resonance & tube models - exam 1 Flashcards
resonant frequencies
frequencies at which the vocal tract naturally amplifies sound waves
formants
specific resonant frequencies of the vocal tract that shape the acoustic properties of vowels & other speech sounds
what does F1 relate to
the height of the tongue
what does the F2 relate to
advancement of the tongue
what happens when a compression wave reflects on the closed end of a tube
it is reflected back as a compression wave
what happens when a compression wave reflects off the open end of a tube
it is reflected back as a rarefaction wave
standing waves
sound waves in a tube interacting & combining with incoming waves
forms consistent peaks & valleys
single tube model
models the vocal tract as a single tube
ideal for understanding basic vowel production
multi tube model
represents the vocal tract as a series of connected tubes
entire length is fixed, but can adjust each section
(front gets longer –> back gets shorter)
resonance in a closed tube
- 1st peak enters tube
- 1st peak reaches halfway point
- 1st peak reaches end & reflects
1st trough enters tube - reflected peak reaches halfway point
1st trough reaches halfway point - reflected peak reaches speaker again
1st trough reaches the end & reflectes
2nd peak enters tube
what is the pressure in the middle of a closed tube
always zero - the waves are cancelling each other out
particles are moving the most
where is pressure zero in a closed-open tube
at the open end
helmholtz resonator
model of sound resonance in a cavity w/ a narrow opening (like vocal tract)
crucial in shaping low-freq sounds
glass bottle shape - large closed back cavity
small closed open front cavity
how to calculate resonant freqs in closed tube
fn = nc/2L
n = the freq number
c = the speed of sound (35000)
L = length of the tube
how to calculate resonance for a closed open tube
fn = (2n-1)c / 4L
(2n-1) = odd numbers
1 = 1
2 = 3
3 = 5
4 = 7
source & filter are dependent
formants do not depend on harmonics
envelope
broad shape of the wave
peaks = formants
are formants equally spaced
no
2 closed open tubes
skinny tube in the larynx = back cavity
- closed-open
fat tube in the mouth = front cavity
-closed-open
(technically open where glottis connects, but opening so small it doesn’t really matter)
can we set L the length of a complex tube
no
sound waves travel differently in different sized tubes so they need to be measured separately
as a cavity lengthens, the frequencies get…?
lower
why do shorter cavities have higher freqs
shorter tube takes less time to reflect
want to put energy in more often
more often = more frequent = higher frequency
higher frequency = higher pitch
how to find formants on a nomogram
lowest resonance on graph = F1
second lowest = F2
third lowest = F3
which tube contributes the formants
the longer one
longer = lower
i am sitting in a room - what was it
same recording played over & over again in a room
eventually sound distorted into resonant hums
i am sitting in a room - why
the resonant freqs of the room kept amplifying each other
