The birdsong stops

Original fiction extract.

The recording had been playing for ten minutes while we tried to identify the birds. I had just persuaded myself that one call belonged to a thrush when the sound stopped abruptly. My brother looked up from his sheet. There was no final announcement or fading music, only the small click of the speaker. On the table, the phone displayed an empty battery. We could still hear the real sparrows outside the window. My brother wrote their name on his sheet, though I pointed out that they were not part of the test.

Use your own words to explain what the word “abruptly” means in this extract.