I notice from your other videos that you don't seem to have dB readings over 83, regardless of moderator, or meter placement. This makes me wonder if you are near the maximum reading the meter can measure. If so, the readings near that level are probably not very linear. In other words, a significantly quieter mod may only measure slightly lower dB.
To test this, measure the bare muzzle dB also. If that is not much over 83 dB, then the meter may not be providing good readings.
To avoid running too close to maximum dB that the meter can measure, use comparative measurements from further away. The readings should drop according to the inverse square law for radiating sound. In other words, doubling the distance should lower the same airgun/mod/tune/peller sound reading by 6 dB, This should happen if you double the distance again; and again. If it does not, then something is fishy. If this 6 dB drop for doubling the distance only starts reliably at 10 feet from the muzzle, then closer measurements are suspect.
The industry standard distance is 1 meter to the side of the muzzle, with the muzzle something like 1.5 meter off the ground. But if you meter is not capable, or is not calibrated then your measurements are likely not going to be the same as a "standard" meter.
If you get a bare muzzle reading of 92 dB or higher, from the same meter distance as your mod testing, that would be a good start. This assumes the bare muzzle reading sounds loud to your ear. If you have a very good shroud system on your PCP, adding mods may not make much of a difference. Whereas, a direct to barrel attachment may show a larger difference between mods.
When a person reports an apparent doubling or halving of sound heard by ear, that is around a 10 dB actual difference. In other words, while people notice a 3 dB difference, they may not be impressed by it.
