Unit One Flashcards
In order to have sound what do you need to have?
A medium
What is sound?
A disturbance of particles in a medium
What is vibratory motion?
the back and forth motion of an object about its rest position
What is another name for simple vibratory motion
simple harmonic motion (SHM)
What is the equation for period?
Period = 1/frequency
What is the equation for frequency?
Frequency = 1/period
What does this formula mean?
Z = [R^2 + (Xm -Xs)^2]^1/2
Z = impedence
R= resistence
Xm = mass
Xs = stiffness
What is occuring at these spots?
Nodes
What is an antinode?
When there is constructive interference and waves are in phase sound occurs here
Antinodes have compression and rarefraction
What is a node?
Where there is destructive interference and two standing waves meet in phase opposition. Sound does not occur here
What is occuring at these spots?
antinodes
What is compression?
areas of increased particle density (air pressure)
For hearing this moves the tympanic membrane inward
What is rarefraction?
the equalizing aor decrease of particle density (air)
For hearing: this moves the tympanic membrane back out (to the original state) which equalizes pressure in the ear
What is normal air pressure (at sea level)?
14.7 lb/in^2
or
100,000 Pa
What is the equation of wavelength and what do the symbols mean?
wavelength (lamda) = c/frequency
lamda = wavelength
c = speed of sound in air
What is the speed of sound in air?
1130 ft/second
344 meters/second
What is the equation for natural resonant frequency (NRF)?
NRF = speed of sound/ (4L)
NRF = natural resonant frequency
L = length
What are the four things that can happen when sound waves encounter obsticles in the environment?
Transmission
Reflection
Defraction
Absorbtion
What is transmission?
When there is an impedence match (ie moving from air to air or water to water), the sound can travel thorugh the medium, the mediums are the same
What is Reflection?
What is an example of relection?
There is an impedence mismatch and soudn doesnt travel through. The greater the impedence mismatch the greater the reflection.
Walls in a classroom
What is defraction?
When the wave bends around the object. The object has to be 1/2 of the wavelength in order for it to defract.
What is Absorbtion?
What is it called acoustically?
What is an example?
When sound is absorbed into an object and dissipated or changed into heat energy. The greater the surface area the greater teh absorbtion. Also the more pourous the material the more absorbtion
Acoustically this is called dampening
An anechoic chamber
What is the equation of the inverse square law?
Inverse Square Law = Intensity = power/ 4pr^2
p = pressure
r = distance between you and the source
pressure = force/d^2
When is this formula used?
Wavelength (lamda) = c/f
When you want to calculate the wavelength
When is this equation used?
c/4(L)
when finding the Natural Resonant Frequency (resoncance of a tube closed at one end)
explains the influence of distance on the magnitude of speed as it travels from its source
How would you explain 80 dB to a novice
it is 10,000 times the human threshold
How would you describe -20 dB to a novice?
it is 100 times lower than the human threshold
What is the logatrithms chart for decibles?
What is the SPL equation?
SPL = 20 x Log10 (Po/ Pref)
SPL = sound pressure level which is the average level for a 1 KHz tone
Po = observed soudn pressure
Pref = 0.00002 Pa
What is the Pref for the SPL equation?
0.00002 Pa
What are the Sound Environments?
Sound Field
Reberverent Field
Anechoic Chamber
Free Field
What is a sound field?
What is an example of a sound field?
there are better thresholds here
example: when getting a hearing test
What is a Reberverent Field?
where a sound is refected back (echos) and this tells you how big a room is, this is a normal field
What is reverberation time?
the time it takes for sound to come back to you
1/1000
20x log (ratio)
- 60 dB
What is a free field:
Where nothing is reflected back at you
Example of this is space
What is an Anechoic Chamber
All soudns are absorbed here and turned to heat
Anechoic Chamber called a tourchure chamber
What do you need to have for a sound?
vibration (body cabable of vibrating)
Medium (this is set into motion)
an energy source
There needs to be a disturbance of particles in a medium
What do you experience or percieve in a sounds?
intensity (amplitude or loudness)
frequency (pitch)
phase (locaiton form Right to Left ear)
What does Fourier’s analysis measure?
Intensity
Frequency
Phase
What does SPL stand for?
Sound Pressure Level
the average threshold for a 1 KHz tone
What is HL?
hearing level
the average threshold for a specific audiometric tones
audiologists use this
What is SL?
sensation level
particular threshold for any sound listener
What is displayed by a speech spectrograph
Speech spectrograph is a slice by slice over time look
measures:
intensity (which is in terms of darkness)
frequency (pitch)
period
What has node and antinodes in fixed spacial positions?
A standing wave
What difference is there in the spectra of noise vs. tones?
Noise = random and peridoic, can’t be repeated and diferent form one moment to the next
Tones = pure tones and complex tones -> they are periodic and can be repeated
What type of graph is noise drawn on?
A continuous line spectrum
What type of graph are tones drawn on?
Line Spectrum
energy in discrete intregals
