Showing papers in "Acta Acustica United With Acustica in 2006"

A cognitive approach to urban soundscapes : Using verbal data to access everyday life auditory categories

Abstract: The present research on cognitive categories mediates between individual experiences of soundscapes and collective representations shared in language and elaborated as knowledge. This approach focuses on meanings attributed to soundscapes in an attempt to bridge the gap between individual perceptual categories and sociological representations. First, results of several free categorisation experiments are presented, namely the categorical structures elicited using soundscape recordings and the underlying principles of organisation derived from the analysis of verbal comments. People categorised sound samples on the basis of semantic features that integrate perceptual ones. Specifically, soundscapes reflecting human activity were perceived as more pleasant than soundscapes where mechanical sounds were predominant. Second, the linguistic exploration of free-format verbal description of soundscapes indicated that the meanings attributed to sounds act as a determinant for sound quality evaluations. Soundscape evaluations are therefore qualitative first as they are semiotic in nature as grounded in cultural values given to different types of activities. Physical descriptions of sound properties have to be reconsidered as cues pointing to diverse cognitive objects to be identified first rather as the only adequate, exhaustive and objective description of the sound itself. Finally, methodological and theoretical consequences of these findings are drawn, highlighting the need to address not only noise annoyance but rather sound quality of urban environments. To do so, cognitive evaluations must be conducted in the first place to identify relevant city users' categories of soundscapes and then to use physical measurement to characterize corresponding acoustic events.

Soundscape quality in suburban green areas and city parks.

Abstract: According to guidelines proposed in Sweden, at least 80% of the visitors in quiet areas should perceive the sound environment as good This was the starting point for a questionnaire study on "soundscape quality" in four suburban green areas and in four city parks The soundscapes in the suburban areas were completely dominated by sounds from nature (eg, bird song and sounds from water), whereas traffic noise was a main component of the city-park soundscapes Measured equivalent sound levels (from all sources) ranged from 42 to 50 dBA in the suburban green areas, and from 49 to 60 dBA in the city parks (L Aeq,15min ) "Soundscape quality" was assessed by a five-point bipolar category scale Among the respondents, 84-100% in the suburban green areas and 53-65% in the city parks assessed the soundscape as "Good" or "Very good" Thus, all suburban green areas but none of the city parks reached the stipulated goal (at least 80%) The soundcape quality was confirmed by attribute profiling using a set of 12 adjectives Based on the visitor's responses, it is concluded that good soundscape quality can only be achieved if the traffic noise exposure in suburban green areas and city parks during day time is below 50 dBA

The ideal urban soundscape : Investigating the sound quality of french cities

Abstract: A questionnaire study was conducted to investigate the sound quality of urban environments. Seventy-seven participants living in large French cities were questioned about their appraisal of familiar urban soundscapes in a free-response format questionnaire. A psycholinguistic analysis of spontaneous verbal descriptions was conducted to identify semantic categories of environmental sounds and relevant sound quality criteria for urban soundscapes. Our results confirm the influence of semantic features, besides physical ones, on auditory judgments, and further reveal the salience of human sounds.

The quiet rural soundscape and how to characterize it

Abstract: Inhabitants of densely populated cities may benefit from the occasional visit to a restorative environment. The soundscape of this environment may add to the restorative and appealing power of the area. In European directives and policy intentions of many countries, the preservation and management of quiet areas has been subscribed. Nevertheless there is little scientific knowledge on how to characterize such areas and possibly grant quality labels. In this manuscript the quiet rural soundscape is studied within its specific context: non-acoustical environment, use... Several indicators for its characterization are derived from a theoretical point of view. These indicators are tested on usability in a particular case study. This leads us to proposing a multi-criteria assessment of quality labels for the quiet rural soundscape.

Auditory contributions to multisensory product perception

Abstract: The sounds that are elicited when we touch or use many everyday objects typically convey potentially useful information regarding the nature of the stimuli with which we are interacting. Here we review the rapidly-growing literature demonstrating the influence of auditory cues (such as overall sound level and the spectral distribution of the sounds) on multisensory product perception. The results of a number of studies now show that the modulation of the auditory cues elicited by our contact or interaction with different surfaces (such as abrasive sandpapers or even our own skin) and products (including electric toothbrushes, aerosol sprays, food mixers, and cars) can dramatically change the way in which they are perceived, despite the fact that we are often unaware of the influence of such auditory cues on our perception. The auditory cues generated by products can also be modified in order to change people's perception of the quality/efficiency of those products. The principles of sound design have also been used recently to alter people's perception of a variety of foodstuffs. Findings such as these demonstrate the automatic and obligatory nature of multisensory integration, and show how the cues available in one sensory modality can modulate people's perception of stimuli in other sensory modalities (despite the fact that they may not be aware of the importance of such crossmodal influences). We also highlight evidence showing that auditory cues can influence product perception at a more semantic level, as demonstrated by research on signature sounds and emotional product sound design.

