This ‘How To’ is about using SpectrumViewPlus on an Apple iPad to investigate noise. It’s prompted by a thread in ‘Technical’ about TCN (Tyre Cavity Noise). Rather than give a full-on instructional it would be better, I thought, to just introduce app and see where it goes, so .. Here are a couple of examples from that thread showing the TCN in my W205 C Class: The first is a Fast Fourier Transform (FFT) ‘snapshot’ of the TCN - shocking isn’t it? The second is a Spectrogram showing the full half-minute or so test from which the first was taken. This is my ‘test’ setup I use: The iPad is secured to a couple of foam blocks on the front seat with the microphone forward and unobstructed - the TCN comes into the cabin through the footwell. If you’re interested I suggest you download the free version of SpectrumView, have a play, then get back and we can have a chat. You will need the full SpectrumViewPlus to do proper testing - I think I paid £8. Finally here are the 2 record settings I use: None of the other settings really matter.