Tenor Steelpan Research Articles

Characterizing the vibrational behavior of steelpans with a reduced number of notes

The skilled artisans who construct lead (tenor) steelpans generally attempt to tune the first three resonances of each note harmonically. When successful, the tuning leads to neighboring notes sharing the same frequency for the first two harmonics of each note on the outer ring of the steelpan. The sympathetic excitation of the neighboring notes is believed to contribute significantly to the unique timbre of the steelpan's characteristic sound. A series of custom steelpans with fewer notes was commissioned to understand better the nature of the coupling between the struck note and sympathetically vibrating notes. Electronic speckle pattern interferometry was used to compare the coupling between notes on standard tenor steelpan with the coupling between notes on the customized steelpan having fewer notes.

Using convolutional neural networks to estimate pitch directly from steelpan audio signals

Estimating the pitch, or fundamental frequency, of a monophonic audio signal is a fundamental task in computational audio analysis with many downstream applications such as automatic transcription. The current general state of the art method for pitch detection is CRéPE: a Convolutional Representation for Pitch Estimation. CRéPE is a deep convolutional neural network designed to estimate the fundamental frequency of an audio signal directly from the waveform. However, CRéPE, and other general pitch detection methods, do not perform well on steelpan audio. This is likely due to the steelpan's complex spectral characteristics that differentiate it timbrally from other sound sources. We combine a deep convolutional neural network architecture based on CRéPE with a training dataset of steelpan audio from several distinct sounding tenor steelpans to achieve improved tenor steelpan pitch detection directly from the audio signal. We assess our model's ability to generalize by evaluating it with a test dataset that includes audio samples from steelpans that have no samples as part of the training set and compare these results to CRéPE's performance on the same test dataset.

Improved steelpan pitch detection through audio feature extraction and machine learning

The steelpan, a significant musical instrument invented in the mid-20th century, is a harmonically complex system making fundamental pitch detection a difficult task. Initial experiments using state-of-the-art pitch detection algorithms have shown significant difficulties in detecting the pitch of individual steelpan notes. This paper presents a method of improved pitch detection accuracy by combining music information retrieval techniques with machine learning algorithms. An audio sample set consisting of thousands of steelpan notes from ten different tenor steelpans is used to quantitatively evaluate the proposed methodology. Low-level audio features are extracted from the audio samples and used to train a machine learning algorithm which identifies the salient features for pitch estimation. This method’s performance is measured against the current state-of-the-art pitch detection methods, pYIN (a probabilistic autocorrelation method) and CRéPE (a convolutional neural network-based method), showing improved performance at steelpan pitch detection. The machine learning model developed for this paper using this methodology is focused on the tenor steelpan but is intended to lead to a more generalized model for pitch detection of all types of steelpans.

Searching for early reflected waves after strike of Caribbean steelpan using time-resolved electronic speckle pattern interferometry

Electronic speckle-pattern interferometry has become a popular tool for studying the operating deflection shapes and normal modes of musical instruments. Normally, ESPI is used with cameras having frame rates below 50 Hz, and the resulting interferograms are the result of a time average over many oscillations. Using ESPI with a high speed camera operating at frame rates of several thousand frames per second allows for time-resolved examinations of transient motion, and this technique has been used to study the motion immediately following the strike on a Caribbean steelpan. Caribbean steelpans are a complex system of coupled oscillators and it has been suggested that the inflections from the concave shape of the steelpan bowl to the convex shape of the note areas serves as a boundary where mechanical waves are partially reflected. High speed ESPI movies of strikes on a low tenor steelpan were acquired in an effort to search for evidence of these reflected waves.

