I was wondering if the spectrogram can be used as a MATLAB tool to check whether or not aliasing will occur when the signal is downsampled from let's say, 44.1kHz to 8kHz? And if yes, how do I go about it?
If the spectrogram displayed is sensitive enough to show spectral energy from half the old sample rate to half the new sample rate (e.g. anything at or between 4 kHz to 22.05 kHz), that energy will be aliased unless low-pass filtered out before or during downsampling (to 8KHz). If there is nothing there, then there is nothing that will be aliased by properly interpolated (Sinc kernel, et.al) downsampling without any further low-pass filtering (such as a wider windowed Sinc FIR kernel, etc.)