Dimensions of a spectral representation I'm currently trying to perform analysis of a spectrogram, with the use of PCA.
I'm confused about what the dimensions of the result should therefore be. Currently, the dimensions are: 451x128. But I thought that it was a standard image, and therefore it should have 2 dimensions.
It does have two dimensions. An image of size $N \times M$ has two dimensions. Three dimensions would be $N \times M \times L$, and so on. For each pixel with coordinates $x$ and $y$, in two dimensions, you have a spectrum magnitude value.

However, if you start treating rows or columns of your spectrogram as vectors, then you're interpreting them as 451 points in 128-dimensional space or 128 points in 451-dimensional space. This is different.