How is air nonlinear?

Question

what is meant by non linearity of air?
acoustics

Answer 1

Nonlinear is a term used to relate one property to another. If the two properties are related so that a change in one property causes the other to change proportionally, they are linear. One way of looking at this is if you were to graph one versus the other, you would get a straight line with the slope being the ratio of the rate of change of one compared to the other.

For example, solids, liquids and gases tend to expand proportionally to temperature.

Properties are nonlinear if they are not proportional to each other. For example, if one varies as the square root of the other, or the second or third power of the other, they are nonlinear.
Air has many properties that are nonlinear. For example, the speed of sound in air is nonlinear when compared to the air temperature.

Answer 2

What is usually meant by a linear equation is of the form y=ax + b
If something is nonlinear it means that it has a property that can not be modeled by this kind of equation.
While I am not sure what property of air you are refering to I will use an example.
The force or air resistance or drag for a slow object can be modeled a F=av
While for a faster moving object you need to add more terms to make an accurate prediction
F=av + bv^2

Of course the values of a and b depend on the shape and size of the object and the density and exact compostion of the air.

Answer 3

Air is non-linear because it's mass does not change in a linear fashion when pressure is applied.

It especially becomes non-linear near the speed of sound. Before the sound barrier was "broken", it was believed that you could not travel faster than that. The idea is that you could try to go faster, but the amount of force to drive you faster, could not accelerate you beyond that point.

The same may be found true with the speed of light. But in this case, it is how matter becomes non-linear with relative speed. But that is an entirely different problem from your question. (interesting all the same)

Answer 4

Sound propagates as waves of compression and rarefaction through the medium, in this case air. Of course when you compress air, you heat it, and when you expand air, you cool it! As a result, Sir Issaac Newton overlooked this fact when he attempted calcuated the speed of sound based on the presure and density of the medium. He was off by a few percent, but that was still a pretty good approximation. Of course at very high sound intensities, the fact that air cannot be rarefacted beyond a vacuum, and the fact that at extreme temperatures the air would ionize each introduce some interesting limits on the maximum intensity as we would understand it of sound. Long before that, non linear effects would occur, introducing distortion in the same manner as in a non linear elecronic circuit.

Answer 5

There is an equation which is the air equation . Usuali]y a nonlinear equation is one whose response is not linear.
Linear means a direct prortionality which can be expressed as a straight line equation ;thus the term linear.

Answer 6

I think I know what you're talking about, and the term isn't nonlinear, it's inhomogeneous, or maybe nonuniform.

In other words....not uniform.

Air is a gas. It has pockets and regions of higher and lower density. Sound needs air to propagate, and these nonuniform regions can influence the integrity of the sound.

Answer 7

Air is not usually the same temperature and density throughout the path across which a given sound wave will travel.

Answer 8

I would guess that it referrs to the ability of sound waves to spread in all directions (3 dimentions) in air as long as nothing is blocking it. Sound doesn't just travel in the direction it is pointed to, as anyone with a noisy cubicle-mate will tell you.

Hmm, those answers are interesting... I'm learning something too!