Responses to noise in urban parks and in rural quiet areas

Abstract: Nowadays the protection of quiet areas is an issue of increasing importance, as also recognized in the European Directive 2002/49/EC on the environmental noise [1]. Dealing with the demanded protection of quiet areas, it is important to characterize the soundscape of these environments properly, taking into account the multidimensionality of the individual perception which includes the effects of non-acoustic factors on subjective evaluation, such as visual impression and matching the personal expectation of the environment with the actual experience. This paper describes two experimental investigations carried out recently in Italy. The first deals with noise surveys and collection of subjective appraisals of three urban parks in Naples and the second consists of laboratory listening tests where sounds recorded binaurally in countryside parks have been mixed with sounds from some type of sources at different signal-to-noise ratios and played back by headphones to a group of subjects. The results obtained show that the subject's expectation to hear a sound in a specific environment, that is its congruence with the environment where it is heard, influences the corresponding annoyance. In particular, the more the sound is congruent with the expectation of the park, the less is the evoked annoyance and, conversely, the more is its acceptability. Furthermore, the acceptability of the sound increases with decreasing of its level and detectability of non natural sounds.

On a tool for measuring soundscape quality in urban residential areas

Abstract: On a tool for measuring soundscape quality in urban residential areas An attribute-profiling tool, customized for 106 residents’ structured listening walks, was developed for measuring "soundscape quality" in 24 kinds of listening places representing four urban residential areas exposed to road-traffic noise. The tool’s 12 attributes were matched to the soundscape on a scale from 0 to 100%. The attributes were: soothing, pleasant, light, dull, eventful, exciting, stressful, hard intrusive, annoying, noisy and loud. In total, the soundscape quality of 636 unique 30-s soundscapes was measured. For good soundscape quality (pleasant and soothing) to predominate outdoors, the overall sound level of soundscapes had to be below ca. 50 dB LAeq,30s. Indoor soundscapes (closed windows) at exposed sides of buildings were found to be of inferior quality compared to outdoor soundscapes at shielded sides. This was true although the former soundscapes were 14 dB LAeq,30s lower than the latter. A PCA analysis of the 12-attribute profiles of the 24 kinds of listening places shoed that residents actually perceived "signature" of soundscape quality linked to the origin of the soundscapes, whether indoor or outdoors. All soundscapes at shielded sides indoors with closed windows clustered together with the indoor and outdoor soundscapes in the low road-traffic noise exposed residential area. Conversely, at buildings ides with high traffic-noise exposure, all soundscapes, outdoors or indoors with open window, clustered together with their outdoor soundscapes at the shielded d sides. The new attribute-profiling tool is promising because it measures soundscape quality beyond unwanted sounds and mere sound level of predominant noise.

Listening to a City with the soundwalk method

Abstract: Urban sounds are a characteristic part of a city's identity. This paper deals with a method for the evaluation of some characteristics of an urban soundscape. The method is supposed to help urban planners and other town designers to improve the outside acoustics in cities. Besides this, architects pay attention to the way in which transition from one place to another is organised. The method which is supposed to assess urban soundscape is based on the so-called soundwalk, which could be very illustrative for this suggestion. Soundwalks are sound recordings made with a binaural system (SEB) and a DAT recorder, on walks along a route with different urban forms. The different data (commented analyse of each track, recordings, photos, map,...) extracted from the soundwalks are examined in order to gather information about the relationship between the urban characteristics, urban activities and the sound environment. The acoustical images (time versus frequency graphs) of the sound signals can be seen as a representation of the soundscapes. The purpose of this approach is to enable us to evaluate what is pleasant and relevant in an urban sound environment in accordance with activities in the area.

