bluuebunny/crossref_metadata_2025 huggingface dataset:
Closed-loop finite-element modeling of smart structures—An overview
Authors: Varadan Vasundara V. , Lim Young-hun , Gopinathan Senthil V. , Varadan Vijay K.
Published: July 2002

Smart structures incorporate sensors, actuators, and control electronics that permit the structure to tailor its response to changes in the environment in an optimal fashion. The sensors and actuators are constructed using functional materials such as piezoelectric materials. Finite-element modeling has been successfully used to model these complex structures. More recently, closed-loop numerical simulation of the tailored response of a smart structure has become possible by combining the finite-element equations of the sensor response to applied dynamical loads to the input voltage or current to the actuators via a control algorithm. Optimization of sensor/actuator placement as well as optimization of the control gains will be discussed. Applications to control of cabin noise are studied. Constrained layer damping, incorporating active passive damping, can also be simulated. The talk will present an overview of the approach in relation to others in the extant literature.
Developments in active control of aircraft interior noise—Directions for tonal and broadband noise sources
Authors: Silcox Richard J.
Published: July 2002

Aircraft interior noise is a continuing problem for a wide range of aircraft types. Interior noise levels in general aviation aircraft make communication difficult, significantly impact pilot endurance, and are considered important to the reemergence of this class of aircraft. For passengers in propeller-powered commuter aircraft, conversation is difficult at best and becomes oppressive on the passengers for long periods. It is also regarded as one reason for the replacement of propeller commuter aircraft by the emerging regional jet. In business jets, the passengers are often interested in conducting meetings during flights. This calls for low SPL and SIL for which the aircraft incurs both space and weight penalties. Large commercial aircraft pay a significant weight penalty for current interior noise levels considered acceptable. With the drive for more weight-effective airframes, the challenge becomes even more difficult. This paper will show some current efforts to develop more efficient active control technologies for both tonal noise sources and broadband noise sources. These will include improvements in controller technologies, actuator implementation, optimization of transducer topology, improved coupling to the noise source, and integration of the active technology with conventional passive technology.
A multichannel active system for control of the booming inside a van
Authors: Bravo Teresa , Cobo Pedro , Martin Juan Manuel
Published: July 2002

The van under study presents a problem of booming when the engine periodic noise excites some low-frequency modes of the cabin. The aim of this work is the design and implementation of a multichannel active system to alleviate this problem. First, a reference signal is searched correlated with the noise measured by a microphone in the driver head position. The best reference signal is the longitudinal vibration picked up by an accelerometer under the differential group. Then, the acoustic field inside the van is modeled by the normal modes theory. Optimization by simulated annealing allows one to find the best locations for six loudspeakers and six microphones. Finally, the multichannel active noise control is implemented by using a commercial system. Measurements of noise reduction have been carried out in the semianechoic room at NECT-E under usual driving conditions (third gear, slow acceleration). [Work supported by CICYT, Project AMB97-1175-C03-01.]
Modeling the alignment of fundamental frequency contours
Authors: van Santen Jan P. H. , Möbius Bernd
Published: July 2002

Segmental factors can cause large temporal changes in local fundamental frequency (F0) movements associated with accented syllables (‘‘accent curves’’), but these changes are often not phonologically or perceptually significant. Yet, other factors can cause temporal changes that are smaller but nevertheless significant. A model is proposed according to which accent curves are (phonologically, perceptually) equivalent when they are generated from a common accent curve template using a common set of alignment rules. These alignment rules specify where the points making up the template are to be placed on the time axis, based on the durations of the segments in the syllable sequence with which the accent curve is associated. This model is shown to provide a detailed and accurate account of alignment of accent curves over a wide range of segmental configurations. The model is embedded in a superpositional framework, in which accent curves, segmental perturbation curves, and phrase curves are combined to account for complicated surface F0 contours. Height of accent curves is determined via a multiplicative model from factors related to prominence and position in the phrase.
Instrumental speech-quality measures: New insights, ideas, and results
Authors: Heute Ulrich
Published: July 2002

Two bases for instrumental quality measurements in speech transmission are well known: comparison between (i) distorted and undistorted signals and (ii) distortion and undistorted signal. Revisiting an approach on the latter basis, combined with a quality-attribute matching [U. Halka and U. Heute, Speech Commun. 11, 15–30 (1992)], the drawbacks of long-term system characterization, too many degrees of freedom, and, especially, this basis itself are addressed. The first basis and several psychoacoustically motivated variants are then discussed. Thorough investigations of applicability and negligibility of psychoacoustical knowledge show that good modeling is indeed useful [M. Hauenstein, DSP Research Series, No. 10, Shaker-Verlag Aachen (1997) (in German)], in contrast to earlier statements, despite the extra computations needed. Returning to the idea of separating certain system characteristics (like linear distortions or frequency shifts) as partially done in the first quoted work, a completely different consideration turns out to be valuable: Instead of adding them as parts of the (possibly nonlinearly) combined distortions, their determination may be used to remove them from the measure as (partially) insignificant effects [J. Berger, DSP Research Series, No. 13, Shaker-Verlag Aachen (1998) (in German)]. New measures derived from these thoughts are presented and compared to other methods.
Influence of the direction of a single reflection on speech intelligibility
Authors: Brüggen Marc
Published: July 2002

