Ranks Of Pipes Research Articles

Time domain simulations of a novel lingual organ pipe construction

In a traditional pipe organ, the dynamic range of both labial (flue) and lingual (reed) pipe ranks are strictly limited as each rank is tuned and voiced to a nominal windchest pressure. Changing this pressure not only affects the amplitude of the radiated sound but both the pitch and the timbre of the pipes. A new pipe construction with a blown open free tongue was proposed recently to overcome this limitation. Prototype pipes of the new construction were built and measurements were carried out on them at different blowing pressures. It was found that the new construction provides a pleasing stability of the pitch and a broad range of playable amplitudes; however, the timbre of the pipes changes significantly with the blowing pressure. To improve the design in the latter aspect, a physical model of the pipes needs to be established first. In this contribution the sound generation of the experimental pipes is simulated by time domain computations. The resonator and its interaction with the vibration of the tongue are simulated using both the truncated impedance model and the reflection function approach. Results of the temporal simulations and their comparison with measurements are presented.

Roughness of organ pipe sound due to frequency comb

In the sound spectrum of flue organ pipes in addition to the usual harmonic partials, sometimes a series of equidistant but not harmonic lines can be found. This phenomenon has been observed in the recorded sound of pipes from different pipe ranks. The second set of spectral lines is similar to "frequency combs" used in optics for accurate measurement of optical frequencies. Analysis of measured sound spectra with and without frequency comb and simulations are presented and discussed in the paper. The appearance of frequency combs in the sound spectrum is explained by a model that assumes the presence of a mouth tone in addition to the pipe sound. Mouth tone bursts are generated when the oscillating air jet passes the upper lip. The burst repetition frequency is locked to the fundamental frequency of the pipe and the bursts are coherent with a pulse-to-pulse phase shift. The phase shift explains the observed frequency offset of the frequency comb to the harmonic frequencies. The simulations also show that weak and fluctuating mouth tones cannot generate frequency comb due to a lack of coherence.

The influence of reed curvature on the tone quality of lingual organ pipes.

Given certain design constraints, such as the type of stop being voiced and the desired tone quality, reed voicers must use consummate skill to curve each tongue so as to produce the best and most stable tone, as well as maintain a consistent tone quality across an entire rank of pipes. The curvature given to a reed tongue influences not only the harmonic structure of the steady-state sound, but also the attack. Two fundamentally different types of curvature are typically employed, the chorus reed (trompette) curve (which yields a bright sound) and the smooth-toned curve employed for solo reeds such as the clarinet. This study investigated the effect of reed curvature on the vibration and tone of reed tongues of both types. Two F2 pipes (a trompette and a clarinet) were constructed and voiced with six different tongues each to produce a variety of tones. The reed’s vibration was measured under typical conditions by laser vibrometer; the pressure waves in the boot and in the shallot were measured by means of 1/8-in. microphones and the emitted sound was recorded at the egress. By performing various measurements simultaneously, phase differences were also determined.

The influence of curvature on the vibration and tone quality of pipe organ reed tongues.

Given certain design constraints, such as the type of stop being voiced and the desired tone quality, organ reed voicers must curve each tongue so as to produce the best and most stable tone, as well as maintaining a consistent tone quality across an entire rank of pipes. This study investigated the effects of varying tongue curvatures on two pipes, an F2 Trompette and an F2 Clarinet. Reed vibration was measured under typical conditions by laser vibrometer; the pressure waves in the boot and shallot were measured by means of one-eighth inch microphones and the emitted sound was recorded at the egress. By integrating the velocity data, the displacement of the reed may be plotted in tandem with the pressure difference across the reed, allowing tongue position to be plotted versus the pressure variation during one steady-state cycle for each reed while vibrating. These graphs can then be compared and correlated to the observed tone quality for each of the differently curved reeds.

Influence of the edge tone (mouth tone) on the sound of flue organ pipes as a function of pipe scaling

The sound quality of an organ pipe is mainly influenced by the attack transients. This onset is first dominated by the edge tone, while later the pipe resonator will play a more important role. To understand the physics of a flue organ pipe, it is necessary to analyse the edge tone, the acoustic properties of the pipe resonator, the attack transient and the stationary sound of the pipe. Several pipe ranks have been investigated in the anechoic room of the Fraunhofer IBP: Nachthorn, Diapason, Gamba, Octave, Flute, Geigenprinzipal, Salizional. By the evaluation all physical effects contributing to the production of sound were taken into account. In the present paper about the physical effect of the edge tone on the production of the pipe sound will be reported.