The contribution of sound source characteristics in the assessment of urban soundscapes

Abstract: The aim of this research is to characterize the appraisal of urban soundscapes where sound sources are explicitly recognized. A series of three experiments is conducted in a laboratory where subjects listen to twenty 15-s sound samples representing a sound environment along a classical street in Paris. In these samples, listeners can recognize cars, mopeds, motorbikes, buses, birds and human voices. The first experiment collects ratings of the subjective descriptors "prominence, presence and proximity" of sound sources, the second and third respectively obtain assessments of the overall hedonic judgment and of the loudness of the sound samples. Physical parameters of the different sound sources are extracted from the coded L Aeq curves. Multiple regressions provide a good of the relationship between appraisal and subjective descriptors or objective parameters. They show that, by adding the information about sound source characteristics to the perceived loudness or to the Zwicker's Loudness, the percentage of explained variance increases. To investigate the appraisal of other typical urban soundscapes such as market and park, an on-site experiment using the same procedure is carried out during an urban walk divided into sixteen 90-s sequences. Again the percentage of the explained variance of the hedonic judgement is increased by taking into account the sound source characteristics. The prediction of the scale unpleasantness can even be effective based only on objective characteristics of sound sources such as the number of sources or their time ratio of presence. These results are discussed in terms of sound "events" compared to ambient sound.

The spectrum of glottal flow models

Abstract: A unified description of the most-common glottal-flow models (KLGLOTT88, Rosenberg C, R++, LF) is proposed in the time domain, using a set of five generic glottal-flow parameters: fundamental period, maximum excitation, open quotient, asymmetry coefficient, and return-phase quotient. A unified set of time-domain equations is derived, and their analytical Laplace-transform computation leads to a set of frequency-domain equations. On the basis of this mathematical framework, the spectral properties of the glottal-flow models and their derivatives are studied. It is shown that any glottal-flow model can be described by a combination of low-pass filters, the cut-off frequencies and amplitudes of which can be expressed directly in terms of time-domain parameters. The spectral correlates of time-domain glottal-flow parameters are then explored. It is shown that the maximum excitation corresponds to a gain factor, and that it controls the mid-to-high-frequency spectral slope. A non-null return-phase quotient adds an additional spectral tilt in the high-frequency part of the glottal-flow spectrum. The open quotient and asymmetry coefficient are related to the low-frequency spectral peak, also called the glottal formant. The glottal-formant frequency is mainly controlled by the open quotient, and its amplitude (or bandwidth) by the asymmetry coefficient. As a direct application, it is shown that the amplitude difference between the first two harmonics, commonly assumed to be correlated to the open quotient, is also theoretically dependent on the asymmetry coefficient.

Does timbral brightness scale with frequency and spectral centroid

Abstract: Two models that predict perceived timbral brightness in terms of the centroid of the frequency spectrum were investigated. One model simply uses the centroid of the frequency spectrum, the other divides this same value by the fundamental frequency: the latter scales the centroid of the frequency spectrum with the fundamental frequency. Different single tone and pitch combinations, presented sequentially, were compared. Participants were not-asked to ignore piich differences and intervals of greater than an octave were compared. The results indicate that brightness is much better correlated with frequency spectrum centroid (r = 0.513, p < 0.01) than with the ratio of the centroid of the frequency spectrum to the fundamental frequency (r = 0.030, p = 0.441).

The master hearing Aid : A PC-based platform for algorithm development and evaluation

Abstract: Development and evaluation of algorithms for digital signal processing in hearing aids includes many stages from the first implementation of the algorithmic idea, technical evaluations, subjective evaluations with patients up to field tests, and involves several expert groups, usually physicists, engineers, audiologists and hearing aid acousticians. In order to facilitate this complex process, a common platform for development and evaluation is desirable that covers the whole development process and integrates seamlessly the work of the different expert groups. This paper discusses the possibility of using PC-based hardware for this task. Considering the Master-Hearing-Aid (MHA) developed within the HorTech center of competence on hearing technology as an example, it is shown that the approach of using standardized hardware and software is most promising. The MHA allows for the integration of algorithm development using standard software like Matlab and algorithm evaluation using low-delay real-time processing in combination with user-friendly graphical control interfaces. Performance tests show that real-time processing on modem PC-based hardware is possible even with algorithms written in the Matlab script language, although in this case processing delay is larger and floating point performance is smaller than in algorithms programmed in the C language. For waveform processing, a total delay of 4.35 ms can be reached at less than 5% CPU-load when implemented in C, and a delay of about 94 ms at about 20% CPU-load when implemented as a Matlab script. For spectral FFT-based processing, a total delay of 7.25 ms can be reached at less than 10% CPU-load when implemented in C, and a delay of about 187 ms at about 30% CPU-load when implemented as a Matlab script.

