Acoustics Review Flashcards
1
Q
What is acoustics?
A
Science of sound
2
Q
What’s the key to being a sound source?
A
Having the ability to vibrate
3
Q
What must an object have to vibrate?
A
Mass & elasticity
4
Q
What is pressure dependent on?
A
The amount of force and the area its being applied to
5
Q
What’s the formula for pressure?
A
P= F/A
6
Q
What are the 2 types of wave motion?
A
Transverse & Longitudinal
7
Q
What is a transverse wave?
A
Vibration of particles is 90degress from direction of wave movement
8
Q
What is a longitudinal wave?
A
Vibration of particles is parallel to direction of wave movement
9
Q
Which wave is a sound wave?
A
Longitudinal
10
Q
What does longitudinal waves consist of?
A
Condensation & Refraction
11
Q
What is condensation?
A
Molecules are packed closely
There’s high pressure (+1)
12
Q
What is rarefaction?
A
Molecules pull away and due to elasticity and inertia it moves it past the molecule’s original point
-1
13
Q
What is a sine wave?
A
A pure tone sound wave that moves through a medium
14
Q
How is a wavelength measured?
A
It’s measured from any point on a sinusoid to same point on the next cycle of wave
15
Q
What is the formula of a wavelength?
A
W = v/f
16
Q
What happens as frequency increases?
A
Wavelength decreases
17
Q
A short wavelength has what type of frequency?
A
High
18
Q
A long wavelength has what type of frequency?
A
Low
19
Q
Frequency is perceived as…
A
Pitch
20
Q
Another way to identify frequency is…
A
By how many cycles occur over time
21
Q
What is the formula for frequency?
A
F = 1/t
22
Q
What is a period?
A
It’s the time to complete one cycle
23
Q
Period is the..
A
Inverse of frequency
24
Q
What is the formula for period?
A
T = 1/f
25
How does frequency effect mass?
Greater mass = lower frequency
26
How does frequency effect length?
Short length = higher frequency
27
How does frequency effect stiffness?
More compliant = lower frequency
More stiff = higher frequency
28
What is amplitude?
The distance the mass moves from the point of rest
29
Amplitude is perceived as...
Loudness
30
What is a complex sound?
It has a # of different frequencies and amplitudes
31
What is fundamental frequency?
The lowest rate of a sound's vibration
32
What are periodic sounds?
A complex sound that repeats over time
33
What is an aperiodic sound?
Complex sound that does not repeat over time.
34
Complex sounds consist of...
Periodic & Aperiodic sounds
35
What is a decibel?
It measures amplitude (pressure) or intensity(energy) of sound
36
What do we use decibels for?
The logarithmic scale. It compares an observed value to a standard or reference value
37
What is the standard reference?
Intensity = 10^-12 w/m^2
38
What is the effective standard reference?
0 dB
39
Is sound present @ 0dB?
Yes, because there's measured intensity or pressure
40
What is Observed Level?
Level of intensity or pressure that is measure or observed when a sound is present
41
For the observed level, what is being compared?
The value is compared to the reference level to get the decibel
42
What does a positive decibel mean?
There was MORE intense/higher pressure (Louder) than reference
43
What does a negative decibel mean?
There was LESS intense/lower pressure (Softer) than reference
44
What does a 0-value mean?
Means observed level is equal to reference
45
What is the pressure @ the reference level?
Pressure = 20 micro Pascals
46
What is the Intensity Level formula?
db(IL) = 10 x log (Io/Ir)
47
What is the Sound-Pressure Level (SPL) formula?
db(SPL) = 20 x log (Po/Pr)
48
Is Hearing Level the same as SPL?
No
49
What is Hearing Level?
It's a normative reference and is used for audiological purposes
50
For Hearing Level, since the human ear has different sensitivity at different frequencies, what occurs?
The different amounts of pressure (SPL) equate to 0HL @ each frequency
51
Define Threshold
It's the softest level at which a tone can be perceived 50% of the time
52
Define Sensation Level
of decibels a sound is above individual threshold
53
What's the formula for dB SL for finding threshold?
db SL = dbHL of presented sound - dB HL threshold
54
Define psychoacoustics
It's the study of relationship between physical stimuli (wavelength, amplitude) and the psychological response to the stimuli
55
When it comes to pitch, what does it deal with?
Highness vs Lowness
56
What is the human range of hearing?
20-20,000Hz
57
When it comes to loudness, what does it deal with?
Soft vs Loud
58
What does loudness relate to?
Intensity/Pressure
59
What is the relationship between our ears and frequency?
It is not equally sensitive to all frequencies
60
Define localization
It's the ability to tell which direction a sound is coming from
61
For localization to occur, what must it interact with?
Our ears, time, & intensity
62
Define reverberation
It's a reflected sound wave and incident sound waves interacting
63
What does reverberation cause?
It causes sound to be perceived as coming from a direction other than its source
64
What type of setting does not cause reverberation to occur?
Free field & Anechoic Chamber
65
What is another name for a sound wave?
Incident wave
66
What occurs once an incident wave is generated?
1. Transmission wave
2. Absorption wave
3. Reflection wave
67
What is a transmission wave?
A sound wave traveling through air w/o obstruction
68
What is an absorption wave?
Energy of sound wave is decreased (damped) due to friction from obstructing materials
69
What is a reflection wave?
An energy of a sound wave hits an obstruction and bounces back
70
What type of surface does a reflection wave bounce of?
A harder surface
71
What does the reflected sound wave do to our ears?
The reflected sound waves reach our ear slightly after the incident wave and this prolongs the sound
72
How can reverberation affect communication?
It can cause speech sounds to overlap and blend together
73
What is an echo?
A verrrrrrrrrrrrrrrrrrrrrrrrrrrrrry long delay when one hears two separate distinct sounds
74
Define impedance
It's a resistance to the transmission of acoustic energy
75
What type of material causes more impedance?
Denser material
76
Define masking
Two sounds being heard at the same time because of a change in threshold of sound A due to the introduction of sound B
77
Which sound is the masker?
Sound B
78
How does sound A become inaudible?
By sound B
79
What two types of sound measurements are audiologist interested in?
1. Hearing ability in patients (dB HL)
| 2. Sound pressure levels in the environment (dB SPL)
80
What is an audiometer?
Determines hearing sensitivity and to complete supra threshold testing
81
What does supra mean?
Testing above the threshold (aka Sensation Threshold)
82
What does an audiometer generate?
Pure tones of different frequencies from 125-12000 Hz
83
What does the audiometer typically test?
From 250-8000 Hz
84
On the audiometer, what else can be presented besides a pure tone?
1. Mic/live voice
2. CD/tape
3. Noise
4. Warble/Pulsed tone
85
What are transducers?
It's how sound from the audiometer gets into our ears
86
What are the transducers for Air Conduction?
1. Supra-aural
2. Circumaural
3. Inserts
4. Speakers
87
What is the transducer for Bone Conduction?
Bone Conduction oscillator (vibrator)
88
What is a sound level meter?
A device measuring what is perceived to the human ear
89
What is the sound-level meter important for?
Industrial settings & for background noise in testing situations
90
What is calibration?
Establishing the relationship between a measuring device and the units of measure
91
How can a calibration occur?
1. Daily biologic/listening check
| 2. Yearly calibration
