Other
Amplifon: Interactive Ear: A Guide to Human Hearing
The Interactive Ear is a whole ear model which allows the user to explore all the inner-workings of the human ear.
Physics Classroom
The Physics Classroom: Sound Properties and Their Perception
The concept of pitch and frequency is covered in this tutorial. Learn what frequency and pitch are, the difference between infra sound and ultrasonic frequencies, and how pitch is related to the frequency of a sound.
Physics Hypertextbook
The Physics Hypertextbook: The Nature of Sound
Study the details of sound from characteristics to speed, ultrasound, infrasound, and other aspects of sound waves.