Speech intelligibility in a complex environment such as a room is affected not only by competing sound sources but also by reflections off walls, the ceiling, or the floor. In this context, the benefit of early reflections for intelligibility in rooms has been demonstrated principally. In which way the auditory system achieves this improvement is still a matter of discussion. Therefore, a speech comprehensibility test was performed in a simulated scenario. Each stimulus consists of a speech target sound that emanates from a 45° azimuth direction and competes with a noise source at −45° azimuth. Both are in the horizontal plane. The speech target is accompanied by a single reflection adjusted in time-delay and level relative to the primary sound to be beneficial for intelligibility [e.g., Nabelek and Robinette, J. Acoust. Soc. Am. 63, 187–194 (1978)]. During the tests, the variable under investigation was the direction of the reflection. Speech comprehensibility was measured with an open response paradigm utilizing meaningless one-syllable words as speech material. The direction-dependent results indicate an interaction of influences in accordance with earlier findings.
Error analysis concerning the directional resolution of space-apart four-microphone probes
Authors: Odjijdja H. , Krämer P.
Published: July 2002

For room acoustical measurements, the direction of incident sound waves and reflections is of great interest. With space-apart four-microphone probes, the direction can be evaluated by analyzing the differences in propagation time of discrete reflection patterns. The microphone positions can have different spatial arrangements (Cartesian, tetrahedron). The directional resolution depends highly on the exactness of the evaluated propagation time between the microphones. Important factors influencing the calculation of the propagation time are the sound velocity and the distances between the single microphones. Starting from the assumption of constant tolerances of these factors, the error analysis of the directional resolution has been carried out for several kinds of spatial microphone arrangements. The calculation is based on a simple model (plane wave propagation) as well as on a more general attempt (considering the exact location of the source). The actual resolution is dependent on the incident direction. Nevertheless, the magnitude of the error considering all directions is nearly the same for the investigated arrangements.
The effect of grease ice formation on ambient noise
Authors: Johannessen Ola M. , Sagen Hanne
Published: July 2002

During cooling, a very thin visco-elastic film of ice, grease ice, can be formed over large areas of the marginal ice zone. This thin layer of ice has been observed to dampen out the shorter surface waves, which in turn reduces the ambient noise level. Ambient noise recordings made by a bottom-mounted buoy and sonobuoys during SIZEX 92 showed that grease ice causes a 9-dB stronger reduction close to the seafloor than in recordings made 18 m below sea surface. The topic of this presentation is to show why the grease ice causes a stronger dampening of the ambient noise close to the sea floor than close to the surface. The major result of the study is that the wave dampening effect of the grease ice accounts only for around half the reduction of the ambient noise. The other half is caused by a creation or enhancement of a surface duct prior to the grease ice formation which causes sound above around 100 Hz to be trapped close to the surface. These results illustrate how ambient noise characteristics are shaped partly by the noise-generating processes and partly by propagation effects.
Sound level differences in shafts—Measurements in the IAB laboratory
Authors: Kurz Andreas , Schroeter Knut , Teuber Wolfgang
Published: July 2002

The sound isolation between rooms can be lowered by the implementation of additional sound paths, e.g., by sound transmission via shafts. Above all, this applies to shafts which have openings to the adjacent rooms. With a normal metal duct and with certain outlets, the sound isolation was measured when a sound dampener was additionally implemented into the duct. The openings of the outlets were changed, then the level difference and the isolation index were measured. The construction of the test facility will be described.
An algorithm for auralization of airborne sound insulation
Authors: Thaden Rainer
Published: July 2002

On the basis of a prediction model for airborne sound insulation (EN 12354-1), a signal processing tool was developed for auralization of indoor and outdoor noise in receiving rooms. For this purpose the direct transmission and four flanking paths were taken into account according to their one-third octave band data. These energy components were addressed to specific field situations in the receiving room with specific delays and directions. The directions of the five transmission paths as well as the reverberation tail were treated binaurally. A large number of building elements can be simulated with nine different hearing rooms. The algorithm was implemented in C (and partly in Assembler). Typical processing time for generation of a 20-s audio file is approximately 10 s on a Pentium II with 233 MHz. Typical time signals, frequency responses, and some sound examples will be presented illustrating this algorithm. This work was done in cooperation with the PTB and supported by Gruenzweig and Hartmann AG.
Low-frequency impact sound transmission through floor systems
Authors: Warnock Alf
Published: July 2002

