SOUND & TECHNOLOGY

HOW SOUND TRAVELS

Sound waves travel in Gases, Liquids and Solids.  They travel fastest in solids (due to the more tightly packed molecules), and slowest in gases such as Air.

Sound speed in air is also affected by temperature, traveling faster when it’s warmer.  Pressure and winds can also have an affect on sound travel in air.   Sound in water can travel much farther than sound in air, which is how whales communicate over long distances.  Human ears evolved to hear in air, not water, so people hear sounds underwater mostly through bone conductivity (the bones of the skull pick up the vibrations).

Sounds travel, bounce or objects, and are absorbed.  Anything dense and hard enough will reflect sound, but anything soft enough to absorb the sound wave vibrations will limit or even stop sound. 

As sounds travel, they change. Sounds do not reach both of your ears at the same time, and also are drastically changed when they reach each ear.  This is an important part of being able to tell the direction a sound is coming from.  How sounds change when they bounce can be used to tell direction, distance, and even speed. 

You can tell direction from high frequencies, but not low frequencies.  That is why a sound system can have a subwoofer (low frequency speaker) anyplace without disrupting the stereo image of the sounds being heard.

Some animals rely heavily on listening to how sound bounces to learn about their environment, especially when unable to rely on sight.

As sound waves travel through air they hit objects and either bounce off or are absorbed (depending on the properties of the ssurface). Hard surfaces reflect sound and soft surfaces absorb sound.  Parallel surfaces allow waves to bounce back and forth (like light does in mirrors that are facing each other).  Non-parallel surfaces also create reflections, but they will be scattered rather than bouncing back as a recognizable echo.

When someone is speaking to you the sounds from their throat and mouth are going out into the room.  In the course of their travels and bouncing around the room, some of the waves are going directly to your ears and some are getting there after bouncing off of a hard wall or table.  Some of the sound waves are being absorbed into the soft surfaces within the room, such as the carpet and your clothing.

If you pay attention to the shape, dimension, surface materials, and contents of any room while clapping, you will be able to better understand how all of these factors affect sound.

There are new devices that allow you to concentrate sound into a beam (like a flashlight), but when these beams of sound hit things, they will still bounce.