The poor woman didn't know that this strange sound was the sound of her husband and 4 other people vaporizing in fractions of a second:
Wendy was aboard the support ship for the Titan submarine expedition, and her husband Stockton was piloting it, with 4 other people on board.
During her monitoring of the expedition, she heard a sudden booming sound and asked those present: What is this sound?
She didn't know that the sound she heard was the result of the catastrophic collapse of the submarine under water pressure, which claimed the lives of her husband and the other four in moments.
What happened is called implosion, an internal collapse due to the immense water pressure that crushed the submarine.
Most tragically, she continued monitoring the expedition, believing her husband was still alive.
For after hearing the booming sound, a message arrived from the submarine indicating that it had jettisoned two weights, leading the crew to believe it was still operational. But the message had been sent before the submarine's collapse and arrived late.
From the looks on the faces of the two men behind her, it seemed they knew what had happened but chose to remain silent.