An extensive series of measurements of airborne and impact sound insulation on joist floors of various types was recently completed at NRC. About 190 floors with different joist types, subfloors, ceiling types, ceiling support systems, and type and thickness of sound absorber were constructed and sound insulation measured to frequencies lower than required by standards. The joist types comprised solid wood, wood trusses, I-joists, and steel joists. Glass, rock, and cellulose fiber sound-absorbing materials were used. Three concrete slabs were included in the series and a few of the joist floors had concrete toppings installed. Impact devices used on the floors included the standard ISO/ASTM E492 tapping machine, a walker, a JIS 1419 tire impactor, and two experimental rubber balls. The impact measurements provide an extensive, consistent set for examining alternative impact tests and possible modifications to standard tests using the ISO tapping machine. Correlations among the sound levels from the different impactors show that levels from the ISO tapping machine correlate well with those from a walker at low frequencies although the spectra are quite different in shape. The data and the prospects for a new test method and rating system will be discussed.
Additional improvement of airborne and impact sound insulation of ceilings in prefabricated standard house-buildings
Authors: Küstner Eberhard , Krämer Peter S. , Scholze Jürgen , Sonntag Ernst
Published: July 2002

Earlier studies for the improvement on airborne and impact noise insulation of ceilings in prefabricated standard house-buildings has been continued by the support of the German Ministery of Building. The investigated slab blocks were erected in 1987 in Potsdam. The raw ceilings made of solid concrete have a thickness of 140 mm. These realized ceilings have a weighted airborne sound insulation of Rw′=49 dB and a normalized impact-sound pressure level of Ln,w′=77 dB (averaged over nine measurements). A selection of floating floor materials were built in and measured: dry laser constructions (with plaster and compound cement slabs), asphalt applied by melting, and anhydrite layers. The aim of the project was to fulfill the requirements (Rw′=54 dB, Ln,w′=53 dB) of German Standard DIN 4109 from 1989, minimizing construction height and cost. Based on earlier studies (Scholze, DAGA ’94) all floating floors with a height larger than 45 mm (asphalt floor 40 mm) have been improved to reach the requirements of DIN 4109. Using mineral wool as sound insulation material below the floating floor gave results up to Rw′=56 dB (maximum value) and Ln,w′=48 dB.
Towards a classification of acoustic comfort. A case study of a university classroom
Authors: Rodriguez-Manzo Fausto
Published: July 2002

When it comes to speaking about acoustic comfort, one is generally dealing with a concept implying high levels of subjectivity. Hence, it becomes difficult to distinguish precisely the borderline between comfort and acoustical annoyance for an activity in a given space. Acoustical classification tools such as noise rating, noise criteria, preferred noise criteria, room criteria, balanced noise criteria, sound transmission class, and impact insulation class have proved to be partially useful in establishing averages of comfort in rooms, regardless of the spectral quality, which is intimately related to the acoustic quality of the room, and in turn related to the architectural comfort of the environment. This paper deals with the problem of correlating the quantitative aspects of acoustical measurements with elements of subjective perception. An accurate rating of the subjective acceptability of noise by polling the students, together with a simultaneous measurement of physical parameters, would result in a more realistic measure of acoustic comfort. Thus, the design of a method to correlate these parameters for the particular case of a university classroom is presented.
Time resolution of the dolphin’s auditory system: Better than 20 microseconds?
Authors: Zaslavski Gennadi L.
Published: July 2002

The time resolution of the dolphin’s sonar estimated as a minimum interval between echo highlights at which the dolphin is still capable of distinguishing the targets, ranges from 10 to around 300 microseconds. The problem, however, is that the target echo highlights are highly correlated and produce regularly spaced ripples in the amplitude spectrum. It is not clear whether the dolphins discriminated between a target’s echo in the time or frequency domain. Unless special measures are taken to eliminate this equivocalness, the experimental results can be equally accounted for discrimination cues in either domain. Different techniques were used to eliminate frequency discrimination cues that could be used by a dolphin. The double clicks that were designed differed in interpulse interval despite their long-term amplitude spectra being identical, and the highly correlated double clicks were replaced with the uncorrelated noise double pulses [G. Zaslavskiy, Proc. I.O.A. 19, Pt. 9]. The dolphin’s auditory system time resolution was found to be 25 to 30 microseconds. In this presentation the new measurement of the dolphin’s time resolution of 17 to 25 microseconds will be discussed. The time resolution was estimated as a minimum delay of the click from onset of the noise or tone pulse just detectable by the dolphin.
Improved signal processing techniques for measurement of the interpulse interval (IPI) of sperm whale clicks
Authors: Hayward Thomas J. , Pavan G.
Published: July 2002

