recognise the day of the week being pronounced in the utterance in Figure 9.2. Given the energy pattern, there is a high probability that the patterns of slices over the first 150 milliseconds of the signal will be better matches for the stored patterns for an s or for an ʃ than for a w. What stage of the speech recognition system in Figure 9.4 is involved when this pattern matching is done?
2. Word probabilities (1) -- Describe how this high probability of an s or ʃ match combines with the knowledge that the word is the name of a day to further limit the choices. What stage of the speech recognition system in Figure 9.4 would be involved if we knew for sure that the word must be the name of a day of the week?
3. Word probabilities (2) -- In making up the two pseudo-sentences (1) Note that is the speaker's lips together with two groups of a vowel in the air becomes too difficult when lamenting. and (2) Same the without vocal but air as itself repetition higher distinctiveness meaning major at standard absolute can the consider., Peter Ladefoged relied on different words having different probabilities. In one case he used raw probabilities and in the other he used conditional probabilities. Which is which?
4. Consonant and vowel probabilities -- What do the two barcharts in Figure 9.5 show? What is the difference between the barchart on the left and the barchart on the right in this figure? Why are these numbers important in speech recognition?
   Following up: Ladefoged talks about the small number of occurrences of ʒ and ʧ in the barchart on the right, but is this surprising, given the small number of occurrences of these two consonants in the barchart on the left? Are there other sounds that have more suprising numbers on the right given their numbers on the left?

The reading that is assigned for this homework is from the book:

Peter Ladefoged (2005). Vowels and Consonants: An Introduction to the Sounds of Languages. 2nd Ed. Blackwell.