Does Sound travel through air slower than water?

Answer 1

Let's break this question down into several different parts.

1) Does sound travel slower in denser materials? Short answer is yes. High inertial properties slow down longitudinal waves (which sound is), but unless you are dealing with similar substances this is not necessarily the greatest factor. For example, sound moving from air (mostly nitrogen molecules) to a very dense gas like sulfur hexafluoride is going to slow down quite a bit (sulfur hexafluoride is commonly used as a sound insulating medium).

2) Does sound travel slower in media with greater elasticity? No, it travels faster. For example, hard metals (aluminum, for example), have very high elasticity and sound travels extremely quickly (~15X air, for aluminum). The reason is that the structure of the atoms more readily transmit force, and with less loss.

Both of the above can be seen from the basic property of sound speed, which, in simple terms is

speed = k Sqrt(E/d) where k is some constant, E is elasticity (Bulk modulus) and d is density (usually represented by the greek letter rho).

3) Does sound travel slower in media at higher temperatures? No, more energy improves the ability of the molecules to transmit for, and increases speed. For example, the speed of sound in air at different temperatures is

speed = (331.3 + 0.606T)m/s where T is temperature in Celsius

4) Does sound travel slower at low altitudes? Air is almost ideal, so the speed changes with respect to temperature and not density. The temperature generally declines at higher altitude (meaning slower sound), but some higher layers are warmer because they insulate lower layers from the sun.

Also the "amount" of sound decreases with lower density. Lower density means less molecules running into your eardrum. Eventually, in space, there are no molecules and no sound.

Answer 2

The speed of sound in water and air are as follows.

v (air) = 340 m/s.

v (water) = 1482 m/s

Short and simple:

Sound is a compression (or pressure) wave.

There are two things that affect the speed of sound, the density of a material and its compressibility. Specifically, the speed of sound is proportional to the square root of the ratio.

v=sqrt(B/rho)

v=speed of sound.

B= bulk modulus. (There are different names for this material property such as coefficient of stiffness).

rho= mass density.

A greater density of a material tends to slow the velocity of sound but a greater stiffness tends to increase the velocity of sound.

The bulk modulus of water is 15,000 times greater than air while the density of water is not even one thousand times greater.

Bulk modulus wins out and the velocity of sound in water is more than four times the velocity in air.

This relationship causes the speed of sound to be greater in most materials, but there are exceptions.

More Details:

The reader should be warned that there is much more to sound in materials than one see in the simple compression waves of air. Further, materials like steel come in various compositions and the micro structure depends on the processes that make it, so there is no such thing as a single number fore the speed of sound in steel.

Here are a few typical numbers for bulk modulus (stiffness) and density.

Air(adiabatic)

B= 1.42×10^5 Pa rho= 1.22 kg/m^3

Water

B=2.2×10^9 Pa rho= 1,000 kg/m^3

Steel

B= 160 x10^9 Pa rho=7,860 kg/m^3

v_air = 340 m/s.

v_water = 1482 m/s

v_steel= 4500 m/s

Caveat: As stated above, these numbers should be taken as approximate since various complications such as temperature and composition have not been explained.

Answer 3

Any variation in speed with altitude is swamped by variations in what is in the air. Air is such a horrible mixture that engineers use a theoretical International Standard Atmosphere for their calculations, knowing that there is no such thing in real life. A shower of rain for instance changes the speed of sound.

Answer 4

Sound travels slower in air at high altitudes than at low altitudes.

Answer 5

It all depends because sound can only travel through a solid, liquid or gas, if there is less air then the sound will travel more slowly.