What Is the Sound? is a 2004 Bear in the Big Blue House activity book featuring reusable pages and punch-out stencils. In this book, readers learn about sounds -- specifically sounds that letters of the alphabet make. For example, in one scene, the characters are seen having dinner by a campfire. As they use various utensils and enjoy their food, Bear comments, "Plate, pot and pie begin with the same sound. How many plates can you find in the picture?"
In this book, Bear and his friends go on a camping trip. They splash in the water, fly kites and later set up tents to sleep in. This book is illustrated in an original style, as opposed to some Bear books which combine photos of the characters with original illustrations. There are a total of fifteen story pages, including the activity pages.