Cathedral acoustics and organ sound reinforcement

The acoustic characteristics of 4 UK cathedrals have been investigated. In three of the buildings it is reported that the organ requires additional support or reinforcement to cope with the large volume of the space involved. All 4 buildings were found to exhibit multiple coupled spaces making it difficult to accurately assess the active acoustic volume. In order help to overcome the perceived lack of ’volume’ from the organ, in two of the cathedrals, it is proposed to install a second rank of pipes some distance down the nave from the main organ. The acoustic and psychoacoustic implications if this approach are discussed. An alternative means of providing support for the organ via the installed sound reinforcement system has also been investigated and the electroacoustic and subjective requirements for this are discussed and reviewed.

Onset transient significance in listener identification of pipe organ stops

Pipe organs typically contain many ranks of pipes, but it is uncertain whether listeners can discern the often subtle differences between different ranks. The importance of onset transients in timbral identification is well established, but in many pipe organ listening situations, the transient is obscured. This paper explores the significance of organ pipe onset transients in an experiment based on Berger’s work on orchestral timbre (K. W. Berger, J. Acoust. Soc. Am. 36, part II, 1888 (1963)] Listeners familiar with the pipe organ attempted to identify recordings of single organ pipes, representing commonly found types of organ stop. Each pipe was presented on different occasions with its own transient and with artificial transients created by amplitude ramps. The results demonstrate that when onset transients are present, expert listeners are adept at identifying the general tonal nature of a stop, but are less adept at precise identification. Replacement of transients with amplitude ramps resulted in a decrease in both precise and general correct identification. The subjective mapping demonstrated between pipe names and their spectral features is explored. Onset transients are shown to be important in listener identification of pipe organ stops.

The influence of reed curvature on the tone quality of lingual organ pipes

Given certain design constraints, such as the type of stop being voiced and the desired tone quality, reed voicers must use consummate skill to curve each tongue so as to produce the best and most stable tone, as well as maintaining a consistent tone quality across an entire rank of pipes. The curvature given to a reed tongue influences not only the harmonic structure of the steady‐state sound, but also the attack. Two fundamentally different types of curvature are typically employed, the chorus reed (trompette) curve (which yields a bright sound) and the smooth‐toned curve employed for solo reeds such as the clarinet. This study investigated the effect of reed curvature on the vibration and tone of reed tongues of both types. Two F2 pipes (a trompette and a clarinet) were constructed and voiced with 6 different tongues each to produce a variety of tones. The reed’s vibration was measured under typical conditions by laser vibrometer; the pressure waves in the boot and in the shallot were measured by means of one‐eighth inch microphones and the emitted sound was recorded at the egress. By performing various measurements simultaneously, phase differences were also determined.

Nicholas Thistlethwaite and Geoffrey Webber, eds. The Cambridge Companion to the Organ. Cambridge Companions to Music. Cambridge: Cambridge University Press, 1998. xiv, 340 pp. ISBN 0-521-57309-2 (hardcover), 0-521-57584-2 (paperback)

Nicholas Thistlethwaite and Geoffrey Webber, eds. The Cambridge Companion to the Organ. Cambridge Companions to Music. Cambridge: Cambridge University Press, 1998. xiv, 340 pp. ISBN 0-521-57309-2 (hardcover), 0-521-57584-2 (paperback). Un article de la revue Canadian University Music Review / Revue de musique des universités canadiennes (Volume 20, numéro 2, 2000, p. 1-155) diffusée par la plateforme Érudit.

Tonal portrait of a pipe organ

Measurement techniques are described that enable the steady state tone color (timbre) of a musical instrument to be quantified. The system is applied to sounds from the pipe organ in the Great Hall of Sydney University. A one-third octave normalized loudness spectrum that is independent of pitch is derived for each set of notes from selected ranks of pipes. From the normalized spectrum, sharpness and tristimulus coordinates are computed, the latter being independent of both pitch and loudness. Measurements made on different ranks of pipes or made at different times are compared with the aid of spectrum dissimilarity and tristimulus diagrams.

Documentation of the sound of a historical pipe organ

The problem of documenting and archiving the characteristic tone quality of the different pipe ranks of a historical organ is discussed. While the musical quality of a certain instrument may be represented by recording organ concerts, the characteristic timbre of the pipe ranks can be investigated by measuring and storing the spectra and attacks of the individual pipes belonging to the rank. The effect of room resonances on the pipe tones are also investigated. Finally, the experiences collected by the preparation of the first tone documentation in Naumburg are revised.

