We spent a lot of time testing our suppressors. We used a Larson Davis LXT1-QPR and all numbers provided are at the shooters ear. We found a few things interesting. For instance, just closing the bolt on our M4 was 136 dB, the 10/22 was 112 dB. The hammer falling on the 10/22 was 106 dB. The gas operated M4 and AR15 were about 6 dB louder than the bolt action counterparts. Some can be explained by the action noise was 136 dB and the direct impingement system venting gasses into the action. OSHA standard for impulse noise is 140 dB.