Here DB Noise level of my SV-17cc engine while standing on top of the plane with the meter about 5 feet away from the engine. This is with my homemade baffle insert installed in the muffler. Now normally they measure the DB noise level while standing at about ten feet from the muffler side of the engine, while the engine is at WOT. Also you have the plane on a table test stand about 30 inches above the ground level too.
Without the insert the DB noise level is about 100db or a touch more.
If I held the DB meter at about 3 feet above the engine, the DB noise level goes up a little more. But it is still within the 95db max club rules at our flying field.