Effect upon intensity and low frequencies due to a sound moat in the new Chapel/Recital Hall at the Interlochen Center for the Arts

Graphic results of a study of the application of music‐acoustical principles in the low frequencies of pipe ranks in the Aeolian‐Skinner Organ of the new Dendrinos Chapel/Recital Hall of the Interlochen Center for the Arts. The effect upon pitch and timbre as well as the intensity and frequency resulting from the sound moat under the stage of the new structure reveals a reassessment of physical features and psychological responses in musical understanding. However the direct acoustical estimations and provisions agree with earlier assumptions, especially J. F. Schouten's “subjective tones.”

Scaling rules for organ flue pipe ranks and for the string choirs of harpsichords

The criteria for design of an organ flue pipe rank, properly balanced and coherent in power and harmonic development, are discussed in terms of present understanding of the sound production process. A scaling with pipe diameter D proportional to ν1−x, where ν1 is pipe fundamental frequency and x = 0.83, is found to give approximately constant harmonic development across the rank but too much loudness in the bass. The traditional scaling rule with x = 0.75 nearly equalizes the loudness and increases harmonic development towards the bass of the rank. Similar criteria applied to the string choirs of harpsichords, in which decay time must be considered as well, lead to scaling rules which increase wire diameter and move the plucking point progressively towards the end of the string in the bass. The relations between the two types of scaling rule are discussed.

External Surface-Absorption Cross Section of a Pipe Organ

The total sound absorption due to a rank of organ pipes arises chiefly from internal resonance losses and also from energy dissipation taking place at the external surfaces of the pipes. The first contribution has been discussed elsewhere [A. H. Benade, J. Acoust. Soc. Am. 38, 780–789 (1965)], and the second is reported here. Scattering of a plane wave incident obliquely on a long circular cylinder is calculated, and the results are used to find the energy absorbed via viscosity and also via the short-circuiting of the wave's temperature fluctuations produced by an isothermal boundary. It is shown that an absorption coefficient can be defined for the pipe surface that is approximately independent of the radius/wavelength ratio. The corresponding coefficient for viscous and thermal losses at a plane surface is also calculated. The result are ᾱcyl = 2.3⋅10−5(ω)12 and ᾱPLANE = 6.8⋅10−5(ω)12. The latter result agrees with a calculation by Walther [J. Acoust. Soc. Am. 33, 127–136 (1961)]. Computation of the absorption by a rank of pipes is simplified by using the scaling principles followed by organ builders. It is shown that the external absorption is negligible below 500 Hz, and is only about 0.06 m2 at 2000 Hz for a 73-pipe rank centered at middle C.

Resonance-Absorption Cross Section of a Pipe Organ

Each chromatic rank of pipes in gu organ provides a set of resonant absorbers for reverberant sound. The averaged internal absorption of pipes resonating near angular frequency ω is ρ̄ = (2π2/0.06) (c2/ω3) (Γr/Γ) (Γ − Γr). The resonance width Γ is the sum of the widths Γr, Γw, Γm, arising from radiation, wall losses, and viscosity in the mouth region. The velocity of sound is c. Organ pipes (radius a and length L) are scaled so that a∼Lβ, so that absorption by a pipe that resonates at ω in its nth mode is expressible via the properties of a pipe whose fundamental is ω, with radius a, radiating area S, and mouth end correction E. Many pipes in rank absorb strongly at any given frequency. The major contribution comes from the largest pipes excited in their higher modes. A 73-pipe rank centered at middle C can give a total resonance absorption as high as 0.5 m2 at 62 cps, down to about 0.028 m2 at 2000 cps. Absorption by external pipe surfaces (calculated elsewhere) is negligible, except at the highest frequencies.

Absorption Cross Section of a Pipe Organ

Each chromatic rank of pipes in an organ provides a set of resonant absorbers for reverberant sound. The average absorption of a pipe near resonance is σ̄=(2π2/.06) (c2/ω3) × (Γr/Γ) (Γw+Γm). The resonance width Γ is the sum of the widths Γr, Γw, Γm, arising from radiation, wall losses, and viscosity in the mouth region. If the pipes are scaled so that α∼lβ, much computation is saved, since absorption by the pipe that resonates on its nth harmonic is expressible via the properties of the pipe whose fundamental is ω, and having radius a, radiating area S, and month end correction E. Thus, an open pipe near its nth harmonic has Γr=(S/2πlc) n2β−1ω2, and Γw=(2Ac/anβ) (ω)12. For metal pipes, Γm ≅ (4c/π) (2μ/ω)12(1/α)2(1/n)2β+1/[1+(ωEnβ/c)2]. Losses are somewhat changed by resonances in the pipe foot. The net absorption of an organ can alter the room reverberation time appreciably.

