An analysis of the effects of structural parameter variations on the auditory perception of environmental noises transmitted through a simulated window

The present paper concerns the influence of the independent variation of some structural parameters on the auditory perception of environmental noises transmitted through a window. The pane of glass in its frame was modelled as a thin baffled plate with viscoelastic boundary conditions; transmitted noises were then synthesized by convolving a binaurally recorded environmental noise to different calculated impulse responses of the plate involving so many different values of the structural parameters (structural damping factor and mounting conditions). Stimuli were pairwise submitted to a jury of subjects who were asked to give dissimilarity and preference judgments. Analysis first allowed to identify the relevant auditory attributes that were likely used by