Survey on the acoustical properties of new sustainable materials for noise control

Abstract: According to the definition of sustainability, a product can be considered sustainable if its production enables the resources from which it was made to continue to be available for future generations. A sustainable product can thus be created repeatedly without generating negative environmental effects, without causing waste products or pollution, and without compromising the wellbeing of workers or communities. In the last years many new materials for noise control have been studied and developed as alternatives to the traditional ones (glass or rock wool); these materials are either natural (cotton, cellulose, hemp, wool, clay, etc) or recycled (rubber, plastic, carpet, cork, etc.). Various methodologies have been proposed to evaluate the sustainability of materials and products (LCA, Ecoinvent, Ecoprofiles). The paper presents an updated survey of the acoustical properties of sustainable materials and in particular sound absorption coefficient, airborne and impact sound insulation data, as well as an analysis of the procedures to asses the sustainability of these materials. Euronoise 2006, Tampere, Finland Francesco Asdrubali

Soundscape analysis in a residential area : An evaluation of noise and people's mind

Abstract: In a case study the soundscape of an urban area was investigated in order to show the advantages of a soundscape approach for environmental noise research. The carrying out of the detailed study was motivated by complaints, sleep disturbances and impediments in children's learning in an urban area. Based on narrative interviews the investigation was supposed to provide information about people's perceptions and evaluations of the area as well as attitudes towards specific environmental stimuli. The acoustic constellations which the residents are permanently exposed to were recorded and evaluated. Visual factors which influence sound perception were also taken into account and included into the analysis. Narrative interviews were analyzed systematically with the conceptualization of the Grounded Theory as a sociological method of analysis. By means of the results conclusions about structures and moderating factors in the process of perception could be drawn. With the help of this knowledge gained factors "behind" the dose-response curves can be determined. Furthermore, perception-related decisions can be derived to handle environmental noise problems adequately. All in all, this piece of work shows that the soundscape approach with its multidisciplinary groundings and perspectives can help to overcome sectoral barriers.

A tutorial on scattering and diffusion coefficients for room acoustic surfaces

Abstract: Institute of Technical Acoustics, Technical University Aachen, 52056 Aachen, GermanySummaryThere is a need to be able to quantify how sound is re”ected from a surface, in terms of how it is spatiallydispersed. In recent years, di usion and scattering coe cients have been developed to enable room acousticpredictionmodelstobemoreaccurate,anddesignerstoevaluatetheworthofdi usingsurfaces.Twocoe cientshave been, or are about to be, enshrined in standards. With two coe cients being standardised, there is greatpotential for confusion. This paper is intended to bring together authors from di erent areas to explain where thecoe cients should and should not be applied. In addition, this tutorial paper will revisit the rationale behind thecoe cients and contrast the coe cient de“nitions and performance.

Qualitative judgements of urban soundscapes : Questionning questionnaires and semantic scales

Abstract: The present work aims at a qualitative analysis of various soundscapes in two French cities in order to evaluate and potentially improve urban development. The method employs an analysis of open-ended questions and of verbal comments and judgments on a semantic differential grid. On-site experiments were carried out in various urban locations of two French cities, such as main thoroughfares, pedestrian districts, playgrounds and market squares. Differential patterns were clearly seen from a histogram analysis of the differential grid, which points to the limits of an average calculation of the semantic scale. A psycholinguistic analysis of the verbal comments was carried out to explicate the heterogeneous judgements across people about temporal, spatial and activity appraisals that the quantitative data obscure. Such an analysis allowed us to differentiate two cognitive modes for representing urban soundscapes: (i) a "descriptive listening" mode which refers to the identification of acoustic sources or events; and (ii) a "holistic hearing" mode which refers to the soundscape as a whole, without semantic processing of any specific sources. Since the same physical phenomenon may be interpreted by two distinct cognitive representations, the results highlight the need for employing differential scales with a semantic analysis to improve qualitative judgement and to further elaborate new semantic as well as physical indicators based on community noise measurements.

