1. Remember me?
The number of times this happens in 1 second determines the frequency of the sound wave

2. Frequency If it happens 125 times per second We perceive it as pitch
125 cycles per second
125 Hertz (Hz)
We perceive it as pitch
middle C (about 260 Hz)
The higher the frequency the higher the pitch
This is the “fundamental frequency”
But there are other frequencies too

3. Harmonics Produced by smaller vibrations of the vocal folds
If the fundamental frequency is 100 Hz, you’ll have harmonics at 200 Hz, 300 Hz, 400 Hz, etc.
We “can’t” hear them

4. (fundamental frequency)
The harmonic series
The second harmonic
The first harmonic
(fundamental frequency)

5. The glottal wave

6. A 17-inch tube likes these frequencies

7. Source-filter model
The complex wave produced during a vowel is the result of two things:
The waves produced by the vibrating vocal folds (the source)
The way certain frequencies of the waves are amplified by the oral tract (the filter)
The vocal folds are a sound source, the oral tract is a sound filter
Example

8. Source-filter model The source provides a vowel’s pitch
The filter provides a vowel’s quality
Independent of each other

9. Vowel formants

10. Diphthong formants

11. A bit more on acoustics Yuning’s video Better video