Is nonlinear propagation responsible for the brassiness of elephant trumpet calls?

African elephants (Loxodonta africana) produce a broad diversity of sounds ranging from infrasonic rumbles to much higher frequency trumpets. Trumpet calls are very loud voiced signals given by highly aroused elephants, and appear to be produced by a forceful expulsion of air through the trunk. Some trumpet calls have a very distinctive quality that is unique in the animal kingdom, but resemble the "brassy" sounds that can be produced with brass musical instruments such as trumpets or trombones. Brassy musical sounds are characterised by a flat spectral slope caused by the nonlinear propagation of the source wave as it travels through the long bore of the instrument. The extent of this phenomenon, which normally occurs at high intensity levels (e.g. fortissimo), depends on the fundamental frequency (F0) of the source as well as on the length of the resonating tube. Interestingly, the length of the vocal tract of the elephant (as measured from the vocal folds to the end of the trunk) approximates the critical length for shockwave formation, given the fundamental frequency and intensity of trumpet calls. We suggest that this phenomenon could explain the unique, distinctive brassy quality of elephant trumpet calls

Transients in porous media: asymptotic time-domain Green functions and limits of current frequency-domain models

Time domain responses of porous media have been studied by some authors, but generally the possible descriptions have been given in the frequency domain. The aim of this paper, limited to materials with rigid skeleton considered as equivalent fluids, is to compare the descriptions by Johnson-Allard ($JA$%) as well as by Pride-Lafarge ($PL$) with i) some analytical, approximate formulas, based upon asymptotic high frequency expansion ; ii) the exact formula by Zwikker and Kosten for the case of cylindrical pores. The paper starts with a short summary of the statement of the different general full frequency models ($JA$ and $PL).$ The Green function in the time domain is shown to exhibit interesting properties of materials. In particular the maximum response depends on one dimensionless parameter only, which is denoted $\xi$ and is the ratio of the travelled distance to the product of the \textquotedblleft frozen\textquotedblright\ sound speed and a characteristic viscous relaxation time. The distance $\xi$ is related to a time domain Stokes number. The numerical computation of the Green function is done by FFT, with some precautions, because of the importance of the higher frequencies on the response shape. The $PL$ description is shown to be the best full frequency general model, but some discrepancies with the exact model appear at short times or short distances. When the distance $\xi$ increases from zero, the asymptotic expansion shows that the maximum of the Green function decreases first as $1/\xi ^{2}$, then exponentially

From the bifurcation diagrams to the ease of playing of reed musical instruments. A theoretical illustration of the Bouasse-Benade prescription?

International audienceReed musical instruments can be described in terms of conceptually separate linear and nonlinear mechanisms: a localized nonlinear element (the valve effect due to the reed) excites a linear, passive acoustical multimode element (the musical instrument usually represented in the frequency domain by its input impedance). The linear element in turn influences the operation of the nonlinear element. The reed musical instruments are self-sustained oscillators. They generate an oscillating acoustical pressure (the note played) from a static over-pressure in the player's mouth (the blowing pressure). A reed instrument having N acoustical modes can be described as a 2N dimensional autonomous nonlinear dy-namical system. A reed-like instrument having two quasi-harmonic resonances, represented by a 4 dimensional dynamical system, is studied using the continuation and bifurcation software AUTO. Bifurcation diagrams are explored with respect to the blowing pressure, with focus on amplitude and frequency evolutions along the different solution branches. Some of the results are interpreted in terms of the ease of playing of the reed instrument. They can be interpreted as a theoretical illustration of the Bouasse-Benade prescription

Comparative Analysis of Brass Wind Instruments With an Artificial Mouth: First Results

International audienceWe have developed in the past “artificial mouths” to study the behaviour of brass wind instruments (trumpet, trombone) in the playing situation, but without a musician. After using such devices to better understand the physical phenomena involved in brass instruments, we have built and used a new artificial mouth with the objective to test and set up instruments; the artificial mouth is considered here as a “test bench”. In this article, we describe the typical measurements that we have carried out on trumpets, in order to compare them (measurements of oscillation threshold, evolution of the playing frequency according to the dynamic level). As a first result, the artificial mouth allows one to show noticeable differences between instruments. We propose next some research paths which could be explored in order to better control the quality of instruments and, in the future, to introduce the use of an artificial mouth in the design process of brass instruments

How far can the resonance frequencies give informations about the playing frequencies? The trumpet example

International audienceMeasurements and calculations of the input impedance of wind musical instruments are now well mastered. The purpose of this work is to study experimentally how far the resonance frequencies of brass instruments, taken from their input impedance, are able to give informations about the playing frequencies. Three different trumpets, obtained by changing only the leadpipe of the same instrument, were considered for the experiment. After a measurement of the input impedance of these trumpets, four musicians were asked to play the five first playable notes (regimes 2 to 6), for four different fingerings. This exercise was done for three nuances and was repeated three times. Finally, these 3×4×5×4×3×3=2160 notes allow us to make a quantitative assessment of the relations between the resonance frequencies and the playing frequencies. Results show first, a limited influence of the musician on the overall intonation of the instrument. Second, the pitch of the notes does not vary much with the nuances. Finally, the results confirm the fact that variations of the resonance frequencies lead to variations of the playing frequencies of the same order

