You can modify the sound directly. One way is to mix in some random noise, like a static sound, by adding small, random variations to the audio data (without multiple audio lines). Another option is to change the way the sound waves behave, such as making them louder or softer suddenly, which creates a crackling or distorted effect. You can also lower the quality of the sound by reducing its precision, making it sound rougher, like a weak radio signal. Here is a code that chatGPT gave me for an example of modifying a single SourceDataLine with noise:
byte[] buffer = new byte[1024];
while (line.isOpen()) {
for (int i = 0; i < buffer.length; i++) {
buffer[i] += (byte)(Math.random() * 10 - 5); // Adding noise
}
line.write(buffer, 0, buffer.length); // Write modified data\