- #1
PainterGuy
- 940
- 69
Hi,
Once someone wrote the following to me in response to my query. My query was somewhat unrelated to it and I don't even have the copy of query anymore.
The pressure felt by the piston at any time is the average component of momentum of a gas molecule that is normal to the piston times the number of molecules striking it per second. The increase in the pressure against the piston when you move it will be the ambient pressure times the mach-number of its speed.
With normal day-to-day sounds -- even the loud ones like a rock concert, the mach-number of object making the sound is a tiny fraction. Say a speaker is making a 60 hz sound and travels 2 cm from crest to trough. Then its max speed is 2pi 60 hz times 1 cm = 377 cm/sec = 3.77 m/sec for a mach number of about 0.01. Such a speaker, assuming it was large would make a very loud sound.
"ambient pressure" - I think it refers to the external pressure applied by an outside agency and this pressure results in compression(or, expansion?) of the gas. So is the total pressure felt by the piston = (piston times the number of molecules striking it per second) + (ambient pressure times the mach-number of its speed)?
"2pi 60 hz times 1 cm" - Where does this formula come from? How is it derived?
Thank you for your help!
Once someone wrote the following to me in response to my query. My query was somewhat unrelated to it and I don't even have the copy of query anymore.
The pressure felt by the piston at any time is the average component of momentum of a gas molecule that is normal to the piston times the number of molecules striking it per second. The increase in the pressure against the piston when you move it will be the ambient pressure times the mach-number of its speed.
With normal day-to-day sounds -- even the loud ones like a rock concert, the mach-number of object making the sound is a tiny fraction. Say a speaker is making a 60 hz sound and travels 2 cm from crest to trough. Then its max speed is 2pi 60 hz times 1 cm = 377 cm/sec = 3.77 m/sec for a mach number of about 0.01. Such a speaker, assuming it was large would make a very loud sound.
"ambient pressure" - I think it refers to the external pressure applied by an outside agency and this pressure results in compression(or, expansion?) of the gas. So is the total pressure felt by the piston = (piston times the number of molecules striking it per second) + (ambient pressure times the mach-number of its speed)?
"2pi 60 hz times 1 cm" - Where does this formula come from? How is it derived?
Thank you for your help!