Search

We train an object detector built from convolutional neural networks to count interference fringes in elliptical antinode regions in frames of high-speed video recordings of transient oscillations in Caribbean steelpan drums, illuminated by electronic speckle pattern interferometry (ESPI). The annotations provided by our model aim to contribute to the understanding of time-dependent behavior in such drums by tracking the development of sympathetic vibration modes. The system is trained on a dataset of crowdsourced human-annotated images obtained from the Zooniverse Steelpan Vibrations Project. Due to the small number of human-annotated images and the ambiguity of the annotation task, we also evaluate the model on a large corpus of synthetic images whereby the properties have been matched to the real images by style transfer using a Generative Adversarial Network. Applying the model to thousands of unlabeled video frames, we measure oscillations consistent with audio recordings of these drum strikes. One unanticipated result is that sympathetic oscillations of higher-octave notes significantly precede the rise in sound intensity of the corresponding second harmonic tones; the mechanism responsible for this remains unidentified. This paper primarily concerns the development of the predictive model; further exploration of the steelpan images and deeper physical insights await its further application.

The synthesis of convincing acoustic drum sounds remains an open problem. In this paper, a method for analysing and synthesising pitch glide in drums is proposed, whereby the discrete cosine transform (DCT) of an unwindowed drum sound is modelled. This is an extension of the scheme initially proposed by Kirby and Sandler [(2020). Proceedings of the 23rd International Conference on Digital Audio Effects, Vienna, Austria, pp. 155-162], which was able to reproduce key components of drum sounds accurately enough that they could not be distinguished from the reference samples. Here, drum modes were analysed in greater detail for a tom-tom struck at 67 different intensities to investigate their evolution with strike velocity. A clear evolution was observed in the DCT features, and interpolation was used to synthesise the modes of intermediate velocity. These synthesised modes were evaluated objectively through null testing, which showed that a continuous blending of strike velocities could be achieved throughout the data set. An AB listening test was also performed, where 20 participants attempted to distinguish between pairs of real and synthesised sounds. Exactly 50% accuracy was achieved overall, which demonstrates that the synthesised samples were deemed to sound as realistic as genuine samples. These results demonstrate that the DCT representation is a valuable framework for analysis and synthesis of drum sounds. It is also likely that this approach could be applied to other instruments.

Applying a machine learning based object detector to high-speed videos of Caribbean steelpan drums illuminated by laser electronic speckle pattern interferometry (ESPI), we can track the development of sympathetic vibrations in response to drum strikes. This object detector was trained on a dataset of crowdsourced human-annotated images obtained in the Steelpan Vibrations Project on the Zooniverse platform. When the model is used to supply annotations to thousands of unlabeled video frames, we measure visual oscillations at frequencies consistent with audio recordings of these drum strikes. In this talk we share early physics results such as the unanticipated phenomenon of sympathetic oscillations of higher-octave notes that significantly precede the rise in sound intensity of the corresponding second harmonic tones; the mechanism responsible for this remains unidentified.

Swing, a popular technique in music performance, has been said to enhance the "groove" of the rhythm. Swing works by delaying the onsets of even-numbered subdivisions of each beat (e.g., 16th-note swing delays the onsets of the second and fourth 16th-note subdivisions of each quarter-note beat). The "swing magnitude" (loosely speaking, the amount of delay) is often quite small. And there has been little investigation, using musical stimuli, into what swing magnitudes listeners can detect. To that end, this study presented continually-looped electronic drum rhythms, with 16th-note swing in the hi-hat on every other bar, to drummers and non-drummers. Swing magnitude was adjusted using a staircase procedure, to determine the magnitude where the difference between swinging and not-swinging bars was just-noticeable. Different tempi (60 to 140 quarter-notes per minute) and swing densities (how often notes occurred at even-numbered subdivisions) were used. Results showed that all subjects could detect smaller swing magnitudes when swing density was higher, thus confirming a previous speculation that the perceptual salience of swing increases with swing density. The just-noticeable magnitudes of swing for drummers differed from those of non-drummers, in terms of both overall magnitude and sensitivity to tempo, thus prompting questions for further exploration.

The effects of air loading on the acoustical properties of tabla, an Indian musical drum, are investigated by idealizing it as a composite membrane backed by a rigid cylindrical cavity. The coupled boundary value problem for membrane vibration and acoustic pressure, assuming acoustic radiations to be the only source of dissipation, is solved using a Green's function method. It is shown that air loading helps in only fine tuning of the harmonicity of the composite membrane in the right hand tabla, but significantly improves the harmonicity in the left hand tabla. In both cases, it increases the decay time of the musically important modes. With a suitably defined error as the objective function, optimum tabla designs are found, which yield the most harmonic frequency spectrum. The obtained results are found to be consistent with the actual design of the tabla. Modal sound synthesis of the percussion instrument has also been attempted.