Psychoacoustics and its Benefit for the Soundscape Approach

Abstract: Summary The increase of complaints about environmental noise shows the unchanged necessity of researching this subject. By only relying on sound pressure levels averaged over long time periods and by suppressing all aspects of quality, the specific acoustic properties of environmental noise situations cannot be identified. Because annoyance caused by environmental noise has a broader linkage with various acoustical properties such as frequency spectrum, duration, impulsive, tonal and low-frequency components, etc. than only with SPL [1]. In many cases these acoustical properties a ect the quality of life. The human cognitive signal processing pays attention to further factors than only to the averaged intensity of the acoustical stimulus. Therefore, it appears inevitable to use further hearing-related parameters to improve the description and evaluation of environmental noise. A first step regarding the adequate description of environmental noise would be the extended application of existing measurement tools, as for example level meter with variable integration time and third octave analyzer, which o er valuable clues to disturbing patterns. Moreover, the use of psychoacoustics will allow the improved capturing of soundscape qualities.

Review of the Impact Ball in Evaluating Floor Impact Sound

Abstract: The purpose of this study was to review the use of a new standard impactor, the impact ball, in evaluating heavyweight impact sounds in multi-story reinforced concrete residential buildings. Physical properties such as impedance and force of the impact sources, including the impact ball and human activity, were measured. In particular, noise from the impact ball was analyzed and the relationships between sound levels and subjective responses were investigated. The results showed that the noise from the impact ball is similar to the noise of children running and jumping, and that subjective responses to the noise correlate well with Zwicker's Loudness model and the newly defined floor impact sound level (L i,F max,AW). It was also found that the noise level of the impact ball is slightly higher than that of the bang machine, although the impact ball has a lower impact force. In addition, when the noise from the impact ball was evaluated under both laboratory and in-situ conditions, the allowable sound level was found to be 54 dB (L i,F max,AW).

Micro-perforated structures as sound absorbers : A review and outlook

Abstract: Sound absorbers employing micro-perforated panels or foils have long been used as attractive measures in room acoustics. So far, however, all applications have tried to activate the holes in such structures as fluid mass elements in a Helmholtz-resonator arrangement in front of a rigid backing with an air cushion in between acting as a spring element. With a slightly modified realization of the geometry of the micro-holes it now becomes possible to use micro-perforated surface structures as stand-alone, bilaterally active acoustic elements with some obvious practical benefits for their users: the new absorbers function with a minimum of space, material and costs required. Maa's ingenious idea of a sound absorber, which can do without any damping material incorporated in it, has thus found a very useful extension "with immense possibilities ahead" as he put it when reading the manuscript.

Sound insulation of double panels : Comparison of existing prediction models. Commentary and Author's reply

Abstract: Numerous qualitative comparisons between existing prediction models for the sound insulation of double panels have been presented in the literature but quantitative comparison between models is still lacking. It is important to have impartial evidence of the applicability and accuracy of the prediction models before any of them can be applied for real double wall structures. The aim of this study was to present a qualitative and quantitative comparison of the existing double wall prediction models. Seventeen models were implemented. Quantitative comparison between models was made in four categories: without studs and cavity absorbent, without studs and with absorbent, rigid studs with absorbent, and flexible studs with absorbent. The quantitative comparison of the models was made against measurement data containing altogether 52 laboratory tests for double walls. The average prediction errors for individual frequencies were as high as 20 dB (R w : 15 dB) for most of the models, while it was less than 10dB (R w : 5dB) for the best models. None of the models was sufficiently accurate in all four categories. There is an obvious need to develop a new model, which can be reliably applied to arbitrary double and multilayer walls. In the present situation, the most accurate model should be selected according to the type of the double wall.

Voice instabilities due to source-tract interactions

Abstract: Interactions of voice source and vocal tract resonances are of particular interest with respect to register transitions and bioacoustics. There is experimental evidence that singing into a tube generates nonlinear phenomena around matching frequencies of the pitch and the first formant. In the present study, we analyze a simplified two-mass model coupled to a straight tube. The essential parameters of the systems are varied systematically to localize instability regions in parameter space. The resulting bifurcation diagrams reveal subharmonic vibrations and deterministic chaos if the pitch and the first formant coincide. The computer simulations closely resemble published experimental observations. Furthermore, we demonstrate the role of coupling strength as the cause of instability. Small tube cross sectional areas and sufficiently large pressures are responsible for additional instability regions around second pitch harmonic and formant resonance. The results indicate that under certain circumstances source-tract interactions induce quite complex voice instabilities, even for symmetric vocal folds. These include frequency jumps, subharmonic regimes and chaos. The possible relevance for the soprano whistle voice and animal vocalization is discussed.

