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The SOUND PAGE displays some text in the top edit control that explains what sound is, and how it is created. You can click on the blue box below (or drag your mouse across it) to create some interesting waves, and watch as they bounce off of the edges, creating "reflections" (also called echoes). By changing the value in the spin control, you can change the apparent density of the medium through which the sound travels, thereby increasing or decreasing the speed of the waves propagating through the medium. You can click on one of the yellow balls to create a single note, and watch as the waves generated by the note travel through the medium. Clicking the Internet Links button pops up some interesting related links on the Internet. Clicking the "Take Quiz" button pops up a short quiz, which you can score yourself, to see how much information you learned in this lesson.

The HEARING PAGE provides information about the anatomy (structure) and physiology (function) of the human auditory system, and how sound waves entering the ear are converted into electrical impulses (called "action potentials") that travel from the ear up the auditory nerve to the brain, where they are interpreted as sounds. The "Show Sound Entering The Ear" button pops up an animated gif image that shows how the tiny middle ear ossicles (bones) move back and forth (with a mechanical advantage) when the tympanic membrane (ear drum) vibrates. This creates a pressure wave in the inner ear fluids, which causes some tiny neurons (hair cells) that have even tinier hairs sticking up out of their top surfaces, to wiggle back and forth. This movement opens or closes sub-microscopic channels on the hair cell surfaces that in turn let charged ions (sodium and potassium ions) move into or out of the hair cells, in turn changing the electrical potential (voltage) across their membranes, in turn causing action potentials to be generated in the auditory nerve fibers.

Clicking on the "Show Hearing YouTube Videos" button pops up the built-in YouTube Player with the selected video. (Your computer must be connected to the Internet for this option to work.) One of the YouTube videos shows a really cool depiction of how the different frequencies of sound are spread out across the basilar membrane, in turn activating a specific set of hair cells. Be sure to have your speakers turned on and your computer connected to the Internet, so that you can hear and watch what's happening.

The MUSIC PAGE teaches you about the different musical instruments used in a symphony orchestra. Clicking on the "Musical Instruments" button allows you to examine each type of instrument, which are grouped into Strings, Woodwinds, Brass, Percussion, and Keyboards.

For example, selecting "Brass" lets you see each type of brass instrument. For each instrument, there are two choices: If you don't have the "Use QuickTime Plugin" radiobox checked, the program will show an animated gif graphic of that instrument rotating 360 degrees.

If you click the "Play Sound" button on the top of each image, you can hear the sound of that instrument. If the "Use QuickTime Plugin" radio button is checked, the program shows a cool image of that instrument, which you can rotate yourself, by dragging your mouse across the image, with the left button held down.

The CREATE MUSIC PAGE teaches you about the different symbols that are commonly used to write music so that other people can read and play it. This is called "musical notation". Here are presented some of the concepts and symbols used to write music: The "Create Your Own Music" button pops up the Anvil Midi Sequencer, with which you can compose and play your own music. The Anvil Help File explains in detail how to create and save your own musical score, using the mouse to drag specific notes, key signatures, rests, ties, etc. to each staff.


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