I've heard that secondary stress is more weaker than primary stress but aside from that is there any noticeable difference the two kinds of stresses?
Phonetically, "stress" isn't a clearly-defined thing. It tends to refer to a combination of pitch and amplitude and some other factors that's phonologically significant in certain languages. So secondary stress might have a little bit less of all these factors, or it might not: it depends on the language, and what exactly the phonologists are slapping the "stress" label onto this time.
Phonologically, "stress" is a property that's useful for describing certain languages. Sometimes it's a binary property—every syllable is either stressed or unstressed—or maybe it happens at only one position in the word, with every word (or most words) having a single "ictus" in it.
And sometimes it's more useful to not treat it as a binary property, and treat it as something else instead: maybe every syllable is either "primary stressed", "secondary stressed", or "unstressed", and that's important for the language's phonology. Maybe every second syllable before or after the ictus is phonologically important (certain sound changes only happen in those syllables), so it's convenient to have a name for them. That's another reason to bring out "secondary stress" as a label.
In the end, this isn't really a term that has a consistent meaning across languages, either phonetically or phonologically. Anyone using it in a grammar should explain what exactly they mean by it in their particular case.
I thought it was about the differences in "relatively" more or less a degree of stress based on the strength of the voicing of a given person.
1Your answer could be improved with additional supporting information. Please edit to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers in the help center.– Community BotJan 10 at 11:09