And why is it about 343 ms/s in air?
In: Engineering
sound waves can only propagate through a medium, and the medium through which they travel will affect the speed of the waves. Through gases and liquids, sound waves are longitudinal compression waves; when you hear a sound, you are actually detecting the changes in pressure caused by whatever created the sound. Think of a big speaker; the cone of the speaker is pushing and pulling the column of air in front of it, compressing and relaxing the column at whatever frequency is driving the speaker. Your ear drum feels the changing pressure at the same frequency and you hear the sound. If the molecules this pressure is pushing/pulling are heavier or lighter (really, if the gas is more or less dense), they will be pushed less/more, and the speed of the wave will change.
There’s also another property of substances called a bulk modulus; this is basically how easy it is to compress; the easier it is to compress the easier sound will travel through it. Speed of sound is the square root of this bulk modulus divided by the density. Working that all out for air at 20 degrees C at sea level gives ~343m/s
Sound propagates (spreads) through a medium. Something that can ‘carry’ it essentially.
Sound is vibrations in the air, and the density (how ‘solid’ it is) of the medium primarily dictates how quickly you can essentially ‘vibrate’ it with other vibrations. The speed of sound is dictated simply by how quickly those vibrations can in turn vibrate other things through a medium, it’s just that our most common medium sound travels through is air, so we say that the speed of sound is roughly 340-350m/s
At sea level, it’s about 340ms.
In solid objects like metal, you can get up to multiple KM/S, like being able to hear a train coming when you put your ear to the track but it’s miles away.
In something like space it’s 0 because there’s not much of anything to bump into anything else to propagate the sound.
Sound is a mechanical wave. It is literally things bumping into one another. Usually, those things are molecules of air, but it could also be molecules of water (why you can still hear under water), or molecules of string (how a tin can phone works). There is a “speed” of sound as it takes times for each one of those molecules to move and bump into the next one. The speed of sound varies and is directly related to the density of the medium it’s traveling through — in other words, how tightly packed the molecules are. The speed of sound in air actually varies depending on the density of the air which can be changed due to elevation, temperature, and barometric pressure.
The speed of sound is fundamentally determined by the properties of the medium through which it travels, and it exists because sound itself is a mechanical wave that requires a medium (like air, water, or solids) to propagate. When an object vibrates, it causes the particles in the surrounding medium to oscillate and bump into adjacent particles, transferring energy from one particle to the next. This chain reaction of vibrating particles creates what we perceive as sound.
The speed at which this energy transfer occurs varies depending on the medium’s properties, particularly its elasticity and density. Elasticity refers to how well the medium can return to its original shape after being disturbed, which facilitates the transfer of sound waves. Density affects how closely packed the particles are, with denser media typically slowing down the propagation of sound because the particles are closer together and more difficult to move.
In air at sea level and at a temperature of 20°C (68°F), the speed of sound is approximately 343 meters per second (1,125 feet per second). In water, sound travels faster (about 1,484 meters per second) because water is more incompressible and denser than air, allowing sound waves to be transmitted more efficiently. In solids, the speed of sound is even faster due to their tightly packed molecules and high elasticity.
Thus, the speed of sound exists as a measurable velocity due to the nature of sound as a mechanical wave and the characteristics of the medium through which it moves.
That’s how fast wiggly air causes it’s neighbor to wiggle, because that’s the speed of sound through air.
Sound travels through solid objects waaaay faster since the atoms are closer together. When an atom vibrates, it shakes all the stuff around it. That’s sound propogating through the stuff. Sound travels through air in the exact same way, but there’s more space between the atoms so there’s more lag between an atom shaking and it shaking it’s neighbors.
Because that’s what sound is: Vibrations.
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