Additive manufacturing (3D printing) has seen tremendous growth over the past decade and is finding many fields of application, including in musical acoustics. Klapel Instruments has recently developed multiple snare drum prototypes using additive manufacturing production for the shell and rims of the drum. For the past two years, two pairs of undergraduates at the University of Hartford have worked with faculty to assess the acoustical properties of these drums, specifically focused on determining any acoustic differences caused by the new manufacturing technique and materials. Several traditionally manufactured drums along with the additively manufactured drums were tested structurally, performed on, audio recorded, and subjectively assessed. Modal, spectral, and subjective analysis along with a comparison between the drums created using additive manufacturing and the traditionally manufactured drums will be presented.

The vibration of a homogeneous circular membrane backed by two taut strings is shown to yield several harmonic overtones for a wide range of physical and geometric parameters. Such a membrane is present at each end of the barrel of an idakkā, an Indian snare drum well known for its rich musicality. The audio recordings of the musical drum are analyzed and a case is made for the strong sense of pitch associated with the drum. A computationally inexpensive model of the string-membrane interaction is proposed assuming the strings to be without inertia. The interaction essentially entails wrapping/unwrapping of the string around a curve on the deforming membrane unlike the colliding strings in Western snare drums. The range of parameters for which harmonicity is achieved is examined and is found to be conforming with what is used in actual drum playing and construction.

Snare drums and tom toms used in drum sets often produce an undesirable high frequency ringing sound when struck. Drummers have historically applied DIY damping solutions to address this ringing, placing objects such as wallets and tape on the heads. A large variety of inexpensive commercial products is now available to dampen drums in a more controlled manner. The most commonly used products consist of small adhesive pads that can be placed directly on the drumhead at desired locations, either singly or in combinations. An experimental investigation of the ringing drumhead modes and the effects of the damping pads is reported. Decay rate measurements indicate that the (3,1), (4,1), and (5,1) modes often contribute the most to the ringing sound, and that these modes are strongly affected by the damping pads. Another class of commercial dampener consists of thin annular rings of Mylar that conform to the perimeter of the drum head. These free-floating rings produce a similar damping effect, but dissipate e...

We present a machine learning computer program which applies a neural-network-based object detection algorithm to individual frames of high-speed video of oscillating Caribbean steelpan drums obtained via electronic speckle pattern interferometry (ESPI). This algorithm is trained in a supervised learning context on a dataset of crowd sourced human-annotated images obtained from the Zooniverse Steelpan Vibrations project. The computer code, which we call “SPNet,” is subsequently able to annotate new frames of similar images in a manner consistent with the humans' prior work, albeit much more quickly—hundreds of frames per second. The goal of this annotation work is to better understand the dynamical behavior of these drums such as the coupling of oscillations in different parts of the drum surface, by tracking the development of sympathetic vibration modes and extracting their relevant physics. We present details of the algorithm, performance metrics, and some preliminary physics results.

Electronic speckle pattern interferometry provides real-time images of operating deflection shapes of acoustically driven structures. This technique is particularly useful in the study of musical percussion instruments containing bars, plates, and membranes. Musically relevant examples involving drumheads, crotales, and the musical saw are presented. Imaging through water is described as well as methods for studying coupled vibrations between the two heads of a drum.

Mechanical musical instruments have a restricted timbre variability compared to electronic instruments. Overcoming this is the aim of extended playing techniques as well as building more sophisticated musical instruments in recent years. Metamaterials might be a way to extend timbre of mechanical instruments way beyond their present sound capabilities. To investigate such possibilities, a frame drum is manipulated to achieve different sounds. On the drum membrane of 40 cm diameter, a ring of masses is attached in three diameters, 8, 10, and 12 cm with 10 masses each, leading to a cloaking behaviour of vibrations from within the ring into the area outside the ring and vice versa, as shown by microphone-array and high-speed laser interferometry measurements. The resulting sounds have a band gap between about 300 and 400 Hz to about 700–800 Hz, depending on the ring diameter. The 8 cm diameter ring shows the strongest amplitude attenuation in the band gap. Still, when striking the membrane outside the ring, it sounds like a regular drum. This leads to a tremendously increased variability of musical articulations, especially when striking in the ring, as a band gap sound cannot be produced by a regular drum.Mechanical musical instruments have a restricted timbre variability compared to electronic instruments. Overcoming this is the aim of extended playing techniques as well as building more sophisticated musical instruments in recent years. Metamaterials might be a way to extend timbre of mechanical instruments way beyond their present sound capabilities. To investigate such possibilities, a frame drum is manipulated to achieve different sounds. On the drum membrane of 40 cm diameter, a ring of masses is attached in three diameters, 8, 10, and 12 cm with 10 masses each, leading to a cloaking behaviour of vibrations from within the ring into the area outside the ring and vice versa, as shown by microphone-array and high-speed laser interferometry measurements. The resulting sounds have a band gap between about 300 and 400 Hz to about 700–800 Hz, depending on the ring diameter. The 8 cm diameter ring shows the strongest amplitude attenuation in the band gap. Still, when striking the membrane outside the ring, ...

