Week 07 Audiometry Lab Flashcards Preview

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Flashcards in Week 07 Audiometry Lab Deck (13)
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1
Q

What is intensity in relation to sound?

2 equations

A

an objective measurement of the average power (P) of sound incident perpendicular to to surface area (A) … unit of W/m2

J = P/A

can also be the square of effective pressure (Peff) over acoustic impedance (Z)

J = Peff2/Z

2
Q

What is loudness?

What does it depend on?

A
  • a subjective psychophysical quantity representing how loud we feel** **a sound of given intensity
  • depends on **frequency **and intensity
3
Q

What equation determines loudness?

What is its unit and how does it relate to “loudness level” units?

A

Stevens’ Law:

Lson = 1/16 (J/J0)0.3

(AKA power law)

  • unit is sone
  • 40 phon = 1 sone
  • sone/loudness doubles every 10 phon increase
    • ex: 50 phon = 2 sone, 60 phon = 4 sone
4
Q

How is the speed of sound waves calculated?

What is the speed of sound in air?

A

speed (c) is product of wavelength and frequency

c = λ ⋅ f

Csound in air is approx. 340 m/s

5
Q

What is loudness level?

What is its unit?

A

a comparitive and subjective measurement of a pure tone of any frequency that is equal to the dB of a sound at 1,000 Hz that is perceived as just as loud

Lphon = JdB 1000Hz

  • measured in phon
6
Q

What graph shows the dependence of loudness on frequency and intensity?

Explain it and draw it.

A

equal loudness curve (AKA Fletcher-Munson curve)

  • a intensity vs. frequency graph (normal y-axis, log x-axis) with isophon (equal loudness) curves showing sounds of the same loudness level
7
Q

What kind of wave is sound?

How does it oscillate?

A
  • sound is a mechanical wave which results from a periodic variation in pressure
  • it requires a medium and cannot exist in vacuum
  • sound waves are longitudinal waves which oscillate in the same direction of their propagation
8
Q

What is the dependence of the speed of sound on medium density?

Temperature?

A
  • a denser medium results in a faster propagation
    ex: Cair = 340 m/s, Cwater = 1,484 m/s
  • in a gaseous medium (such as air), higher temperature results in faster propagation

(despite a decreasing density with increasing temp.??? still don’t really get this)

9
Q

What does 0 phon correspond to?

How has the significance of 0 phon changed over time?

What does 130 phon correspond to?

A
  • 0 phon is the hearing threshold or minimum audible loudness
  • because of increased exposure to loud noises, the hearing threshold has actually increased to approx. 4 phon
  • 130 phon is the threshold of pain
10
Q

What is reference intensity?

A

the sound intensity that can just be heard at the reference frequency of 1,000 Hz

  • written as J0
  • determined to be J0= 10-12 W/m2

or

0 dB

11
Q

What is the reference sound?

A

a harmonic sound wave of 1,000 Hz used as a reference in audiometry

12
Q

What is sound pressure?

A

a harmonic pressure variation superposed on the equilibrium pressure of its medium (patm)

p(t) = p1 sin(ω0t)

13
Q

How is hearing loss calculated?

What is its unit and why?

A

loss = measured hearing threshold - normal hearing threshold

  • measured in dB because phon and sone apply only to healthy individuals