Chapter 2

CHAPTER 2 After the bats had flown off for their nightly hunt, the kids went back inside. Lydia ran upstairs to get Abbi's phone and mic, while Daniel and Abbi decided on snacks for the rest of the evening. "Chips?" Daniel asked, looking into the pantry. Barkley sat dutifully at his feet, hoping for a treat. "We had chips with lunch," Abbi said. "Popcorn?" Daniel shook his head. "It gets stuck in Lydia's teeth. We'd have to listen to her complain about it all night."

Abbi laughed. "Good point." Wallis Wallace, Abbi's mom, strolled into the kitchen. She was balancing her laptop on one arm and holding a mug in the other hand. A familiar sight when she was on a book deadline! "What would bats snack on?" Wallis asked as she headed for the stove. "Fruit! That's a great idea, Mom!" Abbi said, then paused. "Or insects." "Mmm, delicious," Abbi's mom said, smiling.

Lydia bounded back into the kitchen and placed Abbi's phone in front of her on the table. "What's delicious?" "Bugs," Daniel said. "Hey, bugs can be delicious, you know!" Lydia replied. Wallis moved the teakettle from the counter onto a burner. "That's true! But sadly, we don't have any fried silkworms or caterpillars on hand." Daniel grabbed two pears and a red apple from the fruit bowl on the counter and stood between his sister and Abbi. "Fruit it is, then." Barkley settled under the table. Maybe someone would slip him a bite of apple peel or a chunk of juicy pear! Abbi opened the recording app on her phone and clicked on the most recent file. Two graphs popped up on the screen.

"What does all that mean?" Lydia asked, pointing at the images. Daniel leaned over for a better view. "This wave on the top looks like what we learned about in science," he said. "See how it goes up and down?" "Exactly!" Abbi said. "These are the sound waves the bats make. And then this other one shows the frequency—or at what pitch the sounds are. Bat calls are really high-pitched."

"What's that second graph called again, Abs?" Wallis said from the stove, waiting for her water to boil. "A spectrogram!" "Such a good word," Wallis said, mostly to herself. "I need to write that one down so I don't

forget it again." She wandered into the living room. Abbi used the touchscreen to scroll through different images. She frowned. "Something doesn't look right, though." "What's wrong?" Lydia asked. "The waves." Abbi pointed to the top graph. "They're too long to be from a bat, and the amplitude seems too high." Lydia tilted her head. "Amplitude sounds familiar. Did we learn about that, too?" Abbi nodded. "It means the height of the wave. Oh, I hope nothing got messed up! Maybe I didn't set the right threshold?" Daniel looked at his sister and raised a brow. Lydia shrugged. She didn't understand any of this, either. "Let's listen to it," Daniel said. Abbi nodded. Her finger hovered over the play button. Just then, an ear-piercing whistle filled the kitchen! All three of them jumped.