New Technical Note examines acoustic technology's potential for assessing timber properties

The Forestry Commission has published a new Technical Note about the use of acoustic tools in forestry and the wood supply chain.
 
It was written by Shaun Mochan and Dr Thomas Connolly from the Commission's Forest Research arm, and Dr John Moore from the Centre for Timber Engineering at Edinburgh Napier University.
 
There is a growing demand to use forest resources for a range of end uses. Because wood properties vary between and within trees and stands,  it is important that these properties are accurately assessed so that material can be directed to the most appropriate end use.
 
This Technical Note explains how acoustic technology can be used to predict the mechanical properties of timber (a practice common overseas) and that advances in technology, including the development of portable devices, have enabled the use of acoustic tools to make assessments of wood properties in standing trees and in felled logs.
 
It reports that research in the UK has shown that measurements of wood properties in standing trees and felled logs can be related to the mechanical properties in timber produced from them. This provides the possibility of classifying and sorting timber earlier in the wood supply chain, for example, within the forest, as well as further down the supply chain, for example, when it reaches the sawmill. The sooner the wood can be segregated, the more opportunity there is to efficiently direct it to the most suitable end use.
 
Current means of assessing timber properties are often inefficient, because timber is often transported to mills, processed and dried before its wood properties are determined. In addition, most segregation of trees and logs is currently undertaken by visual methods. Although effective for providing estimates of volume, visual assessment is less accurate for assessing the physical or mechanical properties of the wood. These physical and mechanical qualities are, however, critical in understanding whether it can be used for structural purposes. Current timber grading practices can result in additional economic and environmental costs because timber sometimes has to be down-graded after it has been processed and directed to alternative end uses, which may incur further transport costs.
 
The publication provides an explanation of how acoustic tools work, and examples of different tools and their possible uses. It explains that further research is needed to understand how results from different tools compare with the mechanical properties of the timber. This will enable the development of guidance on the thresholds for different end uses of timber according to each tool.
 
Trials are also under way to fit acoustic technology to harvester heads to enable trees to be assessed automatically as they are felled, and enable the operator to modify the cutting pattern according to the stiffness of the timber and its proposed end use.
 
A PDF version of this Technical Note, entitled "Using acoustic tools in forestry and the wood supply chain", can be downloaded from the "What's New" page of the publications section of the Forestry Commission website at www.forestry.gov.uk/publications.  Free paper copies can be ordered from Forestry Commission Publications, PO Box 25, Wetherby, West Yorkshire LS23 7EW; telephone: 0844 991 6500; fax: 0844 991 6501; email:
forestry@mrm.co.uk, quoting stock code FCTN018.
 
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