scholarly journals Peak-picking identification technique for modal expansion of input impedance of brass instruments

Acta Acustica ◽  
2021 ◽  
Vol 5 ◽  
pp. 53
Author(s):  
Frédéric Ablitzer

The paper presents a method to obtain the modal expansion of the measured input impedance of a brass instrument. The method operates as a peak-picking procedure, which makes it particularly intuitive for users who are not experts in modal analysis. To bypass the limitation of usual peak-picking approaches, which are valid only for well separated resonances, the present method is based on a semi-local optimization problem. It consists in adjusting the frequency and damping of one mode at a time while taking into account the presence of all other modes in the basis. The practical application of the method involves four elementary actions, which can be chained in different ways to progressively approximate a measured input impedance. This procedure is illustrated through the approximation of the input impedance of a bass trombone. The supervised nature of the method allows the user to favour modes that have a physical meaning, i.e. that can be associated with a resonance peak. A single spurious mode can however be deliberately introduced to approximate the input impedance curve beyond the last visible peak. The method applies directly to the frequency-domain data provided by an impedance sensor and does not require any preprocessing. Nevertheless, it is fairly robust to noisy data. Since the method allows a reconstruction of the input impedance using either complex modes or real modes, results obtained with each approximation are critically compared.

1989 ◽  
Vol 256 (6) ◽  
pp. H1684-H1689 ◽  
Author(s):  
K. B. Campbell ◽  
L. C. Lee ◽  
H. F. Frasch ◽  
A. Noordergraaf

The concept of effective length (L) of the arterial system implies that it may be represented by a single viscoelastic tube terminated by an impedance, creating a single reflection site. Although the concept is straightforward, investigators for years have been unable to agree on the value of L. Proposed values range from a few millimeters to a few meters, confounding the identification of arterial reflection sites. This report shows analytically and illustrates with experimental data that the determination of the effective length leaves room for an infinite number of exact solutions for L and the corresponding terminal impedance if the input impedance of the tube is to match the measured input impedance of an arterial system. None of the possible values of L needs to bear any relationship to actual reflection sites.


2014 ◽  
Vol 8 (1) ◽  
pp. 279-284
Author(s):  
Qinghua Cao ◽  
Dingfang CaoChen ◽  
Quanguo Lu ◽  
Jianwu LuYan ◽  
Gang Tang ◽  
...  

This paper aims to designed a prototype for achieving the full magnetostriction of Galfenol, Lamination struction of transducer is designed and the radiation impedance is expressed in mechanical terms, a simplified onedimensional modeling of SPICE magnetostrictive transducer is established, the electrical input impedance is simulated as the function of frequency and experimentally adjusting the values is to match an existing impedance curve. a good fit between model and measurement is shown by measured and simulated electrical input impedances for the device.


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