Final answer:
The sentence suggests that the sound of rain hitting the window was a pleasant lullaby that helped the person fall asleep.
Step-by-step explanation:
The sentence suggests that the sound of rain hitting the window was perceived as a pleasant and soothing lullaby that helped the person fall asleep.
The use of the word 'lullaby' indicates that the person found the sound calming and peaceful, similar to the way a lullaby can help babies and young children sleep.
This implies that the sound of rain hitting the window was not distracting or loud, but rather a gentle and pleasant background noise.