The same power can be obtained by less air but at higher pressure, or more air at higher pressure.
How can you tune a PCP to be more quiet at a fixed power level?
How can you tune a PCP to be more quiet at a fixed power level?
N/A Tuning for silence
- Thread starter nobody1
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Mine seem to be quieter at a lower reg setting using the 95% method of your top velocity. If you are shooting for 880 fps, then adjust your reg till you reach 920 fps and start backing down the hammer spring till you are shooting 880. When I try to go with a higher reg setting and less hammer spring, it is louder because it is all working harder to open the valve at the higher reg pressure. Kind of a balancing act.
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For the same power level, a gun is typically more efficient with a higher reg pressure and less hammer (compared to less reg pressure and more dwell time). However, with such tune, the consistency tends to suffer since the gun is essentially operating at a partial valve lock.
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Higher pressures and larger ports require less dwell (time the valve is spent in open state) due to increased mass flow rate, resulting in the pressure gradient having a steeper slope down the length of the barrel, which nets a lower muzzle report.
If your hammer/action is louder, then, run a peek, or compressed leather striker (this requires a pocket for the compressed leather to sit in), but this noise only effects the shooter, not the potential target or bystanders.
Next option is moving to a much heavier ammo that moves slower. Shooting lighter pellets at 900 fps will be much louder than shooting heavier pellets at 600 fps at the same muzzle energy.
-Matt
If your hammer/action is louder, then, run a peek, or compressed leather striker (this requires a pocket for the compressed leather to sit in), but this noise only effects the shooter, not the potential target or bystanders.
Next option is moving to a much heavier ammo that moves slower. Shooting lighter pellets at 900 fps will be much louder than shooting heavier pellets at 600 fps at the same muzzle energy.
-Matt
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I think that the most efficient tune is also the most quiet.
The compressed air energy will go into the air propelling the pellet and the air exiting the barrel and making noise.
The more efficient tunes will have more air energy going into propelling the pellet and less air energy wasted.
The compressed air energy will go into the air propelling the pellet and the air exiting the barrel and making noise.
The more efficient tunes will have more air energy going into propelling the pellet and less air energy wasted.
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Goo insights!
Let's assume that everything is fixed, same power level, same caliber etc.
The only variables are the air pressure and hammer spring.
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Yes, heavier ammo has a lower speed, spends more time in the barrel and will more efficiently use the air, which means that there is less air exiting the barrel and making noise.
Now, let's assume that everything is fixed except for the air pressure and hammer spring.
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0 pressure and 0 spring is the quietest, likewise it won't be linear, depends on the muzzle velocity you're going for. There will be a bell curve, such as tuning at a ridiculously low pressure and accepting a very low muzzle velocity will be far quieter than anything else you can throw at it.
-Matt
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I think the OP already got the pressure/hammer spring answer. You need to set the regulator to give about 5% higher than the target velocity and then reduce the hammer spring until you get to the target. This is easier to say than to do, of course. The process usually requires several attempts for me since I don't really know exactly where to set the regulator to give 105% of the desired velocity. I also have to mess with the hammer spring after the regulator is set to see what the peak velocity is. If the peak is OK, I shoot some groups as I gradually turn the hammer spring down and sometimes I stop at a little higher velocity if the accuracy seems better.
Another good check on the tune is to shoot a few shots after the gun has set over night. If the first shot velocity is low and you don't want that, increase the hammer spring slightly and try again. If the first shot is higher than the subsequent shots then reduce the hammer spring a little. I've only done this once I can think of but the gun was extra noisy set that way. It was spewing out air unnecessarily was my impression. Shot count was also not good.
In picking your target velocity Matt has provided potentially useful input. Lower will be quieter.
Another good check on the tune is to shoot a few shots after the gun has set over night. If the first shot velocity is low and you don't want that, increase the hammer spring slightly and try again. If the first shot is higher than the subsequent shots then reduce the hammer spring a little. I've only done this once I can think of but the gun was extra noisy set that way. It was spewing out air unnecessarily was my impression. Shot count was also not good.
In picking your target velocity Matt has provided potentially useful input. Lower will be quieter.
