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SPA 3030 > Module 7B: Filters > Flashcards

Module 7B: Filters Flashcards

1
Q

Review:

Every object has one frequency at white it vibrates with the greatest ease is known as?

A

Resonance

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2
Q

Review: The farther the frequency is from the resonant frequency, the lower the amplitude of vibration (loudness decreases)

True or false

A

True

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3
Q

Every object attenuates energy at some frequency and allows energy at other frequencies to pass through. This means that every object is a ?

A

FILTER

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4
Q

Look at picture in Exam 3 folder labeled: filter Curve

A

We show how much sound will be attenuated on FILTER CUVE( what you are looking at). The frequency is on the x axis and the relative amplitude ( is the amount of attenuation) is shown on the y-axis. If we want to see how much any particular frequency will be attenuated by the filter, we simply find the frequency on the x axis and go up on the filter curve. The heigh of the filter curve at the frequency , is the relative amplitude of the sound after it leaves the filter. So if we had a sound at this frequency , it will be reduced in amplitude by 10 db after it leaves the filter. The sound above the filter curve will be blocked by the filter. Everything below the curve will be allowed to pass through, but it will be attenuated by the amount indiciated by the curve.

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5
Q

Just like your coffee, an acoustic filter acts similarily. Which sounds get blocked and which sounds get through is determined by FIVE PARAMETERS. NAME THEM.

A 
Center frequency
upper cutoff frequency
lower cutoff frequency
bandwidth 
attenuation rate
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6
Q

What is the frequency with the least amount of attenuation?

A

The center frequency. (fc)

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7
Q

At the center frequency, there is very little ____ to the transfer of energy.

Impedance increases as you move away from the center frequency of a filter. T/F

A

impedance

true

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8
Q

What is the point at which the filter is attenuating by 3 db

A

the cutoff frequency

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9
Q

The frequency above the center frequency in which amplitude of response is 3dB less than the response at the center frequency.

A

Upper cutoff frequency

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10
Q

Remember, halving the intensity of a sound decreases the amplitude of the sound by three decibles; Thus the cutoff frequencies halve the intensity of the sound at that frequency.

A

** just know this**

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11
Q

attentuate means?

A

Reducing

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12
Q

What is the frequency below the the center frequency for which amplitude of response is 3 dB less than response at center frequency ?

Frequncies below this point are attenuated

A

lower cutoff frequency

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13
Q

What defines the range of frequencies allowed to pass relatively unchanged by the filer

A

bandwith

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14
Q

Bandwidth quantifies ?

a) The amount of resonance allowed to pass
b) The total lower cutoff + the uppercut off
c) How narrowly or broadly tuned the filter is
d) How unchanged the filter is after i3 db removed from the center frequency

A

C:How narrowly or broadly tuned the filter is

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15
Q

BW=Fu-FL

Bandwidth formula

A

=D

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16
Q

In a perfect world, a filter would only allow frequencies between the lower cutoff frequency and the upper cutoff frequency to pass through and not attenuate sound between the cutoff frequencies Why is this not possible?

Look at image”ideal “

A

This is not possible without introducing distortion into the signal. And since the purpose of a filter is to remove unwanted sound energy, adding more in through distortion would defeat the purpose of a filter.

17
Q

In reality, a filter gradually increases:

a) The amount of sound above 3db
b) The amount of unwanted sound energy + the cutoff energy
c) the amount of attenuation applied to frequencies as they get closer inside the cutoff frequencies
d) the amount of attenuation applied to frequencies as they get further outside the cutoff frequencies

A

d) the amount of attenuation applied to frequencies as they get further outside the cutoff frequencies

18
Q

This gradual increase in attenuation is the attenuate rate –aka the ____.

A

Slope of the filter

19
Q

Attenuation rate can be referred as all of these except:

  • Slope
  • rejection width
  • rejection rate
  • roll-off rate
A

-rejection width

20
Q

What is the rate at which energy for frequencies less than the FC or greater than the FC are rejected?

A

Attenuation rate

Measured in dB per octave

21
Q

Look at the attenuation rate picture . What is the attnuation rate of the left side of filter A? Calculate by determining the difference in attenuation of 500 and 100 HZ.

A is the color in green

A

Answer=10dB

22
Q

The attenuation rate quantifies the :

A) the cutoff frequency of a filter

b) the Relative amplitude of a filter
c) Selectivity of a filter
d) vibration levels of a filter

A

c) selectivity of a filter

23
Q

A filter with high attenuation rate is said to be?

A

highly selective

24
Q

The gentler the slope, the less likely to introduce distortion. True or false.

A

True

25
Q

Which of the following is true of the slope of a filter?

a) the steeper the slope, the less likely it is that distortion will be added to the signal
b) it is the point at which the intensity of the input signal is cut in half
c) it is the number of decibels that the attenuation changes over an octave
d) it misdefines as the distance between the upper and lower cutoff frequencies.

A

c) it is the number of decibels that the attenuation changes over an octave

26
Q

What is someone referring to if they say a filter is being broadly or narrowly tuned:

a) the attenuate rate
b) the bandwidth
c) the center frequency

A

b) the bandwidth

27
Q

Which of the following best defines an upper cutoff frequency?

a) is the rate at which frequencies that are higher are attenuated
b) allows lower frequencies to pass relatively unattenuated
c) allows higher frequencies to pass relatively unattenuated
d) is the rate at which frequencies that are lower are attenuated

A

b) allows lower frequencies to pass relatively unattenuated

28
Q

Impedance is minimal at center frequency and admittance is maximal at center frequency. True or false

A

True

SPA 3030 (11 decks)

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