Wavelength and Decibels

Question 1

What is another word for longitudinal waves?

Answer 1

Compression Waves

Question 2

What is the peak called in a longitudinal wave?

Answer 2

compression

Question 3

What are trough called in longitudinal waves?

Answer 3

rarefaction

Question 4

What is a history plot?

Answer 4

a single particle or point along the medium that is vibrating / being disturbed over many times.

Question 5

What is a snapshot?

Answer 5

A single time or moment for many points/ particles along the wave or medium.

Question 6

Amplitude in transverse wave shows how much:

Answer 6

The material has been displaced from its equilibrium
(ex: water wave = how high the waves gets above the still water level)

Question 7

Amplitude in longitudinal/compressional wave shows how much:

Answer 7

How much the pressure goes above and below the ‘‘normal ambient pressure’’ (ex: how much density increase increases of decreases from normal density)

Question 8

What is T?

Answer 8

Period, how fast it takes a particle to complete one cycle (in s) 1/f

Question 9

What is frequency?

Answer 9

The amount of cycles in 1 second f = 1/T (Hz)

Question 10

What is λ?

Answer 10

Wavelength, the lengths between to repeated locations along the wave (in m)

Question 11

What is the concept behind the motion of the green arrows?

Answer 11

It is the disturbance/wave that propagates

Question 12

What is the concept behind the motion of the orange arrows?

Answer 12

Each single particles goes back and forth (oscillates) and collides with the next one

Question 13

What is negative pressure?

Answer 13

Pressure below normal atmospheric pressure. Rarefaction of air particles

Question 14

What is wave speed?

Answer 14

How quickly the disturbance travels along the medium. (in m/s)

Question 15

What is the formula of wave speed?

Answer 15

v= λ/T or v= fλ

Question 16

What are the 5 criteria on which a traveling through space depends?

Answer 16

1) Transverse or Longitudinal/compression wave
2) Density of the material (↓ρ means ↑v)
3) Elasticity of the material (↑stiffness means ↑v)
4) Temperature (↑Temp means ↑v)
5) State of matter (gasses → liquid →solid)

Question 17

Explain what What does the X(t,z) represent in this equation?

Answer 17

This is a two-dimensional function which depends on two independent variables. Where is X depending on t= time (s) z= location along the material (m)

Question 18

What does the A represent in this equation?

Answer 18

Amplitude (either in spatial, pressure, density,

Question 19

What does the -+ represent in the equation?

Answer 19

The direction of the wave.
- means forward
+ means backward

Question 20

What are the three characteristics that differentiate any two sounds from each other?

Answer 20

1) How loud
2) Pitch
3) Quality

Question 21

Define loudness:

Answer 21

How loud a sound is.
Relates to Amplitude

Question 22

A low amplitude sound is ___________

Answer 22

Quieter

Question 23

A high amplitude sound is ___________

Answer 23

Louder

Question 24

What unit do we use for loudness?

Answer 24

Decibels (β) dB

Question 25

What are the two elements that we use to calculate Decibels?

Answer 25

Intensity βIL
Pressure βSPL

Question 26

Intensity is _________________________ (Intensity βIL)

Answer 26

energy description of sound I=P/A P=E/t

Question 27

Pressure is __________________________ (βSPL)

Answer 27

Force description of sound P=F/A

Question 28

What is pitch?

Answer 28

Tone of a sound from frequency

Question 29

High frequency =

Answer 29

High pitch

Question 30

Low frequency =

Answer 30

Low pitch

Question 31

What is the range of hearing?

Answer 31

It is the frequency range that specie can hear

Question 32

What is the frequency range of humans?

Answer 32

20 Hz to 20000 Hz

Question 33

Sounds below 20 Hz are called __________________

Answer 33

Infrasonic

Question 34

Sounds above 20000 Hz are called____________________

Answer 34

Ultrasonic waves

Question 35

What is quality?

Answer 35

Characteristic which enables us to distinguish one sound from another having the same pitch and loudness.

Question 35

What is quality?

Answer 35

Characteristic which enables us to distinguish one sound from another having the same pitch and loudness.

Question 36

Explain the fact that the perception loudness is not linear.

Answer 36

Loudness is the strength of the ear’s perception of the sound. The rule of thumb for loudness is that is doubled only when the intensity is increase by ten.

Question 37

Give a real life example of the Loudness rule of thumb.

Answer 37

It takes 10 violins to sound twice as loud as 1 violin

Question 38

Why do we use logarithms? (2)

Answer 38

They make something nonlinear into something linear
They make powers of multiplication into addition processes

Question 39

What reference do we use to assign the threshold value of 0 dB for both pressure and intensity?

Answer 39

The average baseline value which is the smallest intensity/pressure value we can hear. Pnaught or Inaught

Question 40

Inaught =

Answer 40

Question 41

Pnaught =

Answer 41

Question 42

What is the logarithmic rule? (equation)

Answer 42

Question 43

What is the formula of βIL?

Answer 43

Question 44

What is the formula of βSPL?

Answer 44

Question 45

What reference do we use to assign the threshold value of 120 dB for both pressure and intensity?

Answer 45

Pain threshold of humans for hearing