Adrien Mamou-Mani

Investigating the consistency of woodwind instrument manufacturing by comparing five nominally identical oboes

For large-scale woodwind instrument makers, producing instruments with exactly the same playing characteristics is a constant aim. This paper explores manufacturing consistency by comparing five Howarth S10 student model oboes. Psychophysical testing involving nine musicians is carried out to investigate perceived differences in the playing properties of the two Howarth oboes believed to be most dissimilar. Further testing, involving one musician and combinations of the five oboes, provides information regarding the relative playabilities of the instruments at specific pitches. Meanwhile, input impedance measurements are made on the five oboes for fingerings throughout the playing range and their bore profiles are measured. The main findings are (1) the two instruments used in the preliminary psychophysical testing are perceived as identical by most of the musicians, although differences are identified by two players when playing the note F6 and by one player when playing in the lowest register, (2) a variation in the playability of F6 across the five oboes is due to differences in the elevation of the C key, and (3) variations in the playing properties in the lowest register are related to input impedance differences,which, in turn, appear to be at least partly due to bore profile differences.

Prestressed Soundboards: Analytical Approach Using Simple Systems Including Geometric Nonlinearity

String instruments makers introduce prestresses on soundboards by adjusting the contact between the strings and the soundboard (downbearing). The effects of these prestresses on the vibration of the soundboard are investigated analytically, using a simple system of rods (one degree of freedom) and a buckled beam under the first two modes. For these two systems, we present successively the evolution of the eigenfrequencies and the nonlinear dynamical properties (phase diagrams, backbone curves). The two main results are 1) the second order evolution of the eigenfrequencies with prestresses are in agreement with a previous numerical simulation on a soundboard with the hypothesis of static large displacements and 2) the nonlinear dynamical properties of the system are modified by prestresses, and a prestressed soundboard working with large displacements seems to be technically possible.

A single microphone capillary-based system for measuring the complex input impedance of musical wind instruments

Capillary-based systems for measuring the input impedance of musical wind instruments were first developed in the mid-20th century and remain in widespread use today. In this paper, the basic principles and assumptions underpinning the design of such systems are examined. Inexpensive modifications to a capillary-based impedance measurement set-up made possible due to advances in computing and data acquisition technology are discussed. The modified set-up is able to measure both impedance magnitude and impedance phase even though it only contains one microphone. In addition, a method of calibration is described that results in a significant improvement in accuracy when measuring high impedance objects on the modified capillary-based system. The method involves carrying out calibration measurements on two different objects whose impedances are well-known theoretically. The benefits of performing two calibration measurements (as opposed to the one calibration measurement that has been traditionally used) are demonstrated experimentally through input impedance measurements on two test objects and a Boosey and Hawkes oboe.

Experimental Demonstration of the Modification of the Resonances of a Simplified Self-Sustained Wind Instrument Through Modal Active Control

This paper reports the experimental results of modifying the resonances of wind instruments using modal active control. Resonances of a simplified bass clarinet without holes (a cylindrical tube coupled to a bass clarinet mouthpiece including a reed) are adjusted either in frequency or in damping in order to modify its playing properties (pitch, strength of the harmonics of the sound, transient behaviour). This is achieved using a control setup consisting of a co-located loudspeaker and microphone linked to a computer with data acquisition capabilities. Software on the computer implements an observer (which contains a model of the system) and a controller. Measuring and adjusting the transfer function between the speaker and microphone of the control setup enables modifications of the input impedance and the radiated sound of the instrument.

SIMULATIONS OF MODAL ACTIVE CONTROL APPLIED TO THE SELF-SUSTAINED OSCILLATIONS OF THE CLARINET

This paper reports a new approach to modifying the sound produced by a wind instrument. The approach is based on modal active control, which enables adjustment of the damping and the frequencies of the different resonances of a system. A self-sustained oscillating wind instrument can be modeled as an excitation source coupled to a resonator via a non-linear coupling. The aim of this study is to present simulations of modal active control applied to a modeled self-sustained oscillating wind instrument in order to modify its playing properties. The modeled instrument comprises a cylindrical tube coupled to a reed and incorporates a collocated loudspeaker and microphone; it can thus be considered to approximate a simplified clarinet. Modifications of the pitch, the strength of the harmonics of the sound produced by the instrument, and of the oscillation threshold are obtained while controlling the first two resonances of the modeled instrument.