Improved signal processing techniques are described for estimating the interpulse interval (IPI) associated with the multiple pulses in a sperm whale click. These pulses are believed to result from repeated reflections of the original pulse within the spermaceti organ in the whale’s head. Previous estimates of the IPI have been based on time series correlation or on computation of the cepstrum of the received waveform [J. Goold, J. Acoust. Soc. Am. 100, 3431–3441 (1997)]. The present work describes real-time computation and display of the spectrogram and cepstrogram (time-cepstral distribution) [G. Pavan, Proc. IOA 19(9) (1997)] and examines the benefits of the simultaneous display of this information for field analysis and for browsing long recordings to identify sperm whale clicks. In addition, a detailed model of the spectral modulation associated with the multiple pulses is developed and leads to improved estimation of the IPI. Examples are presented that indicate the method may be more robust with respect to additive noise and the effects of surface reflection than the cepstrum-based approaches. [Work of the first author supported by ONR. Work of the second author supported by the University of Pavia, Italy, the Italian Ministry of the Environment, and by the Italian Navy.]
The role of international and European standardization in relation to European directives
Authors: Nielsen Leif
Published: July 2002

There are three different types of relations between standards and EU directives: (1) Self-contained directives: Basically such directives do not call for standards. However, though standards do not contain noise limits, many standardized measurement methods exist, and much work has been initiated in order to avoid conflicting measurement methods in directives and standards. (2) ‘‘Reference to standards:’’ Such directives may, e.g., contain noise limits, and measurement methods are given by direct reference to specific standards which may be international or European. (3) ‘‘New approach:’’ This is the most modern way of using standards in relation to directives. Such directives contain only so-called ‘‘essential requirements’’ leaving the technical content to be fulfilled by standards. Standards in this context are required by the EU Commission to be European standards prepared by CEN. The most well-known example is the machinery safety directive. This has lead to the preparation of some 400 safety standards containing noise paragraphs. The EU commission has just started preparing a directive on external noise. Many standardization activities are also going on in this area. At the moment it is not known which type of directive is intended and which role the international and European standardization work will have.
New trends in standards indicate need for more interlaboratory comparisons and data
Authors: Nedzelnitsky Victor
Published: July 2002

Current trends in standards development now place, and will continue to place, significantly increased demands on laboratories around the world. Shorter IEC/ISO procedural deadlines and the increasing pace and complexity of standards development require that more work be accomplished in less time. Several trends account for the increasing complexity of measuring instrument standards from IEC TC 29 electroacoustics. One trend is the breadth and rapidity of technological developments in transducers and modern analog/digital electronics. Other trends involve the inclusion in standards of more information regarding uncertainties, test methods, procedures, and EMC (electromagnetic compatibility). This information is needed because these IEC standards are being used to support development of OIML recommendations in legal metrology, as well as national and regional standards and regulations in many countries. The need to produce correct statements regarding measurement uncertainties, methods, and procedures greatly increases the need to acquire extensive, reliable data, especially from interlaboratory comparisons, both for the preparation of new standards, and for the necessary periodic revision of existing ones. Finding resources to meet this need is an important challenge for the field of acoustics. Activities begun in BIPM and other organizations will provide data for primary (but not necessarily secondary) acoustical metrology.
Development and evaluation of an adaptive loudness scaling procedure
Authors: Brand Thomas , Hohmann Volker
Published: July 2002

Loudness scaling procedures are used in the diagnostics of hearing impairment to assess the recruitment phenomenon, i.e., the pathological growth of loudness. In these procedures, acoustical stimuli at different levels are presented to the subject and the task is to rate the perceived loudness on a category scale. The aim of this study is the development and evaluation of an adaptive loudness scaling procedure in which the level of the next stimulus is calculated on the basis of the previous trials. Based on empirical results from normal-hearing and hearing-impaired listeners, the procedure was optimized in order to yield minimal test–retest deviations and minimal biases due to range and context effects at minimum measuring time. To achieve these aims, different settings of the following parameters were tested: Number of response alternatives, track length, initial level, adaptive procedure, and parametrization of the loudness function. The best setting was shown to yield an equal distribution of stimulus levels in the full dynamic range of the individual subject with a minimum number of ‘‘inaudible’’ and ‘‘too loud’’ presentations. For each categorial loudness the corresponding stimulus level is estimated with a standard deviation of about 5 dB.
Zonal and global control of structural intensity in an infinite elastic plate
Authors: Hayek Sabih I. , Won Jungyun , Kim Giman
Published: July 2002

