A supernova remnant is the structure resulting from the explosion of a giant star. The supernova remnant is surrounded by an expanding shock wave that is formed from material ejected by the explosion and interstellar material swept away during the process.
When this material collides with the circumstellar or interstellar gas, it forms a shock wave that can heat the gas at high temperatures up to 10 million K, forming a plasma.
The first question is: exactly what is the material ejected by the supernova?
The other issue is: if we consider for a moment the idea that a "human" might be witnessing the exact moment of the explosion of a supernova, the "superhuman" would hear the explosion? That is, does the explosion produce some kind of sound?