In the application of musical acoustics and speech sound, almost any type of Nigerian drum is used for communication. The agreeable successions of tones unlimited to interesting beat-patterns, pitch and rhythms uses shifted accents, non-accented rhythms, syncopations etc. On the daily basis of a watermelon harvesting and trade point, musical acoustics and speech sounds are applied passively in detecting and determining a ripen watermelon; the application of the Nigerian drum beat-pattern, pitch and intonation is an efficient procedure for ripeness detection of watermelon. Depending on how the pitches are lowered or accented, the melon ripeness is detected. The pitch-pattern analysis can be used to measure, determine and correlate the internal ripeness and quality of watermelon with pitch from a Nigerian drum. This method allows identification at a 60.0 % level of efficiency. Hence, the proposed method can reliably detect watermelon ripeness.

The Udu drum, sometimes called the water pot drum, is a traditional Nigerian instrument. Musicians who play the Udu exploit its aerophone and idiophone resonances. This paper will discuss an electrical equivalent circuit model for the Udu Utar, a modern innovation of the traditional Udu, to predict the low frequency aerophone resonances and will also present scanning laser vibrometer measurements to determine the mode shapes of the dominant idiophone resonances. These analyses not only provide an understanding of the unique sound of the Udu instrument but may also be used by instrument designers to create instruments with resonance frequencies at traditional musical intervals for the various tones produced and to create musical harmonic ratios. The information, specifically the laser vibrometry measurements, may also be useful to musicians in knowing the best places to strike the Udu to excite musical tones.

When a segment of a rigid duct wall is replaced by a membrane and is backed by a cavity, incident noise induces membrane vibrations and causes noise reflection. The reflection is effective over a broad band in the low-frequency region when a certain high tension is applied on the membrane in the axial direction of the duct. The device is thus called a drumlike silencer. The existing vibroacoustic theory is based on a two-dimensional duct model and the membrane is reduced to a one-dimensional string. This study extends the theory to three dimensions for the duct and two dimensions for the membrane which has all four edges fixed. It is shown, analytically, that the lateral tension is always detrimental to the silencing performance. However, the optimal performance of the one-dimensional string is recovered exactly when the lateral tension on the two-dimensional membrane vanishes despite the very different boundary conditions. The conclusion is validated experimentally, paving the way for the application of the drum silencer in which the cavity is completely separated from the gas flow in the duct.

The effectiveness and reliability of crowd-sourced data classification to study the acoustics of the steelpan was evaluated. A project was developed and hosted on the widely used Zooniverse website. Volunteers on the project’s site were asked to identify areas of maximum vibrations (called antinodes) and number of bright rings (fringes) in those areas for each classification. We explored various methods in ensuring volunteers generate successful classifications. The data for classification comes from a high-speed video recording, paired with Electronic Speckle Pattern Interferometry, of a strike on the steelpan’s surface, which produces thousands of frames to be analyzed. We developed the project in preparation for a public release. We have analyzed the collected classifications using imported Python libraries. After validation and averaging of volunteer classifications, an Amplitude vs. Time graph was obtained for each contributing note in the recording of a strike.

Bugles have long played an important role in American bands and corps, reaching beyond their military origins. As early as the 1920s, competitive drum and bugle corps performed in national competitions sponsored by the American Legion and the Veterans of Foreign Wars. Modern drum corps continue to compete through organizations such as Drum Corps International and Drum Corps Associates. While brass bugles in these competitive drum corps began as military signaling devices, successive modifications made them capable of greater ranges of music. These traditionally valveless, key-of-G bugles evolved to include pistons and rotors, gaining notes beyond a single harmonic series. Instrument sizes were varied to permit pitch ranges from contrabass to soprano. The corresponding music in these shows thus expanded from bugle calls to classical, jazz, and popular genres. This talk will trace the evolution of bugles and their capabilities in American drum corps from their 20th century history through the current day.