Prestress effects on the eigenfrequencies of the soundboards: experimental results on a simplified string instrument.

This paper presents an experimental study of the effects of prestresses on the vibration behavior of string instruments. These prestresses are created by gluing ribs (crowning) and tensioning string (downbearing). The effects of these prestresses were previously studied numerically for a piano soundboard by Mamou-Mani et al. [J. Acoust. Soc. Am. 123, 2401-2406 (2008)] and analytically for simplified models by Mamou-Mani et al. [Acta Acust. Unit. Acust. 95, 915-926 (2009)]. In the present study, a specified test bench is designed, including a simplified soundboard (a rectangular plate), a bridge, and a single string. The plate is subjected to in-plane and transverse loads. Vibrational eigenmodes are identified using nearfield acoustical holography (NAH) measurement. The evolution of eigenfrequencies with these specific prestresses is studied. The results show the effectiveness of NAH for this purpose and a very good qualitative concordance with previous numerical and analytical calculus.

Active control and sound synthesis—two different ways to investigate the influence of the modal parameters of a guitar on its sound

The vibrational behavior of musical instruments is usually studied using physical modeling and simulations. Recently, active control has proven its efficiency to experimentally modify the dynamical behavior of musical instruments. This approach could also be used as an experimental tool to systematically study fine physical phenomena. This paper proposes to use modal active control as an alternative to sound simulation to study the complex case of the coupling between classical guitar strings and soundboard. A comparison between modal active control and sound simulation investigates the advantages, the drawbacks, and the limits of these two approaches.

An active mute for the trombone

A mute is a device that is placed in the bell of a brass instrument to alter its sound. However, when a straight mute is used with a brass instrument, the frequencies of its first impedance peaks are slightly modified, and a mistuned, extra impedance peak appears. This peak affects the instruments playability, making some lower notes difficult or impossible to produce when playing at low dynamic levels. To understand and suppress this effect, an active mute with embedded microphone and speaker has been developed. A control loop with gain and phase shifting is used to control the damping and frequency of the extra impedance peak. The stability of the controlled system is studied and then the effect of the control on the input impedance and radiated sound of the trombone is investigated. It is shown that the playability problem results from a decrease in the input impedance magnitude at the playing frequency, caused by a trough located on the low frequency side of the extra impedance peak. When the extra impedance peak is suppressed, the playability of the note is restored. Meanwhile, when the extra impedance peak is moved in frequency, the playability problem position is shifted as well.

Modal active control applied to simplified string musical instrument

This study aims to control the vibrational eigenmodes of soundboards in order to modify the timbre of string instruments. These structures are wooden plates of complex shape, excited by a string through a bridge. Their modal parameters are first identified using modal analysis algorithms on experimental measurements. Then a digital controller is designed using these parameters and classic active control methods. The effects of this controller are first studied thanks to time simulation. Prior to applying experimentally this controller, an optimization procedure is carried out to determine the quantity, dimensions and positions of sensors and actuators needed for the control. These best possible specifications are obtained according to the controllability, observability and other optimization criteria. Finally, a real time system using the control procedure is tested on a simplified musical instrument. The experiment is conducted on a rectangular spruce plate, clamped at its boundary and excited by means o...

Active control applied to simplified wind musical instrument

Active control is widely used in industry. However, there have been relatively few applications to musical instruments, particularly wind instruments. The aim of this study is to attempt to control the sound quality and playability of wind instruments, using active control. Active control makes it possible to modify the input impedance (amplitude and frequency) of an instrument and to modify the instruments quality. Simulations and first experiments on a cylindrical tube, which is considered to be a simple wind instrument, with embedded microphone and speaker are presented. Finally, the effects on the sound and the input impedance of the instrument are studied.