New paper by Lincoln university.
"The effect of back wood choice on the perceived quality of steel-string acoustic guitars" / The Journal of the Acoustical Society of America 144, 3533 (2018);

Study by Samuele Carcagno, Roger Bucknall, Jim Woodhouse, Claudia Fritz, and Christopher J. Plack).

The results of our study indicate that steel-string acoustic guitars with backs and sides built using traditionally prized, expensive, and rare woods are not rated substantially higher by guitarists than guitars with backs and sides built using cheaper and more readily available woods. The poor ability of guitarists to discriminate under blinded conditions between guitars with backs and sides made of different woods suggest that back wood has only a marginal impact on the sound of an acoustic guitar.
link to the publication

François Gautier (Professor in Acoustics / vibrations University of Maine Acoustics Laboratory) will present his study with 16 'Leonardo' guitars at 26th International Congress on Sound and Vibration (ICSV26)

(https://www.iiav.org/icsv26/) to be held in Montréal 7–11 July 2019.
Stydy by F. Gautier, F. Ablitzer, M. Curtit,
J. Walraet, M. Gozzini, L .Brillon, A. Brunet.

Summary of the presentation:
Platform for sound and vibration analysis in the string instrument maker’s workshop : case of the Leonardo Guitar Research Project.

Analyzing acoustic features of a string musical instrument is possible in an acoustic lab context using appropriated techniques and equipment. However, adapting sound and vibration analysis techniques to the specific context of an instrument maker’s workshop is challenging: a collaborative approach involving makers and acousticians has permitted the development of a software and hardware platform called PAFI, (Plateforme d’Aide à la Facture Instrumentale). PAFI is an on line software platform comprising a modal analysis tool, a sound synthesis environment based on a hybrid model and the access to a database of measurements made on string instruments. PAFIBOX is the hardware kit associated to this system (acquisition card / accelerometer / microphone). PAFI is tested by a small community of makers including 3 schools of lutherie(Ecole Bruand in Montréal-Canada, CMB in Puurs-Belgium, ITEMM in Le Mans-France).

The aim of the paper is to present several tests cases performed on the platform, which reveals the expectations of the instruments makers. The attention is focused on the example of the European project Leonardo, whose goal is to analyze if the presence of tropical woods induces a particular acoustic signature in the classical guitars. Pairs of guitars made with identical geometrical characteristics, but with tropical and non-tropical woods were produced and systematic sound recordings and mobility measurements were performed.
Since direct listening tests and blind comparisons do not identify specificities in a clear way, a methodology is proposed to analyze the discrepancies between instruments: sound synthesis is performed using a hybrid model mixing an analytical description of the string vibrations and an experimental modal analysis at the coupling point. Such an approach guaranties that strings and gesture are strictly identical in all compared sounds. Statistical results obtained from the PAFI database will be presented.

The Leonardo Guitar Research Project (LGRP)

is a non-profit organization whose purpose is to

study, demonstrate and communicate the possibilities of building acoustic and classical guitars from non-tropical woods. 

The LGRP was funded from 2012 till 2014 by the 'Leonardo da Vinci Programme', and from 2014 till 2017 by Erasmus+, both programmes of the European Commission.

The LGRP Partner Group consists of lutherie schools, independent luthiers, researchers, experts and organisations in the field of musical instruments

TEASER: one of the LGRP studies;  a (blind) online test with 16 guitars

In this video Gaëlle Solal plays 16 guitars who were recorded and edited into sections of the desired length and then pasted together into one musical piece.

Eight guitars are made from traditionally used tropical woods like rosewood, ebony, mahogany and Spanish Cedar.

Eight guitars are made from local and non-commonly used non-tropical woods..

The guitars were made by eight builders. Each builder made a pair of guitars consisting of one made from tropical woods and one made from non-tropical woods. The pairs appear consecutively in the track.

All guitars are of the same model. They all have European spruce tops, the same bracing pattern and the same strings. They are recorded with a flat EQ. No audio editing or effects are added.

This video was part of a blind listening test.

The audio of this  video was used for a (blind) online listening survey which was running from 08.06.17 until 26.06.2017 and was completed by 226 respondents worldwide.

The survey asked questions such as:

- How many guitars did you perceive ?

- Can you note the transition time points (when one guitar follows another) ?

- How many of the perceived guitars are made from non-tropical wood species?

The chart below shows the woods used  per guitar for back/sides, neck, fingerboard and bridge

Guitar neck stability and
stiffness tests

Follow-up research by the University of Ghent / Theses of Pieter Goovaerts,

Master of Science in Bioengineering: Forest and Nature Management.

Testing non tropical woods for suitability as Fingerboards, pdf