10H50 : n° 379 Propriétés vibratoires viscoélastiques des bois en direction axiale : distributions et analyses sur 450 espèces ligneuses

Iris Brémaud
Laboratory of Forest Resource Circulating Circles
On présente une collection de données sur les propriétés vibratoires viscoélastiques de 450 espèces ligneuses, en réponse au manque actuel de vision globale notamment sur les coefficients d’amortissement. Les données proviennent de nos travaux expérimentaux et d’une revue exhaustive de la littérature. Les résultats présentés comprennent : les distributions de propriétés vibratoires par grands groupes ; des exemples de relations avec la phylogénie ; des applications aux instruments de musique.

11H10 : n° 756 Acoustic quality of vène wood (Pterocarpus erinaceus Poir) for xylophones instruments manufacture in Mali

Bakary Traoré Loïc Branchériau Patrick Perré Tatjana Stevanovic Papa Diouf
CRB (Centre de Recherche sur le Bois) Université Laval
Xylophone belongs to the idiophone group of instruments which is very present in the African traditional and popular music. Its sound percussion quality is related to the resonance and the intrinsic properties of used wood. In spite of numerous studies of the acoustic properties of wood, very few works are available on Pterocarpus species in general and notably on Pterocarpus erinaceus. In this study, the variability of acoustic properties of vène (Pterocarpus erinaceus Poir), used for xylophone instrument manufacture in Mali and the relationships between these properties and the basic density and extractive content were investigated in order to provide information about its overall suitability for xylophone making. A free-free flexural method, known as “Bing”, was used to determine the main mechanical properties for the xylophone instrument manufacture i.e. the damping coefficient and the specific dynamic modulus while the basic density and the extractives (EC) content were determined according to international standards ISO 3129 and ASTM D1105 (1996), respectively. The results showed that the dynamic specific modulus, the basic density and the extractive content are significantly higher for wood from Guinean area than for wood from Soudanian area. For all provenances the values determined for these properties have been significantly higher for wood from external (EHW) and median heartwood (MHW) than for wood from internal heartwood (IHW). The damping coefficient, the loss factor is significantly greater for wood from Soudanian area than for wood from Guinean area, and regardless of provenance, the loss factor was significantly greater for wood from IWH than in MHW and EHW.

11H30 : n° 427 Mesure de la viscoélasticité du bois sur la gamme audio. Applications à la lutherie.

Marc François Sandie Le Conte
FAST
La mesure de l'angle de perte est obtenue par le déphasage du signal au travers du montage dont la structure est analogue à une ligne à retard. La conception anirésonnante autorise une mesure sur la gamme audio via l'émission d'un chirp. De plus, la variation de l'angle de perte au cours du temps, pour une fréquence d'excitation maintenue, est identifiée.

11H50 : n° 1352 Effect on viscoelasticity measurement of wood pest control: application to musical instruments

Sandie Le Conte Emmanuel Maurin
Lab. de Recherche et de Restauration du Musée de la Musique
Some of our museum collection musical instruments belong to the strings instrument family and are made of wood. The aim of this study is to measure the viscoelasticity properties of wood under a strain field in the audio frequency range knowing that viscoelasticity seems to be deeply involved in the quality of sound and structure stability. We want to evaluate the effect on the viscoelasticity of the freezing and the microwave using for wood pest control.