Lab 5: Smooth Signal

Task Outline

• Due Date: Friday, November 1, 2019
• Total Points: 10
• Implement a Java program that smoothes an audio signal by averaging an array of integers.

Background Theory

• An audio signal is sometimes stored as an array of integer values. The values represent the intensity of the signal at successive time intervals. Of course, in a program, the signal is represented with an array.
• Often, a small amount of noise is included in the signal. Noise is usually small, momentary changes in the signal level. An example is the static that is heard in addition to the signal in AM radio.
• Smoothing a signal removes some of the noise, and improves the perceptual quality of the signal. This assignment requires you to smooth the values in an array of integers.

Hints

• First, you should create a result array called smooth, which has exactly the same size as the audio array.
• The first element of the smooth array is a special case, because it should be calculated from the average of the first two elements of the audio array.
• The last element of the smooth array is also a special case, because it should be calculated from the average of the last two elments of the audio array.
• The internal elements of the smooth array can be calculated from a for loop in the following manner. First, you will need to determine the boundaries of this loop. You should probably begin at index 1, and go up to index audio.length-1.
• Then, you will need to calculate the average of three elements in the audio array, for every index i. In other words, you will need to calculate the average of the three values: audio[i-1], audio[i], and audio[i+1].

Code Distribution

Description	File Size	File Name
Java Source Code for Smooth Signal	6.2KB	lab05.zip

Contents of lab05.zip:

Lab05SmoothSignal/
├── package.bluej
├── README.TXT
├── SmoothSignal.class
├── SmoothSignal.ctxt
├── SmoothSignal.java
├── SmoothSignalJUnitTest.class
├── SmoothSignalJUnitTest.ctxt
└── SmoothSignalJUnitTest.java

Specification

• Write a Java program in the file SmoothSignal.java that smoothes an audio signal by averaging an array of integers.
• You will write your solution in a function called levelling(int[] audio) right below the place where it says: YOUR CODE HERE
• When the function call levelling([1, 5, 4, 5, 7, 6, 8, 6, 5, 4, 5, 4]) is executed, the output of the program should be: [3 3 4 5 6 7 6 6 5 4 4 4 ]

Testing

• Click on the Run Tests button to execute the JUnit test bench. JUnit indicates a successful test with a green bar, and an unsuccessful test with a red bar.

Submission

• Upload the file SmoothSignal.py to the Web-CAT automated grading platform.