Acoustic principles of ErgoSonic Percussion's patented angled shell drums were studied through the Finite Element Method (FEM) predictions and acoustic measurements in our anechoic chamber. Unlike existing drums, this drum design provides improved playability and the ability to easily modify the resonant decay and character of the sound. When used in marching bands, this design is found to significantly reduce strain and fatigue of the musician. Computational and experimental results are presented to examine the effects of the shape of the drum, and the size, location, and orientation of a port on the resonant head on the pitch, sound decay and overall tuning of the instruments. This angled drum design is found to provide a smaller, lighter, and more ergonomic instrument that produces sound that is essentially equivalent to that of conventional drums. It is also shown that the acoustic properties of the port can be easily adjusted during use to significantly modify the resonant character of the sound by c...

In Korea, there is a rock with a wooden gong sound. It is the wooden gong rock of Pyochungsa Temple in Miryang, Gyeongsangnam-do, and drum rock of Palgongsan Mountain in Daegu. The wooden gong is one of the Buddhist ceremonial tools that make a sound by knocking an empty tree. In this paper, we will investigate which sound component of wooden gong rock and drum rock as a wooden gong sound through sound analysis. The wooden gong resonates at about 600 Hz when tapped and continues to sound for about 0.1 second. However, most stones and rocks have a sound duration of less than 0.3 seconds without any resonance. Pyochungsa Temple's Wooden gong rock resonates at about 600 Hz and shows a duration of 0.6 to 0.9 seconds, depending on the knocking position and strength. Palgongsan Mountain's Drum rock resonates at about 400 Hz and has a duration of about 0.5 seconds. We conducted a MOS test on 30 people to see how much sound like a wooden sound for each sound. The results were as follows: wooden gong 4.5, wooden g...

The objective of this work is to present an acoustic characterization of the chinchin, a bass drum type instrument native of Chile. The instrument is played by the chinchinero, an urban street performer in Chile, who dances acrobatically and plays the instrument simultaneously. Carried like to a backpack, the musician play the instrument with long drumsticks, which also involves a rope tied around the performer's foot to play the hi-hat cymbals. The string that drives the hi-hat cymbals passes through two holes in the cylindrical drum shell, modifying the expected sound of this type of instruments. We present detailed vibro-acoustic characterization in frequency and spatial domain using the Finite Element Method (FEM). Natural frequencies are compared with a usual bass-drum layout of similar dimensions as a baseline. Our preliminary results show differences in the fundamental frequency and the overtones of the chinchin bass drum are different from the normal one.

Physical modeling of musical instruments is of great interest, both due to the interpretation of the parameters that make the model as similar to reality as possible, and because of the faithful sound synthesis. In this paper we will focus on the modeling of percussion instruments and more concretely drums consisting of a vibrating membrane and a rigid body. One recently published physical model [S. Bilbao and C. J. Webb, J. Audio Eng. Soc. 61 (2013) 737-748] uses finite difference time domain schemes to solve both the system of equations describing the dynamics of the membrane, and the influence of the surrounding air. The main drawback of that approach is the growth of computation cost with the scale of the problem. A new approach is suggested here where an edge diffraction-based method [A. Asheim, U. P. Svensson, J. Acoust. Soc. Am. 133 (2013) 3681-3691] is used to compute both the air loading on the surface and the sound radiation. The finite difference time domain method is used in this approach too ...

In future hearing systems, one or more microphones and one or more receivers located within the earmold or ear canal are feasible. In order to predict the sound pressure at the ear drum in such a scenario, a one-dimensional electro-acoustic model of a prototype open earpiece with two integrated receivers and three integrated microphones was developed. The transducers were experimentally characterized by their (frequency-dependent) sensitivity (microphones) and Norton equivalents (receivers). The remaining acoustical system was modeled by 12 frequency-independent parameters which were fitted using a training set-up with well-defined loads at both sides of the ear piece. Put on an individual subject, the model could then be used to determine the acoustic impedance at the medial end of the earpiece, based on measured transfer functions between the integrated components. Subsequently, a model of the ear canal and its termination was estimated from the measured ear canal impedance, which could eventually be us...

We conducted a preliminary passive acoustic survey of the occurrence of freshwater drum in the New York State Canal System (NYSCS). Similar to more well studied marine members of the Sciaenidae, freshwater drum calls are composed of highly variable trains of 1 to 119 knocks/call (mean = 25 knocks/call), a mean knock period of 33 knocks/s, mean peak frequency of 400 Hz, and mean duration of 0.8 s. The occurrence of reproductively active freshwater drum, as evidenced by the presence of chorus calling throughout the canals, suggests that native drum populations from Lake Champlain, Lake Erie, and Lake Ontario likely all contribute to the Hudson River invasive population. We suggest that freshwater drum most likely also invaded the finger lakes through the NYSCS. The invasion of the Hudson River by freshwater drum is significant because the species had previously been geographically excluded from the entire east coast. It is a prolific species with the widest distribution of any native species in the Americas...

