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Acoustical investigations on the ears of flue organ pipes

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The application of ears is one of the voicing techniques for flue organ pipes. The ears are the projections on both sides of the pipe mouth and have been used since the Renaissance period. They are frequently used to narrow scaled and low pitched pipes. By the structure around the mouth not only the radiation characteristics of the pipe but also the jet, the source of the pipe sound, will be influenced. Since the ears are attached to the mouth, their effect must be seen both in the sound and the jet. The aim of this research is to find out in details what kind of effect the ears have on the pipe sound and on the jet. According to the opinion of organ builders, the pipe sound will be lower and darker, and the build-up of the sound smoother and faster by attaching the ears. By our measurements, these recognitions were approved. The sound becomes more fundamental and the number of the harmonics is increased by adding the ears. Looking the growth of the harmonics in the attack transient, the attack time tends to be shorter and the attack becomes stable with the ears. In addition the previous investigations indicated an increase in the inharmonicity of the eigenmodes of the resonator due to the ears, and the existence of a proper value for the height of the ears was confirmed.
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This paper presents the usage of deep learning in flue pipe type recognition. The main thesis is the possibility of recognizing the type of labium based on the sound generated by the flue pipe. For the purpose of our work, we prepared a large data set of high-quality recordings, carried out in an organbuilder’s workshop. Very high accuracy has been achieved in our experiments on these data using Artificial Neural Networks (ANN), trained to recognize the details of the pipe mouth construction. The organbuilders claim that they can distinguish the pipe mouth type only by hearing it, and this is why we decided to verify if it is possible to train ANN to recognize the details of the organ pipe, as this confirms a possibility that a human sense of hearing may be trained as well. In the future, the usage of deep learning in the recognition of pipe sound parameters may be used in the voicing of the pipe organ and the selection of appropriate parameters of pipes to obtain the desired timbre.
Article
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Time frequency analysis of sounds produced during the initial transients of flute like instruments, (recorders and organ pipes) show that the build-up of the different harmonics of the steady state sounds is preceded by a group of acoustical phenomena - noises, inharmonic tones - which are very important for the perceived quality of the transients. In this paper, initial transients produced by a complete flue pipe instrument (mouth tones) are compared with those produced by the same mouthpiece disconnected from the pipe (edge tones) on several instruments: organ pipes and recorders. Mouth tones from the initial transients of a complete instrument are, just like edge tones, mainly controlled by the mouth parameters: speed of jet at flue exit; and distance between flue exit and labium; they therefore correspond to self-oscillation of the mouth. During pressure build-up and when frequencies coincide, mouth tones can stabilise on one resonant mode of the pipe, creating an inharmonic forerunner which has been observed by many authors. In general, mouth tones, which are due to "mouth behaviour" of the jet, disappear as soon as the regular steady state is established. However, a paradoxical functioning where mouth tones and harmonics of the first mode are coexisting is sought for when voicing a specific organ stop: the viola 4' of the Italian organ. The musical relevance of mouth tones is discussed for the recorder as well as when voicing specific organ stops.
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Attack transients in organ pipes are investigated by analyzing slow-motion pictures from the smoked-jet visualization with a high-speed digital video camera. In our experiment the attack is very slow and the 90% rise time of the blowing pressure is over 50 fundamental periods. Also, lower final blowing pressures (typically 150Pa) and longer cutup lengths (10.2 and 15.8 mm) are used. Although the jet issuing from the flue almost always deviates exteriorly, the jet impinging straight on the edge is incidentally observed. This head-on impinging jet is followed by two symmetrical forward-spinning vortices. The exteriorly-deviating jet is characterized by the type of the vortex formed during initial jet-edge interaction: (1) no vortex; (2) a forwardspinning vortex just beneath the edge; (3) an almost stationary vortex before the edge; (4) a backspinning vortex just beneath the edge (this example is borrowed from M. P. Verge et al. [1], and is observed when a very fast attack is applied to a short pipe with a short cutup). A forwardspinning vortex seems to promote a smoother buildup of the jet wave; a backspinning vortex yields complicated interactions among the main jet flow, its side flow, the entrained flow, and the edge; a stationary vortex largely retards the jet-wave buildup by inducing the two-crest (hydrodynamically second) mode; two symmetrical vortices need reaction time to adapt themselves to asymmetrical sinuous disturbance along the jet. Also, a kind of subharmonic jet oscillation occurs during this transformation. The two-crest mode is followed by complicated transfigurations such as the three-crest mode before the ordinal one-crest mode is established. The presteady state just prior to the steady state is characterized by the acoustic vortex shedding from the edge surface, which however disappears at the steady state.
