subject verb agreement

[eden baylee]

Hi,

I need assistance with the following sentence. Which is correct?

The rumble of the explosions was deafening.

or

The rumble of the explosions were deafening.

I know rumble is the subject, however, it's a bit confusing to me since it's the explosions that are actually creating it.

Many thanks.

[Barb_D]

Rumble ... was.