Basic Acoustics

Question 1

Waveform: what are the axes?

Answer 1

X: time
Y: amplitude

Question 2

Spectrogram: what are the axes?

Answer 2

X: time
Y: frequency
Greyscale: amplitude

Question 3

Sound wave def?

Answer 3

variation in pressure over time

Question 4

Sine wave?

Answer 4

• simplest kind
• pure tone
• periodic, smooth, symmetrical

Question 5

Amplitude def? (diff between…)
measured in…?

Answer 5

• difference between peak pressure and average atmospheric pressure
• ie. top of wave minus midline
• measured in pascals or micropascals

Question 6

Intensity def? Measured in…?**

Answer 6

• power transmitted by a wave
• measured in dB
• dB = logarithmic scale!!

Question 7

cycle def?

Answer 7

one complete round trip in a periodic wave

Question 8

period (T) def?

Answer 8

amount of time required for 1 cycle (in s or ms)

Question 9

frequency def? equation? units?

Answer 9

• cycles per second
• f = 1/T
• Hz

Question 10

Equal loudness contour? Measured in? Important thing to know?

Answer 10

• frequencies that all sound the same loudness when played at the same amplitude
• phones = loudness measure
• MORE SENSITIVE to mid-upper range frqs

Question 11

Complex waves? How is it made up?

Answer 11

• tones of several frqs
• sine waves added
• amp of complex wave = SUM of amplitudes of its components

Question 12

Harmonic def?

Answer 12

whole number multiple of the fundamental frequency

Question 13

Harmonics in complex sounds ??

Answer 13

• complex sounds only have harmonics that are whole number multiples of the fundamental frq

Question 14

Aperiodic waves: what important 2 things don’t they have?

Answer 14

• no repeating cycles
• no harmonically related component waves

Question 15

White noise?

Answer 15

equal-amplitude components at all
frequencies

Question 16

Source filter theory meaning?

Answer 16

• speech has a source (glottal airflow) that is modified by a filter (vocal tract) in order to make speech sounds
• it specifies the relative amount of energy passed through for each frq
  → some frqs amplified
  → some frqs dampened

Question 17

Source: what is it? what does the spectrum look like? what kind of wave is it??

Answer 17

• glottal airflow / vocal fold vibration
• highest amp. at lower frqs
• decreasing amp at higher frqs
• tail pointing to the right
• periodic / quasiperiodic
  (she asked this as a review question but didn’t give an answer and google doesn’t agree. take your best guess!)

Question 18

Filter: what is it? what does it do? what does it create?

Answer 18

• vocal tract (supra-laryngeal)
• specifies relative amount of energy at each frq
• creates FORMANTS
  → formants are the reinforced frqs

Question 19

Output: what is it?

Answer 19

• speech sounds / radiated signal

Question 20

Formant frqs def?? Important thing to note?

Answer 20

• peaks in the filter function of the vocal tract
• the resonances of the vocal tract
• the formant relation is most important (rather than the actual frq)