Lecture (2/13) Week 5 Tuesday Flashcards
Air molecules do not linearly move to transmit the sound energy, they….
pass energy on from one molecule onto another
Dampening definition
gradual decrease in amplitude due to friction
describe a lossless system
sound goes on forever
describe a low-dampened system
sound echos, takes longer to dampen
describe a high-dampened system
sound is absorbed, quicker to dampen
definition of impedance
opposition that energy encounters when it is transferred from its source to a load
because sound waves constantly encounter barriers in their travel, this results in a change in
impedance
T/F impedance is a vector
true
The two components of impedance are
reactance and resistance
reactance=
mass and elasticity
resistance=
friction
What four things can happen when a change of impedance occurs?
-transmission
-reflection
-absorption
-diffraction
Transmission definition
amount of energy that successfully travels from the source to the load
For energy to be transferred, the impedance of the source must be _________ to the impedance of the load
similiar
What is the equation for transmission?
H=4ZbZa/(Zb+Za)2
H= proportion of energy transmitted
Za=impedance of medium a (source)
Zb= impedance of medium b (load)
What is reflection?
The amount of energy not transferred from the source to the load (or medium to medium)
What is the equation for reflection?
1.0-H= amount of sound reflected
What are the two waves of reflection?
-incident wave (original wave)
-reflective wave (energy that bounces back)
The reflective wave is always at the same _____ as the incident wave
angle
The reflected waves travels at the ____ ____ as the original wave
same speed
The angles of reflected ray to the perpendicular…
equal the angles of the incident rays to the perpendicular
Definition of echo
time delay between the reflective waves and the incident wave
Definition of reverberation
-delay between incident wave and reflective wave that is not detected by ear
-time it takes for a sound to decay to .001 of its original amplitude
-time it takes, in seconds, for a sound to decrease 60dB
Long reverberation time
higher number of seconds
-space with reflected surfaces (live room)
short reverberation time
fewer seconds
-space with absorptive surfaces (dead room)
anechoic chambers
soundproof rooms
(no reverberation)
an object will vibrate with the ____ _____ at its natural frequency
greatest amplitude
as you move away from the natural frequency, the _____ lessens
amplitude
the increased amplitude at the natural frequency can actually be ____ _____ than the sound that was introduced
more intense
Definition or resonators and filters
change or shape sound
-filters that alter the output of the sound
what are the 4 types of filters?
low pass
high pass
band with
band reject
Definition of a low pass filter
low frequencies get through and high frequencies get cut off
-gradual decrease of high frequencies
Cut off frequency of a low-pass filter or high pass filter
frequency at -3dB
How do you find the attenuation rate?
how many dB are attenuated per octave (doubling of frequency)
What does a low-pass frequency slope look like
negative slope
Definition of high pass filter
high frequencies get through and low frequencies get cut off
-gradual decrease of low frequencies
What does the slope of a high pass filter look like?
positive slope
Definition of band pass filter
band of frequencies get through
-both high frequencies and low frequencies get rejected
bandpass filter and band reject filter have ____ cut off frequencies
2
-one at the low end and one at the high end
bandwidth of a bandpass filter or band reject filter is
F1-F2 or F high- F low
definition of a band reject/ notch filter
all frequencies get through except a band