In a previous paper, the active control of active structural intensity (SI) in an infinite elastic plate was discussed. The plate is excited by mechanical noise sources, which generate a vector active SI field in the plate. A colocated point force and a point moment actuator at an arbitrary location on the plate were used. An algorithm was developed to minimize the active SI at a reference point on the plate. The control strategy was aimed at minimization of only the SI at a reference point. In this paper, the active control of SI in a desired zone or a large global area of the plate is explored through the use of multiple controllers spread over the plate. Furthermore, the cost function to be minimized also includes the required power injected by the controllers. Thus the minimization algorithm minimizes both the total SI in a zone as well as the total injected power by the controllers. The influence of the number and type of controllers, and the location of these controllers relative to the source region for the minimization of both the total SI in a region and the input mechanical power of these controllers, is explored. a)Currently Visiting Scholar at Penn State Univ.
A comparison between active and semi-active global vibration control of structures
Authors: Brennan Michael J. , Dayou Jedol
Published: July 2002

Semi-active devices, such as tunable vibration neutralizers, have been used for a number of years to control structural vibration at the point where the device is attached to the structure. More recently there has been some work on the use of these devices to control the global vibration of a structure and hence the radiated sound. In parallel with this, research has been conducted on the active control of sound radiation from structures. Because there are a number of advantages in using semi-active rather than fully active control in terms of cost and complexity, it is important to be able to quantify the benefits of each strategy on the global control of vibration. The aim of this paper, therefore, is to compare the effectiveness of the two control strategies by focusing on a simple structure such as a beam. Simulations will be presented to show that, provided the dynamic behavior of the structure and the semi-active device are known, then a semi-active device can be appropriately positioned so that it will perform almost as well as the fully active system. Moreover, it will be shown that a simple local control strategy can be employed provided that the device is positioned correctly.
Compact, inexpensive, analog robust controller modules for cabin noise control
Authors: Varadan Vasundara V. , Sreenivasan Ramanathan , Chang Woosuk , Varadan Vijay K.
Published: July 2002

Control of noise in an enclosure when the noise source is exterior to the enclosure has applications to rooms, automobiles, helicopters, airplanes, and other vehicles. Reducing the interior noise to acceptable levels is necessary for safety and comfort. One approach to control of interior noise is through vibration suppression of the trim panels that often line the interior of such enclosures. It is ultimately these trim panels that reradiate the noise to the interior. In order to actively control the vibrations of the trim panels, using discrete piezoelectric sensors and actuators, control electronics are needed. Adaptive digital control, while being efficient and powerful, also requires the presence of a computer and DSP boards. There may also be frequency limitations posed by the speed of available DSP boards. An alternative approach is to design compact and inexpensive analog controller units, which also offers the possibility of having such controllers designed as ASIC chips. To demonstrate the efficacy of this approach, results will be presented for the control of noise in a cabin with multiple trim panels when excited by broadband noise from the exterior using MEMS vibration sensors and PZT actuators.
Mosquito bioacoustics: Microscanning laser vibrometry of sound-induced antennal vibrations
Authors: Goepfert Martin C. , Robert Daniel
Published: July 2002

The acoustically oriented mate-finding behavior of mosquitoes is a classic acoustic near-field detection and communication system. Male mosquitoes are attracted by the female flight sound, and previous studies [H. Tischner and A. Schief, Zool. Anz. Suppl. 18, 453–460 (1955)] indicated that the male antenna enters resonance in response to these sounds. Microscanning laser vibrometry was used to document the biomechanics of antennal sound detection in Aedes aegypti. Measurements confirm that the antenna acts as a velocity receiver with the antennal shaft rocking about its socket in a rodlike manner. The frequency response of the male antenna, revealed by white-noise analysis, shows maximum velocities around 500 Hz corresponding to the dominant frequency emitted by flying conspecific females. The female antenna, however, is not tuned to the male flight sounds, suggesting that only males use incident sounds for mate detection. The function of sound-induced antennal vibrations in females remains unclear. Further comparative analysis focusing on the directionality of the antennal response and sound emission will be presented. [Work supported by the Deutscher Akademischer Austauschdienst and the Swiss Science Foundation.]
A hybrid model for echo prediction in coastal waters
Authors: Chevret Patrick
Published: July 2002

Echo prediction in coastal waters is a complex task due to the fact that a very wide range of scales is involved in the propagation and the scattering phenomena. The model developed is based on a separate formulation of the propagation and the scattering aspects and a coupling procedure. The propagation modeling is performed using a high-order parabolic operator; it is used from the source to the vicinity of the target. At this step, the field is decomposed in a set of plane waves that are scattered by the target (decomposition on the target mode). The reflected plane waves are then propagated back to the receiver. This global approach can be considered, somehow, as an ‘‘exact one,’’ nevertheless it is limited to simple shapes and is very time consuming. A simplified formulation has been developed in parallel that avoids the coupling problem by computing separately the medium and the target response. The free-field echo of the target (monostatic response) can be either a numerical or an experimental one. The final echo is obtained by the convolution of both responses. Both model’s performances are compared (computation time, accuracy, ...).
Detecting, mapping, sampling, and analyzing oceanic suspended particulate matter: Methods complementary to acoustic detection of environmentally sensitive ocean outfall and dumped materials
Authors: Nelsen Terry A. , Proni John R.
Published: July 2002

