Received an e-mail from a reader asking if I was opposed to sound meter measurements.

The short answer is NO.

 I am not opposed to that practice; however, I think the methodology used is flawed; were I designing a test scenario, my approach would be significantly different.

• I would set up a test environment using nothing more than a chambered barrel  of the following lengths for a 5.56×45 can: 10.5″ 14.5″ 16″ 20″ for  7.62×51 : 18″ 20″ 24″ 26″. This eliminates any action related noise so the suppressor is isolated for the measurement.
• All testing would be done in an anechoic chamber.
• I would fire 5 groups of 10 rounds each through each barrel. I would also measure the results with and without a suppressor installed, using the appropriate mounts. The reason for at least 10 data points is to be able to perform a normal statistical analysis.
• If I were testing just for the military I would use their specific ammunition, for example M855A1, M80 or M118LR.
• I would tabulate the suppressed and unsuppressed results for each of the barrel lengths and provide the following data:
  1. Cartridge.
  2. Barrel Length.
  3. Unsuppressed measurement: db (SPL) ±  (computed using normal statistics).
  4. Suppressed measurement: db (SPL) ± (computed using normal statistics)
  5. Sound attenuation: (Unsuppressed – Suppressed) expressed in dB.