Psycholinguistics/Acoustic Phonetics LEAnswers
Learning Exercise 1
1. frequency = # cycles / second
frequency = 1 cycle / 6.25 seconds
frequency = 0.16 Hz
2. The wave deviates as far as one decibel away from baseline, thus the amplitude is 1 dB.
3. Recall that the human ear can detect sound with frequencies between 20-20,000 Hz and from 0-100 dB. The loudness of the sound would be just detectable, but the pitch would be inaudible, thus humans could not hear the noise.
Learning Exercise 2
1. Specrogram 1 is September.
Explanation: If you follow along the spectrogram, you will see the "noise" beginning the word which represents the fricative "S" in September. You can then see the formant patterns for the "e" immediately following the "s" and the double stop "pt" with a low frequency voicebar coinciding with the "p" and aspiration following the "t". This information alone should be enough to tell you that the word is September, not May, but also noteworthy is the third stop representing the "b" where is looks like stopped activity before the end of the word. (Hint: You may also want to remember what the "er" at the end of the word looks like, as this could help you with the next questions!)
Spectrogram 2 is October.
Explanation: You can see the "o" vowel formant patterns beginning the word, but the double stop ("c" + "t") is what really gives this one away. Notice that there is aspiration following each stop. If you look closely, you can see that F2 is lowering as the second, long "o" is pronounced. We learned that this is typical when our lips move from an unrounded to a rounded position (for a reminder, click [Psycholinguistics/Articulatory_Phonetics#Diphthongs|here]]) to see the bottom of the paragraph on diphthongs. We can clearly see another stop representing the "b" following this "o", and then the "er" formant pattern as seen in Spectrogram 1, September, ending the word.
Spectrogram 3 is February.
Explanation: Because we do not see the "er" pattern at the end of the word (as in the previous Spectrograms, 1 and 2), we can determine that the word is February and not November right away. Other significant indications are the fricative beginning of the word (representing "f") and the stop before the middle of the word (representing the "b"). Although November contains a stop ("b"), it is toward the end of the word, and in this case we see the stop toward the beginning of the word. Thus we can confidently infer that the word is February. Also noteworthy is the loudness of each sound represented by the darkness of the formant patterns. The "e" sound and the "a" sound (shortly after the stop, "b") seem to be loudest and thus most stressed, which is true when one says the word "February" (try saying it out loud!). This provides us with further confirmation the the word is indeed February.
Spectrogram 4 = August
Explanation: Although this spectrogram may appear quite messy, many of the tactics used to identify the word being produced in the first three problems can be used again here. We see that the first sound is the loudest, as it has a darker formant pattern. This makes sense because the main stress in the word "August" is the initial "au" vowel sound (try saying it out loud). We can then see a quick stop, represent the "g", more vowel formant patterns corresponding with the "u" and long fricative marks where the "s" occurs. At the end of the word after the "s" there is a quick stop where the "t" is produced and aspiration marks.
2. The stops and fricatives beginning and ending most of the words make it very possible to determine where word boundaries lie. The first word, "don't", is very short in the sentence and although the formant patterns aren't entirely clear, the fricative ("s") shows the beginning of the next word, "stop", and thus the end of "don't". The fricative occurs close to the beginning where and looks similar to a stop, but with high frequency noise. Before the "s", the stop "t" in "don't" can be noted and is followed by a small amount of aspiration. Since "stop" ends in a stop, it is fairly easy to identify it's ending - where there is a long lack of action. The stop pattern is particularly long, but this is probably due to the back to back "p" (at the end of stop) and "b" (at the beginning of believing). Although it is difficult to see exactly where stop actually ends and believing begins, we know that the rest of the spectrogram after the large stop can be attributed to the rest of the last word, believing.