Edge-diffraction impulse responses near specular-zone and shadow-zone boundaries

Abstract: Many methods for the computation of edge-diffraction impulse responses are based on the Biot-Tolstoy solution, an explicit, continuous-time expression for diffraction by an infinite wedge. This expression contains two singularities at the onset of the impulse response: one which is present for all source-receiver combinations, and a second which occurs only when a receiver moves across a specular-zone or shadow-zone boundary, i.e. a boundary where a geometrical-acoustics component has a discontinuity. For the calculation of discrete-time impulse responses, such a continuous-time analytical expression must be numerically integrated, and the singularities demand special attention. Svensson et al. [U. P. Svensson et al., J. Acoust. Soc. Am. 106, 2331-2344 (1999)] presented an analytic, secondary-source model of edge diffraction based on the Biot-Tolstoy expression in which the first singularity was eliminated by reformulating the expression as an integral along the edge. In this paper, analytical approximations for the model presented by Svensson et al. are described which address the second type of singularity and thus allow for accurate numerical computations for receivers at or near zone boundaries. Implementation details are also provided, along with example calculations.

The dynamics of Tibetan singing bowls

Abstract: Tibetan bowls have been traditionally used for ceremonial and meditation purposes, but are also increasingly being used in contemporary music-making. They are handcrafted using alloys of several metals and produce different tones, depending on the alloy composition, their shape, size and weight. Most important is the sound-producing technique used - either impacting or rubbing, or both simultaneously - as well as the excitation location, the hardness and friction characteristics of the exciting stick (called puja). Recently, researchers became interested in the physical modelling of singing bowls, using waveguide synthesis techniques for performing numerical simulations. Their efforts aimed particularly at achieving real-time synthesis and, as a consequence, several aspects of the physics of these instruments do not appear to be clarified in the published numerical formulations and results. In the present paper, we extend to axi-symmetrical shells - subjected to impact and friction-induced excitations - our modal techniques of physical modelling, which were already used in previous papers concerning plucked and bowed strings as well as impacted and bowed bars. We start by an experimental modal identification of three different Tibetan bowls, and then develop a modelling approach for these systems. Extensive nonlinear numerical simulations were performed, for both impacted and rubbed bowls, which in particular highlight important aspects concerning the spatial patterns of the friction-induced bowl vibrations. Our results are in good agreement with preliminary qualitative experiments.

Bubble cluster dynamics in acoustic cavitation

Abstract: The dynamics of acoustic cavitation bubbles in clusters is investigated. Using high-speed photographic recordings, subharmonic oscillations of clusters near objects in standing wave fields are documented. A cluster model is used to investigate the parameter dependence of period-doubled dynamics of clusters. It is found that for increased bubble population, clusters of larger bubbles (some tens of μm) tend to oscillate subharmonically, while the opposite is true for clusters of smaller bubbles (below 15 μm). In polydisperse clusters, synchronization of period and collapse phase is found.

Numerical modelling of effect of tonsillectomy on production of czech vowels

Abstract: Aim of the study is to numerically examine the effect of tonsillectomy on production of Czech vowels. Similar experimental studies on living subjects are not easily realisable. The finite element (FE) models of the acoustic spaces corresponding to the human vocal tracts and acoustic space around the human head are used in numerical simulations of-phonation. Models for Czech vowels /a/, le/, /i/, /o/ and /u/ are analyzed. The acoustic resonant characteristics of the FE models are studied using modal and transient analyses (excitation by a short pulse). The production of vowels is simulated in time domain using transient analysis of the FE models excited by Liljencrants-Fant's (LF) glottal signal model. Calculated results show that tonsillectomy causes frequency shifts of some formant frequencies mostly down to lower frequencies. Biggest shifts were obtained for 3rd and 4th formants for vowel /o/ ∼300Hz down to lower frequencies, for 3rd (∼450 Hz) and 4th (∼150 Hz) formants for vowel /u/ and for 4th (∼200 Hz) formant of vowel le/ down too. The frequency shifts of the formants are significantly dependent on position and size of the tonsils.

