Checking .wav files for similarity

I'm trying to compare .wav files for similarity. I used the google musicg library for that but I get bad solution for similar sounds. I compare two car motor sound from the same car and the recordings sounds very similar for a human but I get fingerprintSimilarity scores like 0.012468828. The recordings are made with a microphone.

What is the problem that I get that bad scores?

I use:

Wave wave = new Wave("wav1.wav");
Wave wave1 = new Wave("wav4.wav");
FingerprintSimilarity fingerprintSimilarity = wave.getFingerprintSimilarity(wave1);
float score = fingerprintSimilarity.getScore();
float similarity = fingerprintSimilarity.getSimilarity();
System.out.println("Similar sound :"+ "Score : " + score + "\n  Similarity : "+ similarity);