Natural systems such as lakes, rivers, and oceans can be described by dissolved and particulate components. Particulate sources in coastal oceanic environments include natural materials from seaward riverine and estuarine flows and anthropogenic sources such as ocean dumping and outfalls. Plumes of suspended particulate matter (SPM) can be natural (lithogenic and biogenic), anthropogenic, and any mixture of these. Because SPM can range from environmentally neutral (i.e., lithogenic and biogenic) to hazardous (heavy metals, bacteria,...), detecting, tracking, sampling, and sourcing SPM plumes can be beneficial for the environment and human health. Acoustic methods have proven successful in detecting and mapping oceanic SPM over large spatial areas but are limited in resolving internal fine structure, estimating relative contributions of merged plumes from various sources (e.g., river outflow versus dumping), and differentiating between introduced and in situ SPM. To complement acoustics, CTD/optical/water survey tools have been employed for guided sampling of plumes. Water samples for total suspended matter (TSM) and particle size distributions have proven useful both to calibrate acoustic measurements and provide insight into signatures provided by particle size distributions. Signatures, determined by factor and component analyses, allow mapping of SPM components as well as estimating their dilution and long-termed budgets.
Radio-frequency surface acoustic wave filters for mobile communications systems
Authors: Rösler Ulrike , Ruile Werner , Ruppel Clemens C. W.
Published: July 2002

Surface acoustic wave (SAW) filters are small, rugged, crystal stable, and can be fabricated with high reproducibility. SAW filters play a key role in the rapidly growing market of mobile communication systems and are used for channel filtering as well as for RF filtering. For today’s communications systems novel types of SAW filters are being developed in order to meet the stringent requirements with respect to low insertion loss, high relative bandwidths, good stopband rejection properties, and power durability. Most SAW RF filters are fabricated on cuts of LiTaO3 and LiNbO3. To obtain very low loss filters precise knowledge of the wave propagation and loss mechanisms is a prerequisite. Using advanced analysis tools, substrate-cut-metallization combinations can be chosen for minimized propagation losses. To enhance power durability of SAW filters both substrate-metallization combination as well as the design have to be optimized. Two different filter techniques are used for SAW RF filters. The working principles of double mode structure (DMS) filters and ladder-type filters, both using resonances to minimize the lengths of the structures and the required chip size, will be described. As examples, RF filters for GSM and PCN, diplexer for GSM, and duplexers for cordless phones will be presented.
Measurements of arm motion, timing, and striking force in a simple drumming task
Authors: Dahl Sofia , Stokes Virgil P.
Published: July 2002

How does the percussionist’s playing technique and feedback from the instrument influence the performance with respect to timing and striking force? In an attempt to answer this question the motion of the right arm and drumstick, and the timing and striking force in a simple repeated drumming task were measured for three professional percussionists and one amateur. The task consisted of single strokes with interleaved accents played at three different tempi and at three dynamic levels. Three striking tools (drumsticks, mallets, and brushes) and three different types of striking surfaces were used. Differences between the players’ performances under the different experimental conditions will be reported. [Work supported by the Bank of Sweden Tercentenary Foundation.]
Time relations between harmonics of violin tones in dependence on playing techniques
Authors: Volný Petr , Štěpánek Jan , Syrový Václav
Published: July 2002

Particular violin tones were played by a professional violin player in an anechoic room. The tones from the whole violin range, played nonvibrato using selected bowing techniques (naturale, sul ponticello, sul tasto) and dynamics of playing (p, mf, f), were recorded. The analysis based on the short-time Fourier transform was used to compute the time courses of amplitudes and frequencies of separated harmonics from the SPL recordings of the tones. The time characteristics of the time envelopes of the whole tone and his harmonics were calculated in the next step. For example, attack time, decay time, and relative starting time were studied. The influence of playing techniques, dynamics, and tone pitch on these time characteristics was described.
Diagnosing dead spots of electric guitars and basses by measuring the mechanical conductance
Authors: Fleischer Helmut
Published: July 2002

The ‘‘sustain’’ of the string signal is considered as a quality attribute of an electric plucked instrument. In musical practice, distinct locations are observed on the fretbroad where a string decays faster than at adjacent frets. Such ‘‘dead spots’’ originate from the fact that the string may cause the neck to vibrate. Energy flows from the string to the neck with the consequence that the string vibration decays irregularly fast. Experiments were performed with the aim of finding a measuring approach for the diagnosis of dead spots in terms of the vibration willingness of the neck. Various parameters (decay rate, surface velocity, admittance) were ascertained for a series of electric guitars and basses. Special care was taken to ensure comparable and ‘‘natural’’ boundary conditions. Measuring the mechanical conductance (i.e., the real part of the point admittance) on the neck with the instrument held in normal playing position proved a straightforward and reliable method for the diagnosis of dead spots. The measuring procedure and instrumentation will be presented. Typical results will be given in a compact 3-D representation (conductance versus frequency for each fret), evaluated and related as well to the decay rates as to the vibrations of the instrument body.
Polarity of noise and musical tone in a phenomenological point of view
Authors: Vogt Jürgen , Lampson Elmar
Published: July 2002

