Non-destructive assessment of wood properties in tree stems using acoustic imaging

There is significant interest in non-destructive testing of trees and felled logs. One way of imaging the interior of tree stems is using acoustic techniques. This paper describes a study which investigates the potential of acoustics for automatic detection of knots in felled logs for optimising the value that can be achieved during sawmilling. Pulses of sound, in the audio frequency range, were excited at one end of a log using an air-coupled transducer. The sound emitted from the log was then detected at a range of positions along the log using a single microphone in contact with the log and then using a non-contact acoustic camera. Initial results are presented which indicate that this technique may have potential as a means of automatically detecting knots. Results from current research, including the development and use of high power ultrasound, will be presented. Future research plans will then be outlined.