Article
Full-text available
Time frequency analysis of sounds produced during the initial transients of flute like instruments, (recorders and organ pipes) show that the build-up of the different harmonics of the steady state sounds is preceded by a group of acoustical phenomena - noises, inharmonic tones - which are very important for the perceived quality of the transients. In this paper, initial transients produced by a complete flue pipe instrument (mouth tones) are compared with those produced by the same mouthpiece disconnected from the pipe (edge tones) on several instruments: organ pipes and recorders. Mouth tones from the initial transients of a complete instrument are, just like edge tones, mainly controlled by the mouth parameters: speed of jet at flue exit; and distance between flue exit and labium; they therefore correspond to self-oscillation of the mouth. During pressure build-up and when frequencies coincide, mouth tones can stabilise on one resonant mode of the pipe, creating an inharmonic forerunner which has been observed by many authors. In general, mouth tones, which are due to "mouth behaviour" of the jet, disappear as soon as the regular steady state is established. However, a paradoxical functioning where mouth tones and harmonics of the first mode are coexisting is sought for when voicing a specific organ stop: the viola 4' of the Italian organ. The musical relevance of mouth tones is discussed for the recorder as well as when voicing specific organ stops.
Article
Application of the ears to the flue organ pipe is one of the important voicing techniques. Ears are the projections on both sides of the pipe mouth. Organ builders say the ears make not only the sound lower and darker, but also the buildup of tone smoother and quicker. The aim of this research is to confirm their recognitions and make the causes clear. For that purpose, we made acoustical and flow measurements (measurement of the velocity profiles at the mouth) with model pipes. As a result, we could confirm the recognition of the organ builders. In addition, our experiments indicate a slight increase in the blowing pressure in the foot and an increase in the inharmonicity of the pipe eigenmodes. The ear reduces the maximum jet velocity but keeps the characteristic profiles. In some cases, the profiles move as a whole more inside of the pipe. Recent acoustic measurements (eigenmodes of the pipe resonator and of the mouth tone, attack transient and stationary spectrum) on real organ pipes with ears of different heights will be also reported at the meeting.
Article
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Article
A wind supply with adjustable pressure rise time is used to study the initial transients of adjustable stopped and open flue pipes which approximate classic voicing. The precursor, at several times the fundamental frequency, and a subsequent oscillation dominated by the next mode above the fundamental, are strongest when the pressure rise time is somewhere between 1 and 10 fundamental periods. These features may vanish for much longer or shorter rise times. Decreasing the inharmonicity of the resonances increases the next-mode content in the attack, as does reducing the cutup. External sound at the fundamental frequency, applied either at the pipe mouth or through the air supply, suppresses both the precursor and the subsequent next-mode burst. The precursor does not involve a longitudinal pipe resonance. Pipe frequencies were 198-256 Hz. Air supply pressure was 530 Pa. A computer simulation, based on an oscillator model with three resonant modes and time-delayed nonlinear feedback, incorporating ideas of N. H. Fletcher and others, accounts for major features of the experimental results. The suppression of the initial next-mode burst when the pressure rises slowly is caused by the extra time spent in a pressure range where the feedback loop gain (particularly the phase) for the next mode does not support self- oscillation. With sufficiently fast pressure rise, impulsive excitation favoring the fundamental enables it to dominate the attack, preventing the next-mode burst.
Article
This article is an over view of the characteristic sound properties of flue organ pipes. The characteristic properties of the stationary spectrum and attack transient have been surveyed and assigned to properties of the physical systems (air column as acoustic resonator, air jet as hydrodynamic oscillator and pipe wall as mechanical resonator) involved in the sound generation process. The measurements presented underline the primary role of the acoustic resonator in the stationary sound and of the edge tone in the attack.
Article
andreas.bamberger@physik.uni-freiburg.de The PIV (Particle Image Velocimetry) is a useful measurement tool to investigate the field of fluid and/or acoustic flows in semi-quantitative manner. The particles for flow visualization are instantaneously captured by the laser sheet with very high resolution. Two separate particle images taken with an interval of ten-microsec order are statistically analysed and then the velocity map is derived. This paper reports the results of PIV application to three different cases. (1) Application to the flute evaluation: A metal flute for students and a newly-designed ceramic flute for advanced players are mechanically blown using a common headjoint. The laser sheet illuminates the embouchure vertically and the resulting cross section is viewed through a window made by cutting the headjoint at the cork position. The flow field inside the flute, particularly the vorticity distribution can reflect the difference in flute quality. (2) Application to functional characterization of the organ-pipe ears: The ears are the projections on both sides of the pipe mouth and provide an important voicing technique. Flow measurement around the mouth and the resulting jet movement demonstrate the effectiveness of the ears. (3) Applications to the vortex-sound theory on organ pipes: Focusing on a closer vicinity of the jet flow, velocity vectors crossing the jet are detected and they seem to interact with a strong vorticity formed near the crossing region. Such a configuration may be relevant to the mechanism of vortex-sound generation in organ flue pipes.
Using piecewise-periodic techniques, the attack transients of almost 200 different organ pipes from 33 ranks have been analyzed. Results for 44 pipes representing 10 ranks are discussed in detail in this paper. In addition to the steady-state parameters of frequency and amplitude, transient duration, overshoot, delay and stability are used to describe the attack transients, and it is shown how each pipe, rank, and family differs from the others in these respects. Norms for the four families, flutes, foundations, strings, and reeds, are proposed. Recognizing the importance of attack transients in characterizing musical sounds, these results provide a unique aid in the design of instruments, traditional or electronic, that generate pipe organ sounds. The technique of piecewise-periodic analysis can, in addition, be used on many other musical instruments and synthesizers as an aid in their design, manufacture, and operation.