In direct observation, noise and musical tone are polar phenomena. Think of the noise of a falling coin: usually nobody will listen to the quality of this sound but he will immediately think of a falling coin. To perceive a musical tone, inward experience has to be accepted. Although this experience seems to be subjective, a musical tone has an unequivocal and universal quality, whereas noise is diffused and chaotic. Starting from this polarity, an arrangement of the phenomena between noise and tone is deduced. There are two paths: (1) By reduction of the chaotic features of noise, the modes of vibration become simpler. In the end, simple tones are heard or can be ‘‘filtered’’ out by attention. (2) Some or all modes of vibration can lock in the harmonic frequencies as a universal law. The first path is called composition: for a sound which is classified near one of the poles, the significance of the other pole is decreased. The second is called intensification (according to J. W. Goethe’s Farbenlehre): a harmonic sound still has multimode features and sounds characteristic. Simultaneously the tone becomes richer. [Work supported by the Anthroposophische Gesellschaft in Deutschland e.V.]
Feasibility of meeting a limit of 85 dB everywhere inside a power plant
Authors: Scholz Ulrich
Published: July 2002

In recent years the importance of acoustics in the construction of industrial plants has greatly increased. According to many regulations an employee may not be exposed to an 8-h time-weighted average A-weighted sound level of more than 85 dB. The requirement 85 dB at any point is easy to check, even for a nonacoustician. Therefore, a SPL of 85 dB became a standard value in areas with no permanent working places, such as in noisy areas of power plants. Acoustic design in a power station must be handled thoroughly, consistently, and competently. To achieve an optimum solution the plant must be treated as a whole. Knowledge is needed of the processes within power station systems, the components, and their acoustic characteristics, as well as of architectural acoustics, and thermoacoustics. The redevelopment of the cogeneration power station ‘‘Berlin Mitte’’ is used to illustrate the acoustic engineering for a project with stringent indoor requirements. The approach used, noise reductions needed, and noise controls selected are reviewed. The requirement of a level of 85 dB in the near field was achieved. One special highlight was the steam turbine by-pass system, for which the standard design causes 98–108 dB.
Noise control as a revenue enhancer
Authors: Brooks Bennett
Published: July 2002

A small (1.6-MW) power plant was designed to a very strict noise specification. As the various noise sources in plant design iterations were reduced in level, the engine coolers emerged as important noise sources. Noise design requirements dictated that the cooler fan tip speed be significantly reduced. Cooling requirements led to a necessary increase in fan diameter and thus general size of the cooler tube bundles and support structure, at greater acquisition cost. However, the slower fans required smaller electric drive motors. The reduced parasitic load of the smaller motors enabled the plant to export more electric power for revenue. The added investment in quiet fans was recouped in 13 months of operation.
Experimental determination of the effective structure-function parameter for atmospheric turbulence
Authors: Wilson D. K. , Havelock D. I. , Heyd M. , Smith M. J. , Noble J. M. , Auvermann H. J.
Published: July 2002

The effective structure-function parameter for scattering by atmospheric turbulent velocity fluctuations has normally been assumed to be Ceff2=4CV2/c02, where CV2 is the velocity structure-function parameter and c0 the sound speed. However, a new derivation by Ostashev [Waves Random Media 4, 403–428 (1994)], which takes into account the vectorial nature of the wind velocity field, suggests that Ceff2=22CV2/3c02. An experiment was designed to determine the correct value of the coefficient. Sound-pressure amplitude variances were monitored for several discrete frequencies between 380 and 3800 Hz, at distances up to 250 m. Cup and hot-wire anemometers were used to determine CV2. A theory for scattering by inertial-subrange turbulence was then used to calculate the Ceff2 coefficient from the amplitude variance and CV2. Datasets recorded under different atmospheric conditions yielded different relationships between the coefficients and failed to verify either the 4 or 22/3 value. Some possible explanations for this behavior are discussed, including the need for more realistic meteorological modeling.
Yokohama Minato Mirai Hall
Authors: Tachibana Hideki , Kimura Hiroyuki
Published: July 2002