This study reports an onset detection method for the snare drum sounds for music signals constructed with plural instruments. We propose a method which detects an onset with a class separation using a deep neural network (DNN). To train the network, frames which include the waveform of the snare drum were extracted from music signal, and the log mel-filter bank channel outputs were calculated for each frame. The DNN was trained by using these feature parameters. The inputs were the calculated filter bank outputs, and the teaching signals were binary information whether to include the waveform of a snare drum or not. To detect onsets, candidate frames of the onset time were found based on changing in the power of the target music signal, and feature values were extracted from the candidate frames. Obtained values were used as the input data for the trained DNN, and detection of whether or not to include a waveform of a snare drum can be achieved. Experiments were conducted for 52 popular songs included in the music database, and an average F-measure was 0.73.

Sado is an island in the Sea of Japan. The population of the island is 57,114 (October 1, 2015). Sado had a gold mine and has a rich natural environment. It was also rich economically and many people came to Sado from many other places in Japan. People brought many entertainment styles to Sado. The traditional arts are still strong, such as Noh drama and Oni-Daiko ("ogre"drum performances). We have been active in Oni-Daiko performances in Toyooka village since 2009. The festival in Toyooka is held on the first or second Sunday of April every year. It begins in the Shrine of the enshrined deity of the village. We go around the houses in the village and come back to the shrine. It is performed in front of shrines and houses. The students perform it in public at the end of their one-week lesson. We perform it from 7 a.m. to 8 p.m. with the village people. Students mature after taking part in these activities. As the population of Sado begins to decline, we do not know how long we will be able to continue thi...

The tuning process of drums differ considerably between Western and Southeast Asian drums. While Western drums, like tom-toms, snare, or bass drums of a rock or jazz drum kit, are tuned by changing the tension of the drum head, many drums in Southeast Asia are tuned by adding a paste consisting of rice and ash. As an example, the tuning of the Myanmar pat wain, a unique drum circle of a hsain wain orchestra is investigated. The pat wain has 20 pitched drums and is played with great virtuosity. It was investigated by the author during a field trip in northern Myanmar during its tuning process. The drum head is modeled using a time-dependent Finite-Difference Method (FDM) to estimate pitch and mode changes due to adding the paste. The results are compared to the field recordings which show considerable damping and pitch glides with low-pitched drums. Also the tuning of the drum circle is compared to different tuning systems showing similarities to a tuning pattern of Cambodian roneat deik metalophone.

Electronic speckle-pattern interferometry (ESPI) provides a non-contact optical system that can be used to record images showing operating deflection shapes of structures being driven sinusoidally at resonant frequencies. In high-Q systems, these shapes can approximate the normal modes of the test object. Due to the sensitivity of the optical measurement system, non-contact excitation can be achieved acoustically using a speaker. The use of ESPI is described in relation to measurements of musical bars, plates, and membranes under various boundary conditions, though the methods described can be applied to many other types of structures. In addition, a dual-ESPI system that provides simultaneous measurements of two surfaces of an object is illustrated (e.g., two heads of a musical drum). These measurements provide information regarding the degree of coupling and the relative phase of the two vibrating surfaces. Finally, the ESPI techniques are applied to the fluid-structure interaction of an orchestral crot...

The cajon is a hand percussion instrument originally from Peru. Spanish for “large box” or “crate,” the cajon is typically a box enclosure with a thin wooden plate at the front that serves as the playing surface. Many resonance modes are excited when a player strikes the front plate, as recently studied by Pehmoeller and Ludwidgsen [J. Acoust. Soc. Am. 138, 1935 (2015)]. In this study, scanning laser Doppler vibrometry is coupled with high-resolution far-field directivity measurements to examine source vibration and the resultant sound field. Ties between the plate modal vibration and far-field sound radiation spatial patterns are shown. In particular, the non-uniform front plate normal velocities at higher-order resonances result in distinct nulls in the far-field directivity. Avoidance of these nulls yields recommended microphone locations for cajon sound amplification.