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You're obviously looking for a very specific answer, but there just may not be one. It's all very relative. And the answer could even differ between calibers and speed ranges. "Quietness" itself is also quite relative. For example, the tune where you use higher reg pressure and lower hammer spring would likely produce more high frequency sound and less low frequency sound. Whereas your opposing scenario of less pressure and more dwell would likely produce less high frequency and more low frequency. So which one is quieter?? It depends...
So my advice to you is if you want such a specific answer relative to your gun, your ammo, your setup, and your sound suppression needs, then probably best for you to do your own testing. Just do yourself a favor and don't use one of those wildly inaccurate $20 dB meters from Amazon or Ebay. Use a proper microphone and audio software. This will give you very accurate readings for comparison, and will also allow you to break out specific frequency bands for analysis.
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The factor your missing is DWELL in being how long the valve stays open and flowing air.
The Profile of the valve opening and closing has a huge effect on the amplitude of the air pulse and it's contained energy effectively getting the projectile moving.
This rabbit hole of understanding all that's in play here goes quite deep.
Smashing a valve open with a heavy spring and/or hammer is generally very DWELL Long and not very efficient.
Using a Light hammer and a Heavy spring driving it gets the valve open quicker as the speed of hammer will be greater, tho with less hammer weight the valve can close faster too.
** IF, the balance of pressure, hammer and spring is tuned correctly the muzzle report becomes a sharp SNAP !!! and once an LDC is in place a dull pop and not a blaring blast.
Now this is a VERY simplified statement & in no way covers the deeper cause & effect of each part in play. Just food for thought
The Profile of the valve opening and closing has a huge effect on the amplitude of the air pulse and it's contained energy effectively getting the projectile moving.
This rabbit hole of understanding all that's in play here goes quite deep.
Smashing a valve open with a heavy spring and/or hammer is generally very DWELL Long and not very efficient.
Using a Light hammer and a Heavy spring driving it gets the valve open quicker as the speed of hammer will be greater, tho with less hammer weight the valve can close faster too.
** IF, the balance of pressure, hammer and spring is tuned correctly the muzzle report becomes a sharp SNAP !!! and once an LDC is in place a dull pop and not a blaring blast.
Now this is a VERY simplified statement & in no way covers the deeper cause & effect of each part in play. Just food for thought
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I am trying to use some rules of physics I learned long ago,
The air exits the air tank/tube, goes through the transfer port and gets behind the pellet.
The higher the pressure of the air the faster the air and the pellet move.
The air pressure and force will decrease as the pellet moves.
I think that a higher starting pressure will be more efficient than more air at lower pressure.
The air exits the air tank/tube, goes through the transfer port and gets behind the pellet.
The higher the pressure of the air the faster the air and the pellet move.
The air pressure and force will decrease as the pellet moves.
I think that a higher starting pressure will be more efficient than more air at lower pressure.
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This entirely depends on if you add another constraint such as 'muzzle velocity' or minimum energy.
If I didn't care about muzzle velocity and wanted to shoot a 1grain projectile made from paper, I would rather use 50 psi than 2500 psi.
-Matt
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Lol ... but wait there's more
Any release of air from a valve can follow differing profiles ... That of a slower rise in pressure having a mid full flow release and gradual closing ... OR, that of having the pressure rise very quickly within valves throat & behind said projectile giving lets say a MAJOR Ass Kicking to get projectile moving and then shut down just as quickly as opening. BOTH can give equal speed, but one is vastly more air use efficient yielding less muzzle report
Any release of air from a valve can follow differing profiles ... That of a slower rise in pressure having a mid full flow release and gradual closing ... OR, that of having the pressure rise very quickly within valves throat & behind said projectile giving lets say a MAJOR Ass Kicking to get projectile moving and then shut down just as quickly as opening. BOTH can give equal speed, but one is vastly more air use efficient yielding less muzzle report
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One more food for thought. You cannot objectively state "higher pressure is always quieter than lower pressure at the same muzzle energy" because, at some point that statement is false (low velocity, low projectile weights), then it becomes true (average velocity, standard projectile weights), then it becomes false again, as you cannot just keep adding 1,000 psi to the system and keep yielding a quieter muzzle report, it would be hard to achieve a quieter muzzle report at 30 fpe from a standard 20" barrel with 10,000 or 30,000 psi than it would be with 3,000 psi, for example, however it would be easier to achieve at 3,000 psi than it is at 2,000 psi
-Matt
-Matt
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