The Yokohama Minato Mirai Hall was planned as a complex cultural facility on the waterfront of Yokohama City and was opened in June 1998. In this building, a large concert hall with 2020 seats (mainly for symphony concerts) and a small concert hall with 400 seats mainly for chamber music are included. For the design and construction of this building, an acoustic design and research group consisting of architects, acousticians, and building engineers was set up and such various acoustic problems as room acoustics, sound insulation between rooms and facades, prevention of structure-borne sound from subway by floating floor construction, and noise reduction of the air-conditioning system were investigated by cooperative work in the group. For the acoustic design of the two halls, computer simulation based on geometrical acoustics and a 1/10 scale model experiment were performed for checking room shape and auralization studies. During and after the construction, acoustic measurements were carried out under various conditions. Before the opening, test concerts were performed with an audience, and acoustic data under occupied conditions were obtained. In this paper, the outline of the design process and the acoustic characteristics of the two halls are introduced.
Acoustical design of the Marienkirche concert hall, Neubrandenburg
Authors: Möller Henrik E. , Lahti Tapio
Published: July 2002

St. Mary’s medieval gothic cathedral in Neubrandenburg, Germany, was ruined at the end of World War II. Two decades ago a decision was made to turn it into a concert hall. The design started in 1996 with the architectural competition, won by Architects Pekka Salminen. The hall will be a combination of old brick walls and mullioned windows, joined with modern glass and concrete. The back wall and the ceiling are made of glass. An audience of 1200 maximum is divided into three blocks: stalls, a balcony, and a tier behind the stage. The initial properties were promising: rectangular, 21 m wide, 18 m high, and with inherent diffusion. The acoustical design was challenged by the restriction of not to touch the old restored side walls. A full-audience reverberation time of 2.0 s was set as a goal. Other objectives were moderate reverberation rise in bass, strong spaciousness and lateral energy. The acoustics were designed with a computer using the Odeon hall design program. Main new elements of acoustical control are a cloud array above the stage, triangular sails near the side wall cornices, and glass reflectors beside the stage. The hall is expected to be inaugurated in autumn 1999.
Acoustic considerations in the redevelopment of the Royal Opera House, London
Authors: Harris Rob
Published: July 2002

The Royal Opera House, Covent Garden is currently closed for a major redevelopment. It is scheduled to re-open in December 1999 with a refurbished and extended main auditorium, a studio theater seating 400, major new ballet studios and facilities for the Royal Ballet, new and refurbished opera and chorus rehearsal rooms, and a completely new backstage, with full wagon facilities and a double height flytower. This paper discusses the acoustic philosophy behind the design and reports the design solutions and the progress on site to date. Matters of particular interest include the approach to the preservation/enhancement of the acoustic of the main house, the dynamics of the ballet studios, the exceptionally large and complex acoustic scenery doors and the acoustic variability incorporated into the studio theater, which is a box-in-box construction.
Acoustic quality in the Theatre ‘‘Palafenice,’’ Venice
Authors: Tronchin Lamberto
Published: July 2002

The burning of the Teatro La Fenice, in Venice, has also been a tragedy for the acoustical community. The Municipality of Venice decided to build a tense-structure (called PalaFenice) on the isle of Tronchetto, as a temporary auditorium for operas and concerts. The use of such a structure provokes many different acoustic problems, quite different from those already known to musicians at La Fenice. In this paper the acoustic quality of the theatre has been analyzed, and compared to the acoustic measurement already performed in the former La Fenice theatre. Binaural measurements have been performed in the hall using the impulse response technique (including absorption of the ceiling), and a dummy head located at different listening positions. According to ISO 3382, many acoustic parameters have been evaluated, like listening level, ITDG, reverberation time, IACC, and others, and their values have been mapped. Also, Ando’s quality maps of preferences, with reference to two different kinds of musical signals, was accomplished from experimental measurements. The measurements pointed out an unsuitable behavior of the structure at low frequency and low reverberation time and intelligibility in the hall. Finally, an hypothesis of the acoustic chamber has been formulated.
Acoustical modifications of the interior design of a 50-ft chapel
Authors: Sémidor Catherine , Merida Emmanuel
Published: July 2002

In order to organize congresses, the University of Sciences in Bordeaux has bought a building with a chapel which will be modified to become both a lecture room and a place for music entertainment with a small orchestra. This paper deals with an interdisciplinary study from the acoustical inventory to the proposition of the new interior design, realized simultaneously by the acoustician team, the architect, and the university. The place, a church, is notable for its high reverberation time. Given this characteristic, a modified MLS software permitting measurements in such halls was tested. The numerical simulation was ajusted from the room-acoustics measured criteria. This reliable model became the base of the study to validate the architectural choices leading to the ‘‘right acoustics’’ for the ‘‘right place.’’ Among several acoustical solutions, the one presenting the more practical application was chosen. The design concept developed for this hall actually permits a variable acoustics to achieve the right level of reverberance for music and good speech clarity for lectures. The results of measurements carried out in the newly opened chapel will be compared with the computed criteria of the last model.