Termination impedance of open-ended cylindrical tubes at high sound pressure level

International audienceThe study deals with nonlinear acoustical effects localised at the open-end of a cylindrical tube. The termination impedance is measured using a two microphone method. Due to the separation of the acoustic flow at the pipe end, the real part of the termination impedance depends on the volume velocity at the open end. It is shown that the radius of curvature of the edges of the open end of the tube has a crucial influence on the amplitude of the nonlinear losses. Several regimes are shown for the low radii of curvature

Diversity of ghost notes in tubas, euphoniums and saxhorns

The ghost note is a natural note which can be played exclusively on bass brass instruments with a predominantly-expanding bore profile such as tubas, euphoniums or saxhorns. It stands between the pedal note-the lowest natural note playable, or first regime-and the instrument's second regime. However, if the interval between the pedal note and the second regime remains close to an octave regardless of the instrument, the interval between the pedal note and the ghost note vary from a minor third to a perfect fourth. References about this note are very scarce, and it is not commonly known among tuba players.This study shows that an elementary brass model describing the player coupled to the instrument is capable of bringing both the ghost and the pedal note to light. Here, we adopt a dynamical systems point of view and perform a bifurcation analysis using a software of numerical continuation. The numerical results provided in terms of frequency intervals between pedal note and ghost note are compared with frequency intervals experimentally inferred from recordings of seven different types of tuba, each of them being played by two professional tuba players.Comment: arXiv admin note: text overlap with arXiv:2112.0875

Effect of actual and accelerated ageing on microstructure evolution and mechanical properties of a 2024-T351 aluminium alloy

This paper presents an investigation on the effects of ageing on the microstructure and the corresponding physical and mechanical properties of a 2024 aluminium alloy used in a civil transport aircraft wing structure in order to assess the residual resistance of the end of a service life. More precisely, heat treatments are applied in order to simulate thermal ageing actually endured by the structure during service. The results of characterisation of microstructural, physical and mechanical properties are compared not only to the data obtained on a pristine alloy, but also to the results obtained on coupons of a similar alloy coming from the teardown of an A320 aircraft using the same experimental procedure. The main findings are that, during a service life, no significant modification in fatigue resistance is noticed despite of changes in the precipitation structure

Interaction of reed and acoustic resonator in clarinetlike systems

Sound emergence in clarinetlike instruments is investigated in terms of instability of the static regime. Various models of reed-bore coupling are considered, from the pioneering work of Wilson and Beavers ["Operating modes of the clarinet", J. Acoust. Soc. Am. 56, 653--658 (1974)] to more recent modeling including viscothermal bore losses and vena contracta at the reed inlet. The pressure threshold above which these models may oscillate as well as the frequency of oscillation at threshold are calculated. In addition to Wilson and Beavers' previous conclusions concerning the role of the reed damping in the selection of the register the instrument will play on, the influence of the reed motion induced flow is also emphasized, particularly its effect on playing frequencies, contributing to reduce discrepancies between Wilson and Beavers' experimental results and theory, despite discrepancies still remain concerning the pressure threshold. Finally, analytical approximations of the oscillating solution based on Fourier series expansion are obtained in the vicinity of the threshold of oscillation. This allows to emphasize the conditions which determine the nature of the bifurcation (direct or inverse) through which the note may emerge, with therefore important consequences on the musical playing performances

321. Deletion of Mutated GAA Repeats from the Intron 1 of the Frataxin Gene Using the CRISPR System Restores the Protein Expression in a Friedreich Ataxia Model

The CRISPR system is now widely used as a molecular tool to edit the genome. We used this technique in Friedreich Ataxia (FRDA), an inherited autosomal disease known to cause a decrease of the mitochondrial frataxin protein. Genetic analysis revealed a GAA repeat expansion within the intron 1 of the frataxin (FXN) gene. We used cells derived from the YG8sR mouse model where the mouse frataxin gene is knockout but contain a human FXN mutated transgene on one allele. We then deleted the GAA trinucleotide repeat using 2 specific guide RNAs (gRNAs) co-expressed with either S. pyogenes (Sp) or S. aureus (Sa) Cas9. We were able to monitored an increase up to 2-fold of frataxin mRNA and protein levels in clone cells. We also confirmed these results in vivo using DNA electroporation in the Tibialis anterior muscle of the YG8R mice. Ongoing in vivo investigation of a systemically injected AAV-DJ vector expressing the SaCas9 and 2 successful selected gRNAs in the mouse model YG8sR will hopefully provide more details answers on the efficacy of the approach and give us preliminary data to go forward for clinical trial. The deletion of the GAA repeats expansion then might be a highly valuable gene therapy approach for FRDA patients