Electronic Production of Choral Tone

An important quality of traditional musical sound is the rich ensemble effect which results in part from the combination of multiple sources that have the same nominal pitch but slightly different frequencies. Organ builders provide celeste ranks of pipes which are intentionally detuned from their neighbors. Electronic organs generally have fewer sources than pipe organs at a given pitch and their oscillators are inherently much more stable in frequency. It is not necessary to provide an extra set of detuned electrical generators for it is possible to translate signal frequencies electronically. This is accomplished by a group of single-side band, suppressed carrier modulators, and associated band-pass filters. The combined modulator outputs are preferably acoustically radiated by a loudspeaker channel which is spatially separated from the unmodulated loudspeaker channel in order that a subjective dimensional impression be achieved. Equipment of this type can be added to any electronic music system to provide a new set of sources of similar timbre yet transposed in frequency either up or down from the corresponding input frequencies. From an economic standpoint, the musician is thereby provided with many more sources for only a modest increment in cost.

Acoustical Design of Modern German Organs

Previous work on the acoustical qualities of several famous baroque organs, which is here reviewed, reveals two maxima in the spectra of the “plenum” sounds, one at lower frequency formed by the fundamentals and lower harmonics, and one at a higher frequency formed by the partial tones of the mixture stops having several ranks of pipes. In Germany where many organs were destroyed in the last war, organists and parishes want to get new instruments of the same or a similar sound quality as the famous baroque organs. If approached in the usual way, this goal is reached only by extraordinary effort and dexterity. It is possible by acoustical planning, however, to attain with accuracy the desired spectra in a relatively short time. Two characteristic examples of such research are described here: the Praetorius organ at Freiburg and the Choir organ of St. Mary's Cathedral at Lübeck. In the first case, room acoustics were planned to get the desired sound-energy distribution for the organ. In the second case, proposals for the diameters and the installation of the pipes were made to adapt the organ to the room acoustics, in order to reproduce the characteristic baroque sound spectra in the nave of the church.

Mistuning Desirable in Organs, Pianos, Choruses, and Orchestras

See paper D1, American Physical Society meeting, June 26, 1951. Tone quality of a chord depends on more than the strength of harmonics. Organ builders have for years included “celeste” stops amongst the softer stops. They consist of two or more ranks of pipes, mistuned about 0.1 semitone (approximate pitch threshold of ear) to produce beats which increase in frequency with pitch; when a chord is played there is a scintillation of tone which is more subtle than the tremulo in which all tones vary in volume synchronously. A pipe organ played at full volume needs no intentional mistuning as there are then many pipes speaking one pitch and it is impossible to have all pipes for a given pitch, tuned perfectly to each other. Electric organ companies have failed to realize the importance of “celeste” or “chorus” stops—two use them but only in a limited way. The same effect is observed if the three strings of a piano note are not too well-tuned. A chorus sounds better than a quartet and a full string orchestra sounds better than a string quartet for the same reason—no two violinists (or singers) can possibly play (or sing) exactly the same pitch.

Vox Angelica

MANY of your readers may be acquainted with the nature of the Vox Angelica stop on a good organ. It consists of two ranks of pipes of small scale and delicate quality of tone, one of which is tuned slightly sharp, so that a wavy (hence called Unda Maris) sound is produced. Now it is possible to obtain very similar effects on an ordinary Estey American organ. Given the viola and violetta stops to be drawn out, wrap a band of india-rubber (an ordinary elastic band does very well) round the neck of the viola stop so that it cannot return completely home, on moderate pressure, and allowing a fraction of an inch to intervene between its true final position when inactive; beats will be heard of intensity depending upon the deviation from complete occlusion of this stop. The nearer the viola stop is to occlusion the more rapid the beats; but it is undesirable to obtain rapidity, as the lower notes are too prominently out of tune in this case. Any body can, by experiment, determine the proper amount of deviation to be employed, and having done this the effect is remark ably good. On an Estey, the two stops mentioned are the only admissible ones for such an experiment, from consideration of overtones. No doubt some of your readers may adopt a more elaborate and convenient method of regulating the deviation than by elastic bands, after some experiments. It may seem a paradox to obtain beautiful concordant effects by the use of discordant vibrational relations, but it is undeniable that on a first-class organ the Voix Celeste, or Vox Angelica, or Unda Maris, is a most beautiful stop, and is capable of producing perfect con sordini effects.