Sound is vibration, as perceived by the sense of hearing. Vibrations usually travel to our ears through the air; the ear converts them into nerve impulses sent to our brains, where the impulses become sound. In more technical language, sound "is an alternation in pressure, particle displacement, or particle velocity propagated in an elastic material" (Olson 1957) or series of mechanical compressions and rarefactions or longitudinal waves that successively propagate through media that are at least a little compressible (solid, liquid or gas but not vacuum). In sound waves parts of matter (molecules or groups of molecules) move in a direction of the spreading of the disturbance (as opposite to transversal waves). The cause of sound waves is called the source of waves, e.g. a violin string vibrating upon being bowed or plucked. A sound wave is usually represented graphically by a wavy, horizontal line; the upper part of the wave (the crest) indicates a compression and the lower part (the trough) indicates a rarefaction.
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- Musical Acoustics Learn about acoustics of different instruments, the sound spectrum, standing wave patterns supported by different air columns on this page by The University of New South Wales, Australia .
- Sounds and Noise Try these experiments which show the physics of sound waves by using objects around the house to demonstrate how they travel.
- The vOICe Sonification Applet - Draw your own Sound Lets explore synthetic sound and vision with a voice mapping Java applet. Also, sonify the pre made images, or make new ones.
- Standing Sound Waves Uses diagrams to show pressure nodes and internodes of harmonics in a pipe.
- Sounds Amazing Learn all about sounds and waves through a graphical-learning based interface in four lessons.
- Looking at Sound Detailed look at how sound can be analyzed with a microphone and oscilloscope with clear examples of expected results.
- AS Sounds Amazing Offers experiments and demonstrations designed to help you understand sound, waves and acoustics.
- Sound Waves and Music Offers an animation of how high and low pressure waves make the eardrum vibrate along with information on how the journey of sound waves affects the brain.
- The Doppler Effect and Sonic Booms Explore in detail the wave front diagrams of stationary and moving sources at both subsonic and supersonic velocities.