A method for predicting the performance of a steelband orchestra in arbitrary environments

One of the challenges in steelpan performance is in determining the best placement of the various instruments in an orchestra so as to achieve the level performance desired by the musical arranger. This research attempts to develop a method for analyzing the performance of the tenor steelpan in arbitrary acoustic spaces using the room acoustic modeling software, Enhanced Acoustic Simulation for Engineers (EASE). When provided with an acoustic characterization of a speaker system, particularly the magnitude and phase radiation data, and the room in which it is located, EASE can be used to predict the resulting acoustic sound-field. EASE also requires an electrical equivalent of the instrument's sound source and, through its auralization feature, allow the user to actually hear an actual performance. EASE uses a variety of reconstruction techniques, such as ray tracing and boundary element method, to provide the most accurate responses. The study will verify the approach by comparing simulation results on direct sound coverage, total SPL, Clarity (C80), Centre Time, Reverberation, and Early decay times of the instrument with real time measurements in the usual 1/3-band octave frequency resolution. Although the work focuses on the tenor steelpan, it can be easily extended to predict the performance of an entire ensemble of steelpans in any given space.

Characterization of the mechanical properties of the steelpan

The steelpan is a struck idiophone whose playing surface is constructed by forming the top of a fifty-five gallon steel oil drum into a sunken, nearly hemispherical surface and then raising smaller shells on the hemisphere to form notes. The completed instrument resembles an inverted turtle shell and is played by striking the notes with sticks. Although it is understood that variations in note geometry and material properties are mainly responsible for the characteristic sounds generated when the notes are struck, few studies have investigated these relationships. Previous research efforts have explored the metallurgical properties and the characteristic vibrations of the notes. Less emphasis has been placed on the relationship between the mechanical properties of the steelpan and its acoustic behavior. In this research, the variation in the mechanical properties across the playing surface of a tenor steelpan is characterized. Of the instruments in the steelpan family, this instrument has the greatest deformation and the most notes. More specifically, the variation in the residual stress, strength, Young’s Modulus, and Poisson’s ratio are determined and compared among octave sets. This characterization is important for the development of models that relate the mechanical properties to the acoustical behavior of the steelpan.

Conformal scanning laser Doppler vibrometer measurement of tenor steelpan response to impulse excitation

A conformal scanning laser Doppler vibrometer system is used in conjunction with a mechanical pannist to measure the surface normal vibration of the entire playing surface of a C-lead tenor steelpan. The mechanical pannist is a device designed to deliver controlled, repeatable strikes that mimic a mallet during authentic use. A description of the measurement system is followed by select examples of behavior common to the results from three different excitation notes. A summary of observed response shapes and associated frequencies demonstrates the concerted placement of note overtones by the craftsmen who manufacture and tune the instruments. The measurements provide a rich mechanical snapshot of the complex motion that generates the distinctive sound of a steelpan.

Sound radiation from Caribbean steelpans using nearfield acoustical holography

The sound-field of a Caribbean low tenor steelpan is examined using nearfield acoustical holography (NAH). The particular instrument, a Bertrand Kelman low tenor, has been previously examined in a single plane using a four microphone sound intensity technique. This paper will examine the sound radiation in a cuboid space enclosing the instrument at three frequencies. Presented will be the results of sound pressure level (SPL), active acoustic intensity (AI), and reactive acoustic intensity (RI) obtained through application of the NAH technique. The limitations of NAH when applied to an irregularly shaped object such as a tenor steelpan will also be presented.

Novel exploration of the vibration of the Caribbean steelpan in response to authentic excitation.

A novel conformal scanning laser vibrometer was used to determine the vibrational modes of a C-lead tenor steelpan. The measurements provide a rich mechanical snapshot of the artistry involved in the marriage of metallurgy and music theory that goes into the creation of the instrument. The data represent the surface-normal motion of the entire face of the instrument in response to an impulsive excitation intended to mimic the strike of a mallet. A traditional scanning laser Doppler vibrometer is limited to measurement of planar geometries and therefore is of limited utility on the highly contoured surface of the steelpan. A description of the novel measurement system is presented, followed by the surface velocity data and a summary of response shapes and the frequencies at which those responses occur. The data show that individual note areas respond when adjacent or non-adjacent musically related notes are struck and clearly illustrate the complex vibration of the steelpan and the coupling between notes that produce the rich distinctive nature of the steelpan sound.

