Real-Time Plotting - 13.4.2 | 13. Real-Time Signal Processing using MATLAB | IT Workshop (Sci Lab/MATLAB)
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13.4.2 - Real-Time Plotting

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Interactive Audio Lesson

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Introduction to Real-Time Plotting

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Teacher
Teacher

Today, we will explore real-time plotting using MATLAB. Real-time plotting allows us to visualize audio signals instantaneously as they're recorded. Can anyone tell me why real-time visualization is important?

Student 1
Student 1

It helps us understand how the sound looks in a waveform form!

Teacher
Teacher

Exactly! It helps in analyzing the characteristics of the signal. We use the `plot()` function primarily. How do you think we would set up our audio recorder in MATLAB?

Student 2
Student 2

We can use `audiorecorder`!

Teacher
Teacher

Correct! And after recording, we can plot it. The basic command would be `plot(myRecording);`. Would anyone like to give it a try with a sample audio?

Interpreting Plots

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Teacher
Teacher

Now that we can plot the data, what do we actually see in these plots? When we look at the plot of an audio signal, what do the axes represent?

Student 3
Student 3

The x-axis shows the sample index, while the y-axis shows the amplitude of the sound wave.

Teacher
Teacher

Exactly! Proper labeling of these axes is crucial. What would we want to include in our plot for clarity?

Student 4
Student 4

We should add titles and labels to the axes!

Teacher
Teacher

Great! Using `xlabel()`, `ylabel()`, and `title()`, we can clarify our plot. If we call `xlabel('Sample Index')` and `ylabel('Amplitude')`, what do we communicate to the viewer?

Student 1
Student 1

It helps them understand what they are looking at in the plot.

Practical Application of Real-Time Plotting

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Teacher
Teacher

Let's try a short demonstration. Who can set up the recording code for us?

Student 2
Student 2

We can do `recObj = audiorecorder(44100, 16, 1);` and then `recordblocking(recObj, 5);` to get 5 seconds of audio.

Teacher
Teacher

Good job! And once we have the recording, what’s the next step?

Student 3
Student 3

We retrieve the audio data using `myRecording = getaudiodata(recObj);` and then plot it.

Teacher
Teacher

Exactly! Now let's visualize. After plotting, it's important to discuss what features we analyze from the wave. Can anyone think of features like peaks or troughs?

Introduction & Overview

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Quick Overview

This section covers how to perform real-time plotting of audio signals in MATLAB to visualize the amplitude over time.

Standard

In this section, we learn how to utilize MATLAB to plot real-time audio signals. The primary focus is on using the plot function to display the collected audio waveform, along with labeling the axes and providing meaningful titles to ensure clarity.

Detailed

Real-Time Plotting in MATLAB

Real-time plotting in MATLAB is crucial for visualizing signals as they are captured. The section begins by outlining the basic command needed to plot audio data captured by MATLAB's audiorecorder – specifically, the plot() function. By executing the command plot(myRecording);, we can instantly generate a visual representation of this audio data. The addition of labels and titles using xlabel(), ylabel(), and title() functions enhances the interpretability of the plot, framing the waveform in a clear context. This section emphasizes the importance of real-time visualization in signal processing, not only for analysis but for practical adjustments during live signal acquisition.

Audio Book

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Plotting the Audio Signal

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plot(myRecording);
title('Real-Time Audio Signal');
xlabel('Sample Index');
ylabel('Amplitude');

Detailed Explanation

In this step, we are using MATLAB's plotting functions to visualize the audio signal that has been recorded. The 'plot' function takes the variable 'myRecording', which contains the audio data, and creates a plot of the audio over time. The 'title' function sets the title of the plot, stating it's a real-time audio signal. The 'xlabel' and 'ylabel' functions label the axes; 'Sample Index' on the x-axis represents each sample point in the data, while 'Amplitude' on the y-axis shows the strength or intensity of the audio signal at those sample points.

Examples & Analogies

Think of plotting the audio signal like displaying a heartbeat on a monitor in a hospital. Each spike represents the heart's activity over time. Similarly, each point in the plotted audio signal represents the sound at a specific moment, allowing us to visualize how the sound changes.

Understanding the Axes of the Plot

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xlabel('Sample Index');
ylabel('Amplitude');

Detailed Explanation

The x-axis labeled 'Sample Index' indicates each individual audio sample taken during recording. Each sample represents a tiny fraction of time, showing the specific value of the audio signal at that moment. The y-axis labeled 'Amplitude' represents how

Examples & Analogies

No real-life example available.

Definitions & Key Concepts

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Key Concepts

  • Real-Time Plotting: The process of visualizing signals as they are produced, allowing for immediate analysis.

  • audiorecorder object: A MATLAB tool used for capturing audio input.

  • plot function: A MATLAB command used to create a graphical representation of data.

  • Amplitude: The strength of the audio signal, represented visually in a plot.

Examples & Real-Life Applications

See how the concepts apply in real-world scenarios to understand their practical implications.

Examples

  • Using the command plot(myRecording); to visualize an audio signal after recording.

  • Labeling the axes with xlabel('Sample Index') and ylabel('Amplitude') for clarity in the plot.

Memory Aids

Use mnemonics, acronyms, or visual cues to help remember key information more easily.

🎵 Rhymes Time

  • To plot and see, use plot with glee, amplitude and time, in harmony!

📖 Fascinating Stories

  • Imagine capturing sound in a jar (audiorecorder), and looking inside (plot) to see how the sound was shaped—tall and short waves tell if it's loud or soft.

🧠 Other Memory Gems

  • P.A.T: Plot, Amplitude, Time - Remember how to analyze audio signals.

🎯 Super Acronyms

A.P.S

  • Amplitude
  • Plot
  • Sample - Key elements in audio signal visualization.

Flash Cards

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Glossary of Terms

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  • Term: RealTime Plotting

    Definition:

    The capability to visualize data or signals as they are being recorded or processed.

  • Term: audiorecorder

    Definition:

    A MATLAB object that records audio data from an input device.

  • Term: plot

    Definition:

    A MATLAB function used to create a graph of data points in 2D.

  • Term: Amplitude

    Definition:

    The height of the wave; represents the intensity of the sound.

  • Term: Sample Index

    Definition:

    The discrete time points at which the amplitude of the signal is measured.