Module 7 Resonance and Filtering

sound waves produced by the vocal folds will be altered by a process called _____ and _____ to produce various vowels

resonance

filtering

the principle of resonance

when a periodic force is applied to an elastic system, the system is forced to vibrate at the frequency of the applied force, not at f_nat of the elastic system

the closer the frequency of the applied force to the natural frequency of the system, the greater the amplitude of vibration

natural frequency of middle ear

2000 Hz

greatest amplitude happens at ____ of the elastic system

f_nat

the more remote from the natural frequency….

the more amplitude decreases

what does 0 dB mean on this graph?

500 Hz

what does 0 dB mean on this graph?

level of harmonics with greatest amplitude

does A or B represent a complex tone?

B

at the input, amplitudes are _____, but in the output, amplitudes _____ with _______

do these graphs show the input or the output?

constant

vary, frequency

output

list a characteristic of these graphs make them different

B shows a complex tone

A shows a pure tone

this is NOT a _____ but a ______

sound wave

frequency-selective system

what does this graph show?

it shows the relative amplitude of forced vibrations as a function of frequency that would be realized if driving forces of variable frequency, but constant amplitude, were applied

what are the names of this curve?

resonance curve

filter curve

system transfer function

amplitude response

frequency response

Answer the questions on the graph.

Impedance is minimal

Admittance is maximal

_____ and _______ of the elastic system determines its natural, or resonant frequency

mass

stiffness

elastic system is forced to vibrate at…

frequency of the applied force

amplitude of vibration of elastic system is greatest when the _____ _______ equals the ______ ________ of the system

driving frequency

natural frequency

stiff and light objects

vibrate rapidly and produce high-frequency sound waves

heavy objects

vibrate slowly and produce low-frequency sounds

if there is less resistance to the vibration of motion

then it may continue vibrating for some time before the energy is dissipated

if there is more resistance to the vibration of motion

then the oscillation will be brief, and the energy will dissipate quickly

harmonics above and below the center are attenuated because _______ increases

impedance

parameters of a filter

center frequency (F_c)

upper cutoff frequency (F_L)

lower cutoff frequency (F_U)

bandwidth (BW or ΔF)

attenuation rate

center frequency

maximum amplitude of vibration, the natural frequency

upper cutoff frequency

that frequency above f_c for which amplitude of response is 3 dB less than response at F_c

the 3 dB down point, or the half power point

lower cutoff frequency

that frequency below F_c for which amplitude of response is 3 dB less than response at F_c

the 3 dB down point, or half-power point

why is it called the half-power point

10log(1/2) = -3 dB

bandwidth

the width of the passband of the system, the range of frequencies passed by the filter

ΔF = F_U - F_L

quantifies how narrowly or broadly tuned the filter is

attenuation rate

the rate at which energy for frequency above or below the center frequency are rejected

reported in dB/octave

slope of the filter curve

also known as the roll-off or rejection rate

change in filter curve should be…

slow

attenuation rate quantifies the _____ of a filter

selectivity or energy concentration

when we specify parameters of a real filter, we describe it as if it were an ____ filter

idealized

specification of attenuation rate reveals how much _____ filter departs from the _____ one

realized

idealized

the idealized filter is in the shape of a…

rectangle

types of filter

low-pass

high-pass

band-pass

stop-band

low-pass filter

allows low frequencies through and attenuates high frequencies

above cutoff frequency, frequency components are attenuated

high-pass filter

allows high-frequencies through and attenuates low-frequencies

below cutoff frequency, frequency components are attenuated

band-pass filter

allows limited range of frequencies to pass through

has a low cutoff and high cutoff, bandwidth, and center frequency

stop band filter

opposite of bandpass filter

attenuates range of frequencies

filter skirts

determines the attenuation of frequency components outside the pass band, usually reported in dB per octave

there is/is not a perfect filter

there is not a perfect filter

what are the two values of attenuation are commonly used

3 dB and 10 dB

Q of a filter

center frequency/BW

high Q filter

sharply tuned filter

low Q filter

broad tuning filter

Equivalent Rectangular Bandwidth Filter

approximation of bandwidths of the filter in human hearing

bandwidth of a rectangular filter with the same peak output and same area as that filter

impulse/click/transient signals _____ and ______ response can be altered when they are passed through a _______ filter

temporal, frequency

band-pass

wide bandwidth of filter, broader spectrum, _____ impulse response

briefer

narrower bandwidth, steeper filter skirts, ____ duration of impulse response

greater

the longer you present a sound, the _____ the response

better