51 research outputs found
The logical clarinet: numerical optimization of the geometry of woodwind instruments
The tone hole geometry of a clarinet is optimized numerically. The instrument
is modeled as a network of one dimensional transmission line elements. For each
(non-fork) fingering, we first calculate the resonance frequencies of the input
impedance peaks, and compare them with the frequencies of a mathematically even
chromatic scale (equal temperament). A least square algorithm is then used to
minimize the differences and to derive the geometry of the instrument. Various
situations are studied, with and without dedicated register hole and/or
enlargement of the bore. With a dedicated register hole, the differences can
remain less than 10 musical cents throughout the whole usual range of a
clarinet. The positions, diameters and lengths of the chimneys vary regularly
over the whole length of the instrument, in contrast with usual clarinets.
Nevertheless, we recover one usual feature of instruments, namely that
gradually larger tone holes occur when the distance to the reed increases. A
fully chromatic prototype instrument has been built to check these
calculations, and tested experimentally with an artificial blowing machine,
providing good agreement with the numerical predictions
1,4-Bis(methylÂsulfanÂyl)naphthalene
The molÂecule of the title compound, C12H12S2, is close to planar, with the methyl C atoms deviating by 0.019â
(1) and 0.221â
(2)â
Ă
from the naphthalene mean plane. In the crystal structure, the shortest SâŻS contact of 3.6864â
(9)â
Ă
is longer than the van der Waals contact distance
Nonlinear modes of clarinet-like musical instruments
The concept of nonlinear modes is applied in order to analyze the behavior of
a model of woodwind reed instruments. Using a modal expansion of the impedance
of the instrument, and by projecting the equation for the acoustic pressure on
the normal modes of the air column, a system of second order ordinary
differential equations is obtained. The equations are coupled through the
nonlinear relation describing the volume flow of air through the reed channel
in response to the pressure difference across the reed. The system is treated
using an amplitude-phase formulation for nonlinear modes, where the frequency
and damping functions, as well as the invariant manifolds in the phase space,
are unknowns to be determined. The formulation gives, without explicit
integration of the underlying ordinary differential equation, access to the
transient, the limit cycle, its period and stability. The process is
illustrated for a model reduced to three normal modes of the air column
Vad sjöng folk pÄ Orust? : En studie av Martin Martinsson och hans folkviserepertoar
Martin Martinsson var en folksÄngare pÄ Orust i BohuslÀn. Syftet med uppsatsen Àr att studera sÄngaren pch hans repertoar och att dÀrmed belysa en viktig del av den bohuslÀnska folkmusikskatten. En beskrivning görs av BohuslÀn och Orust som bakgrund och miljö för vistraditionen. Slutsatsen som kan dras av uppsatsen Àr att Martin Martinsson blev en kÀnd folkvisesÄngare av tillfÀlligheter som hÀngde ihop med musikforskarnas intresse för folkmusiken i BohuslÀn
Vad sjöng folk pÄ Orust? : En studie av Martin Martinsson och hans folkviserepertoar
Martin Martinsson var en folksÄngare pÄ Orust i BohuslÀn. Syftet med uppsatsen Àr att studera sÄngaren pch hans repertoar och att dÀrmed belysa en viktig del av den bohuslÀnska folkmusikskatten. En beskrivning görs av BohuslÀn och Orust som bakgrund och miljö för vistraditionen. Slutsatsen som kan dras av uppsatsen Àr att Martin Martinsson blev en kÀnd folkvisesÄngare av tillfÀlligheter som hÀngde ihop med musikforskarnas intresse för folkmusiken i BohuslÀn
ChemInform Abstract: Structure of the Organic Semiconducting Radical Cation Salt Tris(2,6- dimethoxy-3,7-bis(methylthio)naphthalene) Diperchlorate.
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