Future lumber characteristics depend on the quality of the log. Stress wave velocity is a good predictor of log quality, as it largely influences the dynamic MOE (calculated as the product of density and stress-wave velocity squared).
The Resonance Log Grader is a simple tool. It consists of a hammer and an Android phone or tablet with a specialised software. The user enters the length, then hits the end of the log. The accurate velocity appears on the screen and a grade is assigned based on the results.