Phase mapping and sound radiation from Caribbean steelpans

The Caribbean steelpan is one of the most interesting acoustic musical instruments invented in the last century. Although simple in design, the acoustic properties of the steelpan are surprisingly complicated. Holographic interferometry was used to determine the resonances of a low tenor steelpan. Placement of a vibrating mirror in the optical path of the reference beam expands the capabilities of the holography system to include phase measurements. Phase maps of several low resonances of notes on a Caribbean steelpan will be shown. Sound intensity measurements were taken to explore the relationship between the resonances and the radiated sound field. The pan was placed in an anechoic chamber, and selected notes were excited electromagnetically with a swept sinusoid signal. A two-microphone probe was used to gather sound intensity measurements. Sound intensity maps of the first three harmonics will be shown for several notes.

Sound radiation from Caribbean steelpans

Besides radiating sound from the note area being struck, a steelpan radiates from neighboring note areas that vibrate sympathetically, from the areas between notes, and from the skirt [Rossing et al., Phys. Today 49(3), 24-29 (1996)]. Measurements were taken in an anechoic chamber using a four-microphone intensity probe to visualize the acoustic radiation from selected notes on a double second and a low tenor steelpan. Swept sinusoidal excitation was effected using an electromagnet. Sound intensity maps were drawn for the first three harmonics.

Modal analysis and sound radiation from Caribbean steelpans

The Caribbean steelpan is one of the most interesting acoustic musical instruments invented in the last century. Although simple in design, the acoustic properties of the steelpan are surprisingly complicated. Holographic interferometry was used to determine the modes of vibration of a double second and a low tenor steelpan. Sound intensity measurements were taken to explore the relationship between the modes of vibration and the radiated sound field. The pan was placed in an anechoic chamber, and selected notes were excited electromagnetically with a swept sinusoid signal. A two-microphone probe was used to gather sound intensity measurements. Sound intensity maps and animations were constructed for the first three harmonics.

Measuring residual stresses in a steelpan

By bonding strain gage rosettes to a steelpan and drilling a small hole, it is possible to measure the residual stresses at selected locations on a steelpan. The accuracy of the method depends upon the extent to which the stresses and strains change with depth below the surface on which the strains are measured. The residual stresses in a tenor steelpan, ‘‘sunk’’ by hammering in the usual way, appear to be mostly compressive in the middle ring of notes, changing to tensile in the outer ring. The effect of heating on the residual stresses is discussed.

Modal analysis of a new steelpan: The ping

The ping, which has the same playing range as a tenor steelpan, is a new instrument in the steelpan family. Its playing surface is sandwich hardened steel having a uniform thickness of 0.9 mm, and its skirt is of stainless steel 1.25-mm thick. Each note area has a small elliptical dome at the center to provide stability and a durable strike point. We compare the modes of vibration of the ping to those of a tenor steelpan. In both pans, the (0,1) mode of each note is tuned an octave above the fundamental, and the (1,0) mode is tuned a twelfth (three times the frequency) above the fundamental in the lower notes. In the ping, it is possible to tune a twelfth throughout more of the range, and the frequency remains unchanged for a longer time during hard playing. Radiation of sound by the skirt is compared.

Vibrational modes of a tenor steel pan

The tenor or lead pan has 28 or 29 notes covering the range of C4 to E6. In spite of its being the lead voice in a typical steel band, little research has been reported previously on its modes of vibration or its acoustical behavior. Using electronic TV holography, we have studied the modes of vibration of the various note areas in tenor pans by two different makers. Note areas generally have one or two overtone modes tuned harmonically to the fundamental [Rossing et al., Phys. Today 49(3), 24–29 (1996)]. Special attention has been paid to the strong acoustical and mechanical coupling between the note areas as they vibrate.