An implementation of a quarter-wavelength standing wave separator that exploits an air drum to achieve the pressure node is presented and characterized experimentally. The air drum configuration was implemented and tested in a set-up with a 40 kHz transducer immersed in a water tank with the quarter-wavelength gap being approximately 9 mm wide. Injection of suspensions of 5 μm and 45 μm diameter polystyrene particles at flow rates of 30 ml/h and 60 ml/h was studied and particle deflection towards the pressure node at the air drum surface was observed for a range of acoustic pressures. Computational results on single particle trajectories show good agreement with the experimental findings for the 45 μm particles, but not for the 5 μm particles. These were considered to behave as aggregates of higher effective dimension, due to their much higher number density relative to the 45 μm particles in the suspensions used. The set-up developed in this study includes a robust method for achieving a pressure node in a quarter-wavelength system and can represent the first step toward the development of an alternative separator configuration in respect to small channel MHz range operated systems for the manipulation of particles streams.

This paper uses modal analysis to investigate the effect of manipulating drumhead tension on the modal frequency ratios of a cylindrical drum with two drumheads. This analysis evaluates a drum’s free vibration after excitation. It is shown that the frequency of the (01) mode of the drum is the same on both heads, whereas the frequency of each (11) mode has a decreased dependence on that of the opposite drumhead. This allows manipulation of the ratios for the (11) modes of the batter and resonant heads with respect to the overall (01) mode. This manipulation is shown to allow a range of tunings such that the (11) mode of the batter head can be tuned to a ratio of 1.5× that of the (01) mode.

Modes of vibration, of a snare drum, as observed by holographic interferometry, impulsive modal analysis, and scanning with accelerometers, are related to vibrations of the drum heads, the shell, and the support stand. A simple two‐mass model correctly describes the lowest modes of vibration, but at the higher frequencies the drum heads vibrate more or less independently. Each mode of vibration radiates sound in a characteristic pattern which may have dipole, quadrupole, and higher multipole components. The snares move in a complex way, being in contact with the snare head during part of its cycle but losing contact at a later time and returning to strike the head.

The acoustics of a cavity‐backed composite membrane is analyzed under the assumptions that the cavity air pressure on the membrane is uniform, and hence sustains only axisymmetric membrane modes under impact excitation of the membrane. Axisymmetric modes of the membrane possess a harmonic relationship among themselves under certain parameter combinations. This mathematical model is chosen to explain the presence of harmonic overtones that are present in the Indian musical drum Mridanga, when struck with a characteristic stroke. Experimentally measured sound spectra from Mridanga when it is impact excited with different stroke patterns are also provided.

Sound pressure distributions in the human ear canal, whether unoccluded or occluded with ear molds, were studied using a probe tube technique. On average, for frequencies below 6 kHz, the measuring probe tube had to be placed within 8 mm of the vertical plane containing the top of the eardrum (TOD), determined optically, in order to obtain sound pressure magnitudes within 6 dB of "eardrum pressure." To obtain that accuracy in all of the eight subjects studied, the probe had to be within 6 mm of the TOD. Since probe location relative to the drum has to be known, a purely acoustic method was developed which can be conveniently used to localize the probe-tip position, utilizing the standing wave property of the sound pressure in the ear canal. The acoustically estimated "drum location" generally lay between the optically determined vertical planes containing the TOD and the umbo. On average, the "drum location" fell 1 mm medial to the TOD. Of the 32 estimates made acoustically in various occluded and unoccluded conditions in 14 subjects, 30 estimates lay within a +/- 2-mm range of this average.

Transient deformations can be observed by means of time-resolved electronic speckle pattern interferometry (trESPI), which implements a high-speed camera in the experimental setup and allows measurements of non-reproducible transients in real time. The stick-slip phenomena in musical instruments leads to transient nonlinear effects in the surface deformation, which can be resolved and characterized using trESPI. In this work, transient effects during the stick-slip motion of the Brazilian cuica drum are investigated. Measurements of the cuica under harmonic excitation and in playing conditions using trESPI are presented leading to a quantitative analysis of the motion.

Timpani, although limited in pitch material, have the ability to produce many subtle colors, exceeding most other membranophones. One of the most notable characteristics of timpani is the perceptual “bloom” of the sound as distance is increased with the drum. Timpanists spend many hours working on control of these sounds and the bloom through application of intricate mallet technique and striking location. Anecdotal evidence of these differences is passed down through generations of teachers and students, but very little objective data exists about the actual sound of the drums, and the variations that occur between players. This study endeavors to reveal the objective differences between players and techniques, particularly as it relates to the “bloom” of the sound as you move away from the drum. Control of this directivity and expansion of perceived sound at a distance may be the single most important factor in the quality of a timpanist’s sound. Measurements are taken at different distances and locatio...

