Analyse expérimentale de l'effet de l'inharmonicité des instruments a anche simple -Cas du saxophone alto

National audiencePour les instruments de musiquè a vent, l'inharmonicité des fréquences de résonance est une des grandeurs considérées , en facture instrumentale, comme représentatives de la qualité d'un instrument. L'inharmonicité peut altérer le timbre ainsi que la justesse de l'instrument. Pour les saxophones, l'inharmonicité des fréquences de résonances est principalement causée par la troncature de la perce conique ainsi que par la présence des trous latéraux. Le but de ce travail est de mettre en avant expérimentalement l'effet de l'inharmonicité des fréquences de résonances sur la nature des régimes d'oscillation produits par un instrument a anche simple. Un piston est fixé au niveau du bocal d'un saxophone alto afin de diminuer progressivement lapremì ere fréquence de résonance , ce qui permet de modifier l'inharmonicité de l'instrument. Une bouche artificielle est utilisée afin de mettre en oscillation l'instrument avec des param etres de contrôle constants (param etre d'embouchure et pression statique dans la bouche). Ces param etres sont evalués expérimentalement par le biais d'une mesure de la caractéristique non linéaire. Par modification des param etres de contrôle et de l'inharmonicité, une grande diversité de régimes d'oscillation est observée expérimentalement. Ces régimes sont identifiés par l'analyse du signal de pression a l' intérieur du bec. En particulier, des régimes d'oscillation quasi-périodiques sont produits sous forme de sons multiphoniques

A Minimal Model of a Single-Reed Instrument Producing Quasi-Periodic Sounds

International audienceSingle-reed instruments can produce multiphonic sounds when they generate quasi-periodic oscillations. The aim of this article is to identify a minimal model of a single reed-instrument producing quasi-periodic oscillations. To better understand the influence of model parameters on the production of quasi-periodic regimes, the mapping between parameters and quasi-periodic regimes is explicitly identified using a support vector machine (SVM) classifier. SVMs enable the construction of boundaries between quasi-periodic and periodic regimes that are explicitly defined in terms of the parameters. Results and conclusions obtained from the numerical model are compared to published experiments related to the the production of quasi-periodic oscillations with an alto saxophone. This qualitative comparison highlights the influence of key parameters on the production of multiphonic sounds

Nature documentaries as catalysts for change: Mapping out the 'Blackfish Effect'

It is essential for us to understand what drives human behaviour if we want to tackle anthropogenic damage to the environment. Popular media can play an important role in shaping public attitudes, behaviours and norms towards wildlife, and documentaries in particular have become an increasingly prominent tool for social change. There is, however, a need for robust impact evaluation both in documentary-making and in conservation, to refine future interventions. The 2013 documentary Blackfish portrayed human–orca interactions at the US-based marine park, SeaWorld. Following its release, SeaWorld suffered financial difficulties and the company underwent structural changes, including a cessation of its orca breeding programme. These impacts have often been attributed to the Blackfish documentary, but little evidence has been provided to justify these claims. We combined an analysis of stock market data and semi-structured interviews with 26 key informants to build an in-depth contribution analysis. We used General Elimination Methodology, a qualitative impact evaluation methodology to build an understanding of the impact of Blackfish. We found a consensus among stakeholder groups that Blackfish induced negative publicity for SeaWorld and a change in people's perceptions of captivity. As a result, attendance at the park decreased and the market value of the company dropped. Blackfish catalysed a whole movement against marine mammal captivity. There were three key factors that led to its impact: the support from major distribution channels which allowed it to reach major audiences, emotional impact of the content and timing of its release. Blackfish benefitted from a perfect storm, building upon decades of activism to create an appropriate cultural climate for its release in 2013