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Audiology & ENT > Basic Acoustics & Terminology > Flashcards

Basic Acoustics & Terminology Flashcards

1
Q

What is sound?

A

Vibratory energy transmitted by pressure waves in air or other media that is the objective cause of the sensation of hearing

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2
Q

What are 4 sources of sound?

A

Taut cords
• Taut membranes

• Air in tubes
• Knocking

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3
Q

What do all sources of sound involve?

A

All involve moving or vibrating structures – energy is transferred from mechanical energy into sound energy

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4
Q

In sound transmission what happens when a sound source vibrates?

A

air molecules around the source vibrate and pass on the vibrations to the adjacent molecules

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5
Q

What is the result of sound transmission?

A

waves of high pressure (compression) and low pressure (rarefaction) travel through the air

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6
Q

What happens as a sound wave moves out from its source?

A

energy is dissipated in the form of heat.

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7
Q

What happens when energy is dissipated in the form of heat?

A

the energy of the sound wave decreases as the distance from the source increases.

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8
Q

Does certain media pass sound more easily?

A

Yes

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9
Q

What is the speed of sound in air?

A

340m/s (760mph)

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10
Q

What is the speed of sound in water?

A

1500m/s (3350mph)

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11
Q

What can a vacuum not pass?

A

Sound energy

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12
Q

What is a sinusoid?

A

• Physically: a sine wave is made up of just one frequency of vibration of the air molecules
• Subjectively: the sound is clean and sharp – a “pure tone”

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13
Q

What produces a sinusoidal wave? (Sine wave)

A

A tuning fork produces the most basic sound.

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14
Q

What are the 3 physical characters of a sinusoid?

A

• Amplitude (Intensity)
• Frequency
• Phase

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15
Q

What is the amplitude of a sound?

A

a measure of the magnitude of pressure changes in the medium concerned (Sound Pressure Level SPL)

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16
Q

What is SPL?

A

Sound Pressure level

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17
Q

What is the simple answer for amplitude?

A

Loudness

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18
Q

What is amplitude measured in?

A

Newtons/m2= Pascal (Pa) or micropascals (uPa)

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19
Q

What does 0.000001 Pa =?

A

1uPa

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20
Q

What is the quietest sound heard for the human ear?

A

20uPa

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21
Q

What is the loudest sound tolerated for the human ear?

A

100,000,000 uPa (100Pa)

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22
Q

What is used to measure a sound level?

A

Decibels

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23
Q

What is dB derived from?

A

a ratio and must be referenced to an absolute amount

24
Q

What does dB=?

A

20log10(P/Pref)

25
Q

What does reference pressure is human 1kHz threshold=?

A

20uPa

26
Q

What are the advantages of the decibel scale?

A

• It has a zero baseline
• The just noticeable difference ~1–3dB
• Similar to human subjective perception of loudness, i.e. twice the dB level = twice loudness
• Human hearing range 0–140dB

27
Q

What is frequency?

A

Frequency is the number of wave cycles in one second.

28
Q

What is frequency in subjective terms?

A

Pitch

29
Q

What is frequency specified in?

A

Cycled per second- Hertz

30
Q

When does the frequency of a sound increase?

A

When the number of cycles per second increases

31
Q

What is the normal human hearing range in Hz?

A

20 t0 20,000Hz

32
Q

What can harmonics be found in?

A

• Musical instrument
• Electronic amplification
• Human voice

33
Q

What is the tone with lowest frequency called?

A

Fundamental

34
Q

What are other tones called?

A

Overtones

35
Q

What does Overtone with frequency that is a multiple of the fundamental frequency?

A

Harmonic

36
Q

What is the normal human ear able to do between many sounds?

A

detect, identify, and differentiate

37
Q

What is Pure tone Audiometry used for?

A

To assess patients’ hearing thresholds (quietest sound they can hear) over a range of frequencies

38
Q

What is the range of frequencies in air conduction?

A

250-8000Hz

39
Q

What is the range of frequencies in bone conduction?

A

500-4000Hz

40
Q

What range does Pure Tone Audiometry cover?

A

Speech

41
Q

What is a phase?

A

A description of where, at a point in time, the sound wave is during its repeating cycle

42
Q

What does Phase measure?

A

degrees or radians

43
Q

What can two waveforms have the same and different?

A

Same- frequency and amplitude

Different - phrase

44
Q

What happens if two sinusoids of the same frequency and same phase from different sources coincide?

A

The regions of positive pressure combine, as do the regions of negative pressure – constructive interference.

45
Q

What is destructive interference?

A

if the two signals are out 180o of phase the positive and negative portions cancel each other out

46
Q

What may Patterns of destructive and constructive interference lead to?

A

“dead” spots and “live” spots in auditorium acoustics

47
Q

What are room acoustics based on?

A
  • Sound reflection
  • Sound absorption
  • Reverberation
    • Attenuation
48
Q

What happens when sound meets a change in surface density?

A

some sound energy is absorbed, some is reflected and some is lost as heat.

49
Q

What is reverberation?

A

The sound remaining after the sound source has stopped

50
Q

What is reverberation time?

A

• the time taken for the sound intensity to drop by 60dB from it’s original level

51
Q

What does direct sound always do?

A

arrives first, and always from the correct direction.

52
Q

What are there lots and lots of in precedence effect?

A

reflections from all surfaces and objects in the
room (i.e. reverberation)

53
Q

What is attenuation?

A

The stopping of sound by enclosure or shielding

54
Q

What does a dosimeter measure?

A

Level and frequency of sounds over time

55
Q

When must ear protection must be used when using a dosimeter?

A

80dB

Audiology & ENT (7 decks)

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