I discuss the motivations behind the invention and production of my new drumhead tuning system. The design originated with the mridangam, an ancient and popular pitched drum from South India, which has been constructed the same way for centuries. The mridangam is notoriously difficult to tune and replace drumheads, which consists of multiple layers of leather and a complex iron oxide and starch loading. My new design makes tuning and head replacement more user-friendly and durable, and can be applied to any drum that needs to be fine-tuned. I present my research comparing the acoustics of the traditional mridangam design with my new design. I also explore the challenges and opportunities involved in the international manufacturing process that is currently underway. The presentation concludes with an interactive performance on the mridangam.

This presentation describes the redesign of an existing multi-purpose practice room used by high school concert bands, drumlines, and choral groups. Resource and cost restrictions limited the redesign and evaluation process for surface finishes only. The existing space had minimal early reflections and reverberation due to copious amounts of thick acoustic wall panels, resulting in a dead sound for choral and band use. The biggest challenge was to reposition the wall panels by distributing them in a checkerboard pattern, thereby balancing them with the reflective surfaces of the painted cinderblock underneath. In addition, one third of the absorptive suspended ceiling tile was replaced with 5/8” gypsum panels, and one third of the ceiling tile was removed altogether in order to couple the interstitial space above the suspended ceiling and increase the effective volume of the space. Odeon was used to create auralizations of various configurations by convolving anechoic recordings of a snare drum with the c...

The Aztecs and other cultures in Mesoamerica used to build and play during their festivities and warriors gatherings, simple drums made out from a hollow tree trunk, carved in the inside in order to make a fairly uniform thick surface to form the resonant chamber, topped by an ocelot skin, and open in the bottom, usually by three supports made from the same tree piece, called huehuetl, which means that these drums were of different shapes and sizes, some of these trunks were highly decorated by carving in the surface three dimensional images related to animals, faces, warriors, and other figures. These drums were excited on the top either by bare hand or wood sticks, varying the sound by the strength of the hit, and the area of the ocelot skin actually hit. Here are presented some pictures of ancient huehuetls together with the acoustic analysis of the sounds produced with a small replica of this percussion instrument.

Many musical drums, such as snare drums, bass drums, and tom toms, consist of two stretched membranes at opposite ends of a cylindrical shell. Vibrations of the two heads are coupled acoustically by the enclosed air and mechanically by the shell itself. The degree of coupling varies with modal frequency and shape, and depends on several factors including the geometry of the drum shell (diameter and length) and the tensions of the two heads. Experimental measurements of coupled vibrations on drums of various sizes have been made using an electronic speckle-pattern interferometer to image the deflection shapes, amplitudes, and relative phases of both heads simultaneously. These measurements are compared with a finite element model of the system that illuminates the role of the vibrational patterns of the enclosed air in the coupling process.

The percussion instruments family, in its folk category has many instruments like Dholki, Dimdi, Duff, Halagi, and Sambal. The Sambal is a folk membranophone made up of wood, played mainly in western India. Sambal a traditional drum, which is used in some religious functions. It is played by the people who are believed to be servants of goddess Mahalaxmi Devi. This instrument is made up of two approximately cylindrical wooden drums united along a common edge, having skin membranes stretched over their mouths. This instrument is played using two wooden sticks, of which one has a curved end. The right hand side drum’s pitch is higher than the left. Its membrane is excited by striking repeatedly to generate sound of a constant pitch. This paper relates to vibrational analysis of the Sambal. A study has been carried out to check it’s vibrational properties like modes of the vibration. The study is done by spectrum analysis (Fast Fourier Transform) using a simple Digital Storage Oscilloscope. The tonal quality of wood used for the cylinders and membrane is compared.

Traditional and matched grips have been compared using a series of measurements involving rhythmic sequences played by experienced jazz drummers using each of the two grips. Rhythmic sequences played on the snare drum were analyzed using high speed video as well as other measurement techniques including laser vibrometry and spectral analysis of the sound waveforms. The high speed video images, used with tracking software, allow observation of several aspects of stick-drum head interaction. These include two-dimensional trajectories of the drum stick tip, a detailed picture of the stick-drum head interaction, and velocities of both the stick and the drum head during the contact phase of the stroke. Differences between the two grips in timing during the rhythmic sequences were investigated, and differences in sound spectrum were also analyzed. Some factors that may be player dependent have been explored, such as the effect of tightness of the grip, but an effort has been made to concentrate on factors that are independent of the player. [Work supported by US National Science Foundation REU Grant PHY-1004860.]

