3030 Resonance and Filter characteristics

Free vibration

Object vibrates without interference at a rate that is determined by mass, tension, and stiffness

Natural/resonant frequency (RF)

rate at which an object vibrates freely

Forced vibration

Vibrations from one object can set another object into vibration if the RFs of both objects are reasonably close

Driving/applied frequency

wave that forces a resonator into vibration

The closer the RF of the driving force to the RF of the resonator, the ________ the amplitude of the response of the resonator

greater

Resonators do not ________ sound energy

initiate

Impedance

opposition to the flow of energy

Resistance

opposition caused by energy lost to particles interacting with one another (friction)

Reactance

opposition to the flow of an acoustic/mechanical vibration, usually due to inertia (mass or elasticity/stiffness)

In resonance, mass and stiffness are _______

equal

Mass and stiffness are ____ degrees out of phase with each other

180

If mass and stifness are equal, the only force acting on the vibration is ________

friction/resistance

Mechanical resonator

actual object itself is set into vibration

Acoustic resonator

container filled with air is set into vibration

* important for speech production

Smaller volumes of air resonate at ________ frequencies

higher

__________ volumes of air resonate at lower frequencies

Larger

Resonators ______ out some frequencies, while allowing others to remain

filter

A resonator ________ frequencies closet to tube's RF

amplifies and transmits

A resonator _________ frequencies that are farther away from tube's RF

dampens and prevents the transmission of

Bandwidth of a resonator

range of frequencies that it will transmit

_________ and _____________ of the container determine bandwidth of the resonator

Shape, physical characteristics

A sharply tuned resonator has a _________ bandwidth

narrow

A ________ tuned resonator has a greater bandwidth

broadly

Sharply tuned resonators tend to be _________

symmetrical

Broadly tuned resonators tend to be ________

irregular in shape

Cutoff frequency

point at which a resonator becomes unresponsive to an applied frequency, there is a marked reduction in intensity by 1/2

Upper cutoff frequency (Fu)

point at which there is a 3 dB decrease in amplitude of response than at center frequency (Fc)

Lower cutoff frequency (FI)

point at which there is a 3dB decrease in amplitude of response than at Fc

Attenuation rate/roll-off rate/slope

rate at which the resonator's amplitude is attenuated

A roll-off rate of 18 dB/ocatave would be

shallow

Given that a roll-off rate has a range between 18 and 48 dB/octave, what is the classification of the resonance curve?

Moderately steep

A roll-off rate greater than 90 dB/octave is

extremely steep

Low-pass filter

transmits acoustic energy BELOW a specific upper cutoff frequency

High-pass filter

transmits acoustic energy ABOVE a specific lower cutoff frequency

Band-pass filter

transmits acoustic energy in a particular range of frequencies

Band reject filter

Rejects all frequencies between two cut-off frequencies

Idealized and realized filters

Input intensity - Attenuation = ?

Output intensity

Uses of filters include:

Removing unwanted components in a signal, shaping the spectrum of a complex wave, and determining spectra of complex waves