The document is a student's notes on sound waves from a class. It recaps key concepts about sound waves, including that time period varies inversely with frequency, and speed of sound decreases from solids to gases. It also contains review questions on how the eardrum responds to sound waves, the relationship between wave velocity, frequency, and wavelength, and calculating time period, frequency, and time taken for a sound wave to travel a distance. References at the end include the textbook, websites, and YouTube videos used in the lesson.