Wavelength and Decibels Flashcards
What is another word for longitudinal waves?
Compression Waves
What is the peak called in a longitudinal wave?
compression
What are trough called in longitudinal waves?
rarefaction
What is a history plot?
a single particle or point along the medium that is vibrating / being disturbed over many times.
What is a snapshot?
A single time or moment for many points/ particles along the wave or medium.
Amplitude in transverse wave shows how much:
The material has been displaced from its equilibrium
(ex: water wave = how high the waves gets above the still water level)
Amplitude in longitudinal/compressional wave shows how much:
How much the pressure goes above and below the ‘‘normal ambient pressure’’ (ex: how much density increase increases of decreases from normal density)
What is T?
Period, how fast it takes a particle to complete one cycle (in s) 1/f
What is frequency?
The amount of cycles in 1 second f = 1/T (Hz)
What is λ?
Wavelength, the lengths between to repeated locations along the wave (in m)
What is the concept behind the motion of the green arrows?
It is the disturbance/wave that propagates
What is the concept behind the motion of the orange arrows?
Each single particles goes back and forth (oscillates) and collides with the next one
What is negative pressure?
Pressure below normal atmospheric pressure. Rarefaction of air particles
What is wave speed?
How quickly the disturbance travels along the medium. (in m/s)
What is the formula of wave speed?
v= λ/T or v= fλ
What are the 5 criteria on which a traveling through space depends?
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)
Explain what What does the X(t,z) represent in this equation?
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)
What does the A represent in this equation?
Amplitude (either in spatial, pressure, density,
What does the -+ represent in the equation?
The direction of the wave.
- means forward
+ means backward
What are the three characteristics that differentiate any two sounds from each other?
1) How loud
2) Pitch
3) Quality
Define loudness:
How loud a sound is.
Relates to Amplitude
A low amplitude sound is ___________
Quieter
A high amplitude sound is ___________
Louder
What unit do we use for loudness?
Decibels (β) dB
What are the two elements that we use to calculate Decibels?
Intensity βIL
Pressure βSPL
Intensity is _________________________ (Intensity βIL)
energy description of sound I=P/A P=E/t
Pressure is __________________________ (βSPL)
Force description of sound P=F/A
What is pitch?
Tone of a sound from frequency
High frequency =
High pitch
Low frequency =
Low pitch
What is the range of hearing?
It is the frequency range that specie can hear
What is the frequency range of humans?
20 Hz to 20000 Hz
Sounds below 20 Hz are called __________________
Infrasonic
Sounds above 20000 Hz are called____________________
Ultrasonic waves
What is quality?
Characteristic which enables us to distinguish one sound from another having the same pitch and loudness.
What is quality?
Characteristic which enables us to distinguish one sound from another having the same pitch and loudness.
Explain the fact that the perception loudness is not linear.
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.
Give a real life example of the Loudness rule of thumb.
It takes 10 violins to sound twice as loud as 1 violin
Why do we use logarithms? (2)
They make something nonlinear into something linear
They make powers of multiplication into addition processes
What reference do we use to assign the threshold value of 0 dB for both pressure and intensity?
The average baseline value which is the smallest intensity/pressure value we can hear. Pnaught or Inaught
Inaught =
Pnaught =
What is the logarithmic rule? (equation)
What is the formula of βIL?
What is the formula of βSPL?
What reference do we use to assign the threshold value of 120 dB for both pressure and intensity?
Pain threshold of humans for hearing
