Methods for determining velocity of a stress wave within a material and homogeneity of properties within the material

A method for evaluating homogeneity of properties within a material, the method comprising the steps of:

• inducing a stress wave into the material;
• measuring a distance traveled by the stress wave along the material;
• measuring a time of travel of the stress wave across the distance;
• determining a first velocity associated with the stress wave by dividing the distance by the time of travel;
• obtaining resonance measurements of the material after the stress wave is induced;
• subjecting the resonance measurements to an algorithm to determine a fundamental frequency of the stress wave;
• determining a second velocity associated with the stress wave based on the determined fundamental frequency;
• and
• comparing the first velocity to the second velocity wherein a difference between the first velocity and the second velocity is an indication of the homogeneity of properties of the material.

A method for determining a velocity of a wave within a wood product based on resonance measurements, the method comprising the steps of:

• inducing a stress wave into the wood product at a time t1;
• measuring a first amplitude created at the time t1;
• measuring a second amplitude at a time t2 caused by travel of the stress wave through the wood product;
• measuring a distance traveled by the stress wave within the wood product in a period of time between the time t2 and the time t1;
• determining a first velocity of the stress wave by dividing the distance traveled by the stress wave by the period of time between the time t2 and the time t1;
• obtaining resonance measurements of the wood product after the time t1;
• subjecting the resonance measurements to a Fast Fourier Transform algorithm to provide a plurality of candidate values for a second velocity of the stress wave, the second velocity being a velocity of the stress wave based on resonance measurements;
• and
• selecting a most accurate candidate value from the plurality of candidate values based on its proximity to the first velocity wherein the most accurate candidate value is considered the second velocity.