Investigating the Dependence of SoS on Pressure & Temperature

In summary, the commonly held view is that the speed of sound in a gas is dependent on temperature rather than pressure. However, this is only true for an ideal gas. In the first case of a cylinder made of a bad conductor of heat, the increased temperature results in a higher SoS due to higher molecular velocities. In the second case, where the cylinder is made of a good conductor, the heat of compression is lost to the surroundings and the SoS will be the same as the outside temp. However, due to the increased density of the gas, any disturbance (sound) will propagate quicker than at atmospheric pressure. This is not always the case and should not be used as a proof of independence of pressure on
  • #1
RKT
18
0
SoS again ...

Hiya ,

The commonly held view is that speed of sound (SoS) in a gas depends on temperature and not pressure. I want to know if this is always true. Consider the following two cases and let me know what you think.

In the first case, we have cylinder made of a bad conductor of heat such some strong plastic or something. The gas is compressed in the cylinder. Here the temperature will rise and the heat more or less is confined to the cylinder. SoS will be higher than at normal temp. as the increased temperature results in higher molecular velocities inside the cylinder. Fair enough.

In the second case, the cylinder is made of a good conductor such as a metal. Here the heat of compression will lost to the surroundings within a few minutes. The temp. inside the cylinder will be the same as the outside temp. by then. Theory says that since the temp. is the same, the SoS inside will the same as outside.

My question : For the second case, given that the molecules are packed much more closely than at atmospheric pressure, won't any disturbance (sound) propagate quicker than at atm. pressure ? When I researched the dependence of SoS of a gas on temp. and pressure on the net, I observed that writers always cite the behavior of sound in the Earth's atmosphere as proof of independence of pressure on SoS. To my mind, this is not a good example because this looks like just one particular case where pressure indeed has no bearing. In the atmosphere a change in pressure usually means a change in temp. as well and vice versa so one need not consider the two seperately.

Regards
RT
 
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  • #2
RKT said:
Hiya ,

The commonly held view is that speed of sound (SoS) in a gas depends on temperature and not pressure. I want to know if this is always true. Consider the following two cases and let me know what you think.
Only true for an ideal gas - a real gas it depends on temperature (mostly) and density (slightly)
 
  • #3


Dear RT,

Thank you for your inquiry about the dependence of speed of sound (SoS) on pressure and temperature. I can assure you that this is a topic of ongoing research and there is still much to be learned about the relationship between these factors.

While it is commonly understood that temperature has a greater impact on SoS than pressure, it is not always the case. As you have pointed out, in certain situations, pressure can also affect the speed of sound. In the example of a cylinder made of a good conductor, the heat of compression may dissipate quickly, leading to a decrease in temperature and ultimately a decrease in SoS. However, it is important to note that this is not a universal rule and the behavior of SoS in various scenarios can be complex and unpredictable.

Furthermore, the behavior of sound in Earth's atmosphere is not the only example of the independence of pressure on SoS. In fact, there are many other examples where pressure does not have a significant impact on SoS, such as in solids and liquids.

In conclusion, while temperature is generally considered to have a greater influence on SoS, it is important to consider both temperature and pressure when investigating this phenomenon. Further research and experimentation are needed to fully understand the relationship between these factors and their impact on SoS.

Best regards,
 

1. What is the purpose of investigating the dependence of speed of sound (SoS) on pressure and temperature?

The purpose of this investigation is to better understand the relationship between SoS, pressure, and temperature. This can help us to make more accurate predictions and measurements in various fields such as meteorology, seismology, and fluid dynamics.

2. How is the speed of sound affected by changes in pressure and temperature?

According to the ideal gas law, as pressure increases, the density of a gas also increases. This causes the molecules of the gas to be closer together, resulting in faster vibrations and a higher speed of sound. Similarly, as temperature increases, the molecules in a gas have more energy and vibrate faster, also increasing the speed of sound.

3. What methods are used to investigate the dependence of SoS on pressure and temperature?

There are several methods that can be used, including using a resonance tube, measuring the time of flight of sound waves, and using computer simulations. Each method has its own advantages and limitations, and the choice of method will depend on the specific goals and resources of the investigation.

4. What are some practical applications of understanding the dependence of SoS on pressure and temperature?

Understanding the relationship between SoS, pressure, and temperature has various practical applications. For example, it can help in designing and optimizing engines, predicting the weather, and detecting and monitoring seismic activity. It can also be useful in fields such as medical imaging and underwater acoustics.

5. Are there any limitations to investigating the dependence of SoS on pressure and temperature?

While investigating the dependence of SoS on pressure and temperature can provide valuable insights, there are some limitations to consider. For example, the ideal gas law may not accurately describe the behavior of all gases, and there may be other factors at play, such as humidity, that can also affect the speed of sound. Additionally, the accuracy and precision of the measurements can also impact the results of the investigation.

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