Engine Fault Diagnosis by Audio Analysis
I am currently completing an MCS in Computer Science. My masters dissertation is on Engine Fault Detection using audio analysis. The goal of the project is to find out, to what degree can Internal Combustion Engine health can be determined by using a smartphone microphone.
The idea originated from a tappet sound on my infamous 2002 Audi TT. At the time, I didn’t have enough knowledge or experience in the field to identify the sound. However, an expert mechanic could instantly identify the tappet sound and recommend a fix.
At the most basic level, this project could prove useful to create a tool that identifies basic faults for a non-mechanic. If the project is more successful, it may very well be able to identify faults from sound that even an expert mechanic is unable to notice.
To acquaint myself with audio analysis techniques, my first task is to determine the RPM of the engine from its sound. I opted to perform a Fast Fourier Transform on the audio and find the fundamental frequency of the cylinders firing to determine the RPM.
Misfires occur when the fuel and air mixture in a cylinder doesn't combust. This can be caused by spark plug, injector or coilpack faults. To find a misfire, I used a Fast Fourier Transform and used harmonics of the fundamental frequency of the cylinders and the presence of intermediate frequencies between the harmonic frequencies to determine a misfire.
Cylinder compression is a great metric for determining engine health. If a cylinders compression varies greatly from others, it is often an indicator of poor engine condition. I used the sound of the starter motor cranking the engine to determine the relative compression of each cylinder.
In part 1 of this review I discussed Shazam’s method of creating a unique fingerprint for a song. In this part I am going to discuss how Shazam uses these fingerprints to efficiently identify a song from a partial recording.…
Shazam is a mobile app that allows you to identify any song in their database by recording the song using your phones microphone.…