WAVES (PART 4)

Question 1

1. What is a Sound Wave?

Answer 1

• it is a moving disturbance of the molecules of air

Question 2

2. What are Compressions?

Answer 2

• they are the areas where the molecules of air are closer together

Question 3

3. What are Rarefactions?

Answer 3

• they are areas where the molecules become more sparse

Question 4

4. What results in the sensation of sound?

Answer 4

• when the compressions and the rarefactions of the
  waves strike the eardrum
• this will only happen when the frequency of the waves
  is between 20Hz and 20 00Hz

NB: the wave will go in the same direction as the particle
movement

Question 5

5. What are Ultrasonic waves?

Answer 5

• they are waves that have a frequency of above 20 kHz

Question 6

6. What are Infrasonic Waves?

Answer 6

• they are waves that have a frequency of below 20 Hz

Question 7

7. What are Acoustic Waves?

Answer 7

• they are waves that have a frequency between 20Hz and 20kHz

Question 8

8. What does the speed of sound depend on?

Answer 8

• it is not fixed
• it depends on the material through which the wave is
  travelling

NB: an increase in the stiffness of the medium of the speed of sound leads to an increase in the sound

Question 9

9. What equation allows for us to predict the Speed of Sound?

Answer 9

• the Bulk Modulus is the same as the Young’s Modulus

Question 10

10. What is the speed of sound in air that has a temperature of 0°C?

Answer 10

• 331 m/s

Question 11

11. What is the speed of sound in air that has a temperature of 20°C?

Answer 11

• 343 m/s

Question 12

12. How much does the speed of sound increase with a 1°C rise in temperature?

Answer 12

• the speed increase by about 0.61 m/s

Question 13

13. What equation would we use to relate the speed of sound to temperature?

Answer 13

Question 14

14. What is the speed of sound independent of?

Answer 14

• pressure
• frequency of the wavelength
  (this is objective and measurable)

Question 15

15. What is Pure Tone?

Answer 15

• it is a sound wave
• it has an amplitude that varies sinusoidally
  (its movement looks like a sine curve)

Question 16

16. What are two things that we associate with Pure Tone with regards to hearing?

Answer 16

• pitch
  (this is subjective)
• loudness

Question 17

17. What is Pitch?

Answer 17

• it is how high or low something sounds
• it is also where the sound lies on a musical scale
  (this is determined by the frequency)
• it will define the tone of the sound

Question 18

18. What does a higher frequency result in?

Answer 18

• a higher pitch

Question 19

19. What is the difference between Pitch and Frequency?

Answer 19

PITCH:
- describes a subjective impression
- this is also a psychological one

FREQUENCY:
- it objective
- it is a measurable property

Question 20

20. What is Loudness?

Answer 20

• a measure of the human perception of sound

Question 21

21. Is the relation of intensity and loudness linear?

Answer 21

• no
• a sound wave of high intensity is perceived as louder

Question 22

22. What is the sensation of sound roughly proportional to?

Answer 22

• the logarithm of the sound intensity

Question 23

23. What is the intensity or the loudness level (L l) defined by?

Answer 23

• it is defined by an arbitrary scale
• this scale corresponds roughly to the sensation of
  loudness

Question 24

24. What is a zero on the Sensation of Loudness scale?

Answer 24

• it is taken at the sound wave intensity of:
  L0 = 1.00 x 10⎺¹² W/m²

Question 25

25. How is the intensity ratio calculated?

Answer 25

• the unit is in dB
• this is a dimensionless unit
• it is used to represent the relative magnitude of
  intensities

Question 26

26. How is the sound intensity level calculated?

Answer 26

• the unit is in dB

NB: a 20 dB increases in intensity levels results in a 10²
increase in intensity

Question 27

27. What is the dB scale used to indicate?

Answer 27

• relative magnitudes
• the absolute acoustic unit is often written as dB SPL
  (sound pressure level)

Question 28

28. How is dB SPL calculated?

Answer 28

Question 29

29. What are speech sounds produced through?

Answer 29

• they are produced through the movement of organs
• these constitute to the vocal tract
• this vocal tract acts on the air in the respiratory
  passages

Question 30

30. What do the vocal organs generate?

Answer 30

• they generate a local disturbance on the air
• they generate this at several positions in the vocal tract
• this creates the sources for speech production

Question 31

31. What are Acoustic Waves generated by?

Answer 31

• they are generated by sources such as vocal organs
• they are then modified during the propagation through
  the vocal tract

Question 32

32. What are two factors that contribute to the Structure of Speech sounds?

Answer 32

• these are generated by the combined effect of sound sources and vocal tract characteristics

Question 33

33. What factors make up the Vocal tract?

Answer 33

• the cavities of the mouth
• the nasal cavity
• the pharynx

NB:
- changes in the shapes of these areas produce different
sounds
- they have huge flexibility
- this allows us to generate different tones

Question 34

34. What is needed to create sound?

Answer 34

• an energy source

Question 35

35. What is most of human speech and communication carried out by?

Answer 35

• it is carried out by using air from the lungs while
  exhaling