Natural and urban soundscapes : The need for a multi-disciplinary approach

Abstract: Characterizing soundscapes requires a broad variety of approaches (ecological, sociological, phenomenological) in a soundscape continuum from completely natural to highly urban environments. There is an urgent need for the use of innovative designs which integrate the different levels of current analyses (qualitative and quantitative; individual and aggregate levels). The criteria (beyond sound level) of a "good" soundscape addresses the questions: What is a "sensitive" soundscape? What are soundscape requirements for a "resort area?" or "natural quiet?" that should be protected. Answers to these questions are central to the origin of the soundscape idea. Presented here is a simple soundscape model of the interactions between natural and man-made elements of soundscapes. Soundscape elements are characterized. Lists are presented of the disciplines involved in understand soundscapes and the main'quantitative metrics that can be measured.

Time-domain modeling of the acoustic impedance of porous surfaces

Abstract: A time-domain boundary condition (TDBC) for acoustic reflections from a rigid-frame porous material is derived. The TDBC is the time-domain counterpart of the familiar, linear, frequency-dependent surface impedance for locally reacting surfaces. Although the TDBC is developed from a rather simple, two-parameter phenomenological model, it is shown to apply to a broad range of frequencies and to agree closely with predictions from more sophisticated models that do not have readily derivable time-domain formulas. The TDBC gives the pressure as the sum of two terms involving the particle velocity normal to the surface of the material: one term is directly proportional to the particle velocity at the present time, whereas the other involves a convolution of the particle velocity with a slowly decaying response function. Numerical implementation of the TDBC is discussed and illustrated with example finite-difference, time-domain calculations involving propagation over a porous ground surface.

Case studies on structural-acoustic optimization of a finite beam

Abstract: This paper presents a case study on structural-acoustic optimization. It demonstrates the potential of the application of normal modes in external acoustics for optimization of radiating structures. Herein, a radiating beam is investigated in half space (baffled beam) and in free space. Optimization is run for different cases of excitation and bearing conditions. The radiated sound power level is minimized in a frequency range of approximately eight modes of the structure. The frequency range under consideration starts above the lowest elastic mode. Density, thickness and Young's modulus account for the optimization variables. A number of interesting results are reported. Substantial improvements may be achieved in cases where the a point force is applied. In cases of distributed load, gains are much more moderate. Density and thickness seem to be well suited for these optimization purposes whereas the Young's modulus seems to influence the objective function much less. Essentially, the results of optimization appear very sensitive with respect modification of the load's location but robust with respect to bearing conditions.

Efficiency of noise protections in urban areas : Predictions and scale model measurements

Abstract: This research work aims at creating quiet areas in cities using low height complex shape noise reduction devices. For aesthetic and security aspects, such protectors will not exceed a size of 1 mx 1 m in a vertical section. Numerical simulations of their acoustical performance were achieved using a 2D Boundary Element Method (BEM) code developed at CSTB named MICADO. The results show that the effectiveness of such protections is very significant: the noise reduction due to their use may be as high as 6 to 10 dB(A) in the area of interest. Scale model measurements have been carried out at a scale of one to ten; they also confirm this significant effectiveness. There is good agreement between 2D theoretical results and 3D scale model measurements. Such low height protections seem to be particularly effective at low frequencies.

Comparison of the effects of verbal versus visual information about sound sources on the perception of environmental sounds

Abstract: We perceive our environment by integrating multi-modal information. Although researchers have attempted to interpret sound perception solely through hearing, few attempts have been made using multi-modal information to understand our perception of environmental sounds. In this study, we conducted three experiments in which the sound stimuli were presented alone, with corresponding verbal information, or with corresponding visual information. In order to investigate the difference in the perception attributable to the verbal and visual information, analysis of variance was applied to the factor scores of each stimulus. Our analyses revealed that the effects of additional information on factor scores were different for verbal and visual information, except in the case of brightness. We suggest that the image intrinsic to a sound sources, evoked by verbal and visual information, affects the evaluation of sounds. Furthermore, moving pictures (visual information) contain a variety of information, whereas verbal information gives only determinative information. When this discrepancy produces appreciable differences between verbal and visual information, the changes in the factor scores can be rationally explained. Hence, we consider both the visibility and movement of the sound source to be important factors in our perception of environmental sounds.