Please follow along with the video and create your own version of the comb filter in LabVIEW.
Refer to
TripleDisplay to install the
front-panel indicator used to view the signal spectrum.
[video] Implementing the comb filter in LabVIEW; exploration of the impulse response as a function of delay line length and feedback gain
Loop time and reverb time
As you have learned in previous sections, the comb filter behavior is determined by the delay line length N and the feedback coefficient g. From
a user's point of view, however, these two parameters are not very intuitive. Instead, the comb filter behavior is normally specified by
loop time
and
reverb time denoted
. Reverb time may also be written as
. Loop time indicates the amount of time necessary for a given sample to pass through the delay line, and is therefore the delay line length N times the
sampling interval. The sampling interval is the reciprocal of sampling frequency, so the loop time may be expressed as in
:
Reverb time indicates the amount of time required for the reverberant signal's intensity to drop by 60 dB (dB = decibels), effectively to silence.
Recall from the
video that the comb filter's impulse response looks like a series of decaying impulses spaced by a delay
of N samples; this impulse response is plotted in
with the independent axis measured in time rather than
samples.
Comb filter impulse response
Take a few minutes to derive an equation for the comb filter feedback gain "g" as a function of the loop time and the reverb time. The following
pair of exercises guide you through the derivation.
Given the comb filter impulse response pictured in
, derive an
equation for the reverb time
in terms of the loop time
and the comb filter's feedback constant g. Hint: Recall the basic equation to express the ratio of two amplitudes in decibels, i.e., use the form with a factor of 20.
Based on your previous derivation, develop an equation for the comb filter gain "g" in terms of the desired loop time
and reverb time.
To finish up, derive the equation for the comb filter delay "N" in terms of the desired loop time.
Now, return to your own comb filter VI and modify the front-panel controls and LabVIEW MathScript node to use loop time and reverb time as the primary user inputs.
Experiment with your modified system to ensure that the spacing between impulses does indeed match the specified loop time, and that the impulse decay rate makessense for the specified reverb time.
Comb filter implementation for audio signals
In this section, learn how to build a comb filter in LabVIEW that can process an audio signal,
specifically, an impulse source. Follow along with the
screencast video
to create your own VI. The video includes anaudio demonstration of the finished result. As a bonus, the video also explains where
the "comb filter" gets its name.
[video] Building a LabVIEW VI of a comb filter that can process an audio signal
Next, learn how you can replace the impulse source with an audio .wav file. Speech makes a good test signal, and
the
screencast video shows how to modify your
VI to use a .wav audio file as the signal source. The speech clip used as an example in the video is availablehere:
speech.wav (audio courtesy of the Open Speech Repository,
www.voiptroubleshooter.com/open_speech ; the sentences are two of the many phonetically balanced
Harvard Sentences , an important standard
for the speech processing community).
[video] Modifying the LabVIEW VI of a comb filter to process a .wav audio signal
References
Moore, F.R., "Elements of Computer Music," Prentice-Hall, 1990, ISBN 0-13-252552-6.
Dodge, C., and T.A. Jerse, "Computer Music: Synthesis, Composition, and Performance," 2nd ed., Schirmer Books, 1997,
ISBN 0-02-864682-7.
Questions & Answers
A golfer on a fairway is 70 m away from the green, which sits below the level of the fairway by 20 m. If the golfer hits the ball at an angle of 40° with an initial speed of 20 m/s, how close to the green does she come?
A mouse of mass 200 g falls 100 m down a vertical mine shaft and lands at the bottom with a speed of 8.0 m/s. During its fall, how much work is done on the mouse by air resistance
Chemistry is a branch of science that deals with the study of matter,it composition,it structure and the changes it undergoes
Adjei
please, I'm a physics student and I need help in physics
Adjanou
chemistry could also be understood like the sexual attraction/repulsion of the male and female elements. the reaction varies depending on the energy differences of each given gender. + masculine -female.
Pedro
A ball is thrown straight up.it passes a 2.0m high window 7.50 m off the ground on it path up and takes 1.30 s to go past the window.what was the ball initial velocity
2. A sled plus passenger with total mass 50 kg is pulled 20 m across the snow (0.20) at constant velocity by a force directed 25° above the horizontal. Calculate (a) the work of the applied force, (b) the work of friction, and (c) the total work.
you have been hired as an espert witness in a court case involving an automobile accident. the accident involved car A of mass 1500kg which crashed into stationary car B of mass 1100kg. the driver of car A applied his brakes 15 m before he skidded and crashed into car B. after the collision, car A s
can someone explain to me, an ignorant high school student, why the trend of the graph doesn't follow the fact that the higher frequency a sound wave is, the more power it is, hence, making me think the phons output would follow this general trend?
Nevermind i just realied that the graph is the phons output for a person with normal hearing and not just the phons output of the sound waves power, I should read the entire thing next time
Joseph
Follow up question, does anyone know where I can find a graph that accuretly depicts the actual relative "power" output of sound over its frequency instead of just humans hearing
Joseph
"Generation of electrical energy from sound energy | IEEE Conference Publication | IEEE Xplore" ***ieeexplore.ieee.org/document/7150687?reload=true
A string is 3.00 m long with a mass of 5.00 g. The string is held taut with a tension of 500.00 N applied to the string. A pulse is sent down the string. How long does it take the pulse to travel the 3.00 m of the string?
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Source:
OpenStax, Musical signal processing with labview -- sound spatialization and reverberation. OpenStax CNX. Nov 07, 2007 Download for free at http://cnx.org/content/col10485/1.1
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