Goal of Lab 6:

In this lab, we are going to explore the acoustic correlates of obstruent place of articulation. We shall see that the location of these correlates differ in stops vs. fricatives: while they are mainly “intrinsic” (within the consonant) for fricatives, they are mainly “extrinsic” (in the transitions to adjacent vowels) for stops. This phonetic fact can help to explain cross-linguistic phonological restrictions on adjacent consonants.

RECORDING

Go to eClass and download the zip file “Lab6_Soundfiles”, containing the following files. Note, you can also generate these sound files or, optionally, you can use your “a_stop_a.wav” and “a_stop.wav” files from Lab 2 and generate the other two sound files.

File name Sounds to record
Lab6_a_stop_a.wav apa, aba, ata, ada, aka, aga
Lab6_a_stop.wav lap, lab, bat, bad, rack, rag
Lab6_i_stop_i.wav ipi ibi, iti, idi iki, igi
Lab6_a_fricative_a.wav afa, aθa, asa, aʃa, aha


INSTRUCTIONS

SECTION I. STOP CONSONANTS

Several acoustic correlates distinguish different places of articulation in stops. The main ones are:

  • VOT
  • Spectral pattern during aspiration (voiceless stops)
  • Transition into the adjacent vowels


We will focus on formant transitions in this section; we will discuss VOT and spectral pattern in class. Focus on the differences associated with place of articulation (i.e. the differences between /p b/, /t d/ and /k g/.

  • Open the following sound files in Praat: “Lab6_a_stop_a.wav” and “Lab6_i_stop_i.wav”
  • Focus on the voiced stops for now.


  1. In Table 6.1, note down the formant transition shape (particularly F2) between each voiced stop and the following [a] or [i] vowel (see Figure 6.1). Zoom in so that you can clearly see the formant transition from the stop into the following vowel.

  2. Note down the movement contour of F2 (and F1 if you can see it) into the following vowel.


Figure 5.1: Formant transitions from the stop to the following vowel
Figure 5.1: Formant transitions from the stop to the following vowel


SECTION II. FRICATIVES

Different places of articulation in fricatives are correlated with two main properties: spectral content and relative amplitude. By examining the overall spectral contour, peak frequency and the amplitude of peak frequency, we can have an idea of the properties of a fricative.


  1. Use Table 6.2 to fill in the measurements you take on these three dimensions and compare between fricatives of different POA.


For this portion of the lab, make sure that the spectrogram is set to display frequencies up to 9000 Hz:

  • Spectrum > Spectrogram settings…

  • View range: up to 9,000 Hz

  • Open the following sound file in Praat: “Lab6_a_fricative_a.png”

  • Select approximately 40ms in the middle of each fricative

  • Spectrum > View spectral slice

  • For each fricative:

    • Take a screenshot of the spectral slice and paste it into your lab Word document. (If you can’t remember how to do this, refer to in in LAB 1 Figure 1.10). Be sure to give the spectral slice an appropriate title.
    • Note down the spectral peak in Table 6.2: the frequency or frequencies around which most of the energy is centered, i.e. the highest amplitude frequencies (the highest peaks)
    • Note down the amplitude of the peak frequency or frequencies in Table 6.2 (this is the amplitude of those noted down in the previous bullet point). Note that the positive dB values are louder than the negative dB values
Figure 5.2: Fricative spectral analysis
Figure 5.2: Fricative spectral analysis


TIP:
You can also get a good idea of the frequency ranges and their relative amplitudes by looking at the spectrogram.

For English, ‘ballpark’ measurements for [s] will be around 9,000Hz or higher, and for [ʃ] will be somewhere close to 5,000Hz.



LAB 6 REPORT

SECTION I. STOPS

Table 6.1 Acoustic correlates of place of articulation in stops: formant transitions

Correlate Stops [b] [d] [g]
1. Formant transitions [i] context
[a] context


Q1: How do the different places of articulation differ with respect to the F2 transitions into the following vowels? What causes these differences?

Q2: Looking specifically at [ada] and [idi], do you notice a difference in the formant transitions? What do you think causes this difference?


SECTION II. FRICATIVES

Table 6.2 Acoustic correlates of place of articulation in fricatives

Peak frequency (Hz) Amplitude of peak frequency
[f]
[θ]
[s]
[ʃ]
[h]


Q3: Among the fricatives you measured, which ones are highest/lowest in amplitude? What do you think is the reason for this (think about articulation)?

Q4: Compare the spectral peaks of [s] vs. [ʃ]. What do you think causes the difference between these two fricatives?


REFERENCES

Q5: Provide a reference and very brief summary of one academic paper that uses the methods covered in this lab.

Disclaimer: The original lab materials on which this lab is based was put together in 2015 (updated 2019) by Sonya Bird, Qian Wang, Sky Onosson, and Allison Benner for the LING 380 Acoustic Phonetics course at the University of Victoria. Their materials are released under a Creative Commons license (CC BY-NC-SA 4.0) which allows for non-commercial use as well as copying and distribution and the creation of derivative works for non-commercial purposes. Thomas Kettig (with assistance from Taylor Potter) has modified these materials as needed for the York University LING 4220 Acoustic Phonetics course.