An ultra-thin loudspeaker structure comprises an upper drum paper, a lower drum paper, and a steel sheet. The lower drum paper defines an opening at a center thereof and is integrally formed with a surrounding raised paper section near a periphery thereof. The upper drum paper defines an opening, corresponding to the opening of the lower drum paper, at a center thereof. The upper drum paper is located within the surrounding raised paper section and adhered to the lower drum paper by its periphery. The steel sheet is provided with a sound-making member stacked by a plurality of ceramic material layer, and is sandwiched between the drum papers. Accordingly, the steel sheet can facilitate spreading sound of high and medium frequency whereas the drum papers can facilitate spreading sound of low frequency, to achieve a better reproduction of sound.

An apparatus, method and computer program, the apparatus comprising: including a loudspeaker configured to convert an electrical input signal into an acoustic output signal; a connecting portion configured to interchangeably connect to either a first adapter or a second adapter where the first adapter is configured to fit in a user's ear canal and the second adapter is configured to fit to a user's concha; and a regulator for regulating sound pressure level created by the acoustic output signal at an ear drum of the user in dependence on whether the first adapter or the second adapter is connected to the connecting portion.

Ancient percussion instruments in Mesoamerica included the Huehuetl and the Teponaztli, both made out of a single piece of hollow trees, which pretty often were decorated with low profile representations of animals, warriors or other ceremonial symbols, both were often used by the Aztecs and Tarascas among many other cultures in the region. The first one is normally used in a vertical position and has an strained animal skin, typically an ocelot, in the top side in order to excite it with wooden sticks or by the bare hands, while the second is formed by a couple of tongues made out from the same tree cortex, and excited by a couple of wooden sticks covered with hard rubber. In both the hollowed tree forms a resonant chamber in order to increase the sound level, and include openings in order to allow the exit of the sound from inside of the drum. They were employed for ceremonies, festivities and communication. Here, there are presented the sound characteristics of a small “teponaztli,” which is actually a small copy scaled about 5:1 of a real one, which can usually only be seen in archaeological museums.

This paper is proposed about reducing the transient vibration of drum type washing machine. The vibration of washing machine is caused by unbalanced cloths in high spinning drum, and the displacement of tub is maximized at transient range about 3 Hz (180 rpm). The dynamic model of washing machine is include a diaphragm. In this study, the displacement of tub is decreased by using gyroscope system. Multibody dynamic model ofwashing machine include gyroscope is designed and the vibration of tub have been reduced by the gyroscope system.

With advancements in manufacturability and increasing accessibility of materials, composite materials are competing with traditional materials in the design and manufacturing of musical instruments. Specifically, in snare drum applications, carbon fiber encased in an epoxy matrix has been chosen for its physical properties of strength, durability, and weight as well as its psychoacoustic properties compared to wood. Through comparative data acquisition analysis, the acoustic properties of composite snare drum shells are examined against traditional wooden snare shells. By subjecting the shells to controlled audio frequencies, the sound energy response on the air medium outside of the shell was measured and compared to wooden shells. Experimental data were examined was compared to theoretical values found for carbon fiber.

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.

Many musical drums such as snare drums, tom toms, and bass drums consist of two membranes at opposite ends of a cylindrical shell. Striking one head causes both to vibrate, as their motions are coupled due to the enclosed air as well as the shell itself. An optical system consisting of two electronic speckle-pattern interferometers was constructed allowing operating deflection shapes of both heads to be viewed simultaneously while the drum is driven acoustically at a resonant frequency. This system allows the determination of the relative phases, orientations, and amplitudes of the vibrational patterns on the two heads. Previously reported results for coupled drumheads were verified and extended to include the effects of degenerate single membrane mode pairs that are split due to non-uniform tension in the heads. Examples of higher frequency coupled patterns are also shown. Parameters influencing the degree of coupling are described briefly and compared qualitatively with results from a finite element model.

Percussion instruments and interfaces can be extended by incorporating actuation with motors. While many prior designs have employed actuation to simply trigger notes, this work emphasizes the importance of the musician's gesture using expressively controlled actuators. This is achieved by implementing force-feedback control of the actuators. For example, the Haptic Drum essentially consists of a drum pad attached to a woofer. Every time that a drumstick strikes the drum pad, the woofer briefly pushes it upward again, adding energy to the motion of the drumstick. In this manner, the Haptic Drum enables musicians to play one-handed drum rolls at optionally superhuman speeds and with arbitrarily complex dynamics. Furthermore, because the musician and the drumstick are inside the feedback control loop, the musician can change the rate of the drum roll by modulating the stiffness of his or her muscles or changing the downward force applied to the drumstick. Conversely, borrowing on technology for remote surgery, expressively actuated percussion instruments can be designed using force-feedback teleoperation. Simply by recording the position of the master haptic device during teleoperation, generalized motor programs can be created for expressively playing percussion instruments. This technology was employed in the composition “When the Robots Get Loose."