Determine the Frequency of Each of the Following Waveforms

SPPA 4030 Speech Science

KEY: Practice Exercises: Acoustics Review

1. What is the name we give to the plot below? Amplitude spectrum

What kind of sound does it represent (e.g. simple periodic, complex periodic, aperiodic)? Why? Complex periodic sound Sound energy located at discrete frequencies at whole number multiples of each other

Does this sound have a fundamental frequency. If so, what is it? What is the fundamental period? Yes T=10 msec SPPA 4030 Speech Science

2. SPPA 4030 Speech Science

3. One the plot below, draw a line that represents the envelope associated with this sound. Is this a spectrum envelope or an amplitude envelope? How do you know?

4. Draw a frequency response curve for the following filters. a. High pass filter with cutoff frequency of 100 Hz. b. Low-pass filter with a cutoff frequency of 500 Hz. c. Band-pass filter with a lower cutoff frequency of 200 Hz and an upper cutoff frequency of 800 Hz. a.

+ n i a G

- 100 low Frequency (Hz) high b. SPPA 4030 Speech Science

+ n i a G

- 500 low Frequency (Hz) high

+ n i a G

- 200 800 low Frequency (Hz) high SPPA 4030 Speech Science

5. You have a client who has a vocal fold paralysis. As a result of this disorder, his speech is extremely soft. One of your therapeutic goals is to increase the client’s loudness of speech. You measure the average sound pressure level of the clients speech before and after your therapy. Pre-therapy sound pressure level was 11 pressure units (actual units doesn’t matter). Post-therapy sound pressure level was 23 pressure units. Calculate the increase in sound pressure level in decibels. dBSPL = 20log(23/11) = 6.4

Post therapy level is 6.4 dBSPL louder than pre-therapy level.

6. Express the following pressures in dBSPL with respect to the following reference pressure.

PREF 20 micropascals a. 200 micropascals b. 10000 micropascals c. 20000 micropascals d. 200000 micropascals e. 2 micropascals f. 1 micropascal

a. 20 dBSPL b. 54 dBSPL c. 60 dBSPL d. 80 dBSPL e. -20 dBSPL f. -26 dBSPL

7. A group of Parkinson’s patients were found to speak with an average sound pressure level of 12,000 micropascals. A group of healthy speakers spoke with an average sound pressure level of 20,000 micropascals. Express, in decibels, the difference in sound pressure level between Parkinsons’ group and the healthy control group. dBSPL = 20log(12000/20000) = -4.4

Parkinson’s patients speak at a sound pressure level that is 4.4 dB less than the control group. SPPA 4030 Speech Science

8. For these six plots, provide the name we give to this graph type, describe what type of sound the plot represents and match those plots that are plotting similar types of sounds.

Pressure waveform simple periodic sound Amplitude spectrum, aperiodic sound

Amplitude spectrum, complex periodic sound Pressure waveform aperiodic sound

Pressure waveform complex periodic sound

Amplitude spectrum, simple periodic sound SPPA 4030 Speech Science

9. Draw an amplitude spectrum of a sound that has the same harmonic structure as the sound below, but has a different spectrum envelope.

Draw an amplitude spectrum of a sound that has the same spectrum envelope as the sound below, but has a different harmonic structure.

10. You measure air pressure in your mouth during speech to be 5 cm H2O above atmosphere. Is this pressure measure a vector or scalar value? Why?

Vector value since air pressure may be above (positive) or below (negative) atmospheric pressure. It needs a sign to be interpreted. SPPA 4030 Speech Science

11. Draw a pressure waveform for a sinusoid that has a frequency of 200 Hz and a peak pressure of +/- 100 micropascals. Label axes with units and a number scale.

+100 Instantaneous Air Pressure -100 (micropascals)

5 10 15 20 25 Time (msec)

12. Draw an amplitude spectrum for a sinusoid that has a period of 10 milliseconds and a peak pressure of +/- 50 micropascals. Label axes with units and a number scale.

13. A 30 year old singer comes to see you complaining of problems producing a high notes when singing. Her speaking voice sounds normal. You record her producing a sustained ‘ah’. Looking at the waveform of the sustained ‘ah’, you measure the fundamental period to be 5.8 milliseconds. a. Based on our discussions in class, what kind of waveform would you expect it to be (simple periodic, complex periodic, aperiodic)?

Based on discussions in class, complex periodic. b. To your best ability draw an amplitude spectrum for the pressure waveform associated with her /ah/ production. Label axes with units and a number scale.

F=1/.0058=172 Hz SPPA 4030 Speech Science

It may look like the amplitude spectrum in question 14, except the peaks would be at 172 Hz, 344 Hz, 516 Hz, 688 Hz etc.

14. What would be the wavelength of a sinusoid with a frequency of 290 Hz? Speed of sound= 35000 cm/sec 121 cm SPPA 4030 Speech Science

Q15-17 SPPA 4030 Speech Science

Q 18-22. SPPA 4030 Speech Science

23. Below are three different types of plots stacked on each other.

Circle the correct answer to the following questions

i. Which plot is a wide band spectrogram? A B C

ii. Which plot is a sound pressure waveform? A B C

iii. Which plot is a narrow band spectrogram? A B C

iv. Which plot best shows the harmonic structure of the signal? A B C

v. Which plot best shows the formant structure of the signal? A B C