Concord Consortium: How Loud, How High?
This simulation-based resource from the Concord Consortium is the key activity featured in this AAPT Digi Kit. Students will hum and sing various pitches and volume levels, using microphones on computers or tablets. The digital tool transforms their voice recordings into graphs of Sound Intensity vs. Time or Frequency vs. Time. By viewing graphs of their own voices in real time, kids can deeply explore factors that affect amplitude, wavelength, pitch, and frequency of sound. A host of tools are available to registered teacher-users, such as class rosters, Snapshot uploading, and student performance tracking. Registration is free and easy.
website
PhET Simulation: Sound
This interactive Java simulation has a suite of tools to explore sound waves. Frequency and amplitude can be controlled, and students can enable audio tones to explore how pitch is related to frequency. Use the "Two-Source Interference" mode to demonstrate constructive and destructive interference by moving the position of audio speakers and a listener.
website  -  details