I am studying Speech Recognition from Rabiner's book. In this book the author has asked a question
Explain the distinct speech production process for producing voiced, unvoiced and plosive sounds
The author says :
When vocal cord is tensed + air flow then voiced sound
When vocal cord is relaxed + air flow then unvoiced sound
But nothing is said about plosive sound, yes he does mentions about transient sound.
So is transient sound same as plosive sound?
I think the way you are categorizing things may be confusing you. Voiced and unvoiced are two types of sounds in a particular category. Plosive sounds could be either voiced or unvoiced; it is not a third type of sound in the same category.
As for your original question, I would not consider plosive and transient sounds to be equivalent. Plosive sounds are when you temporarily block air from exiting and then release it all at once--think about making a 'b' or 'p' sound. Transient sounds are like clicks, pops, or bangs. A short, impulsive sound. Plosives can be similar, but they can also be more extended in duration.
One more thing about vocal cords. I think that terminology gives the wrong image. You don't have cords or strings in your throat that are tensed or relaxed. You have two folds that can come together or remain open. An unvoiced sound is when the folds are relaxed and apart. A voiced sound is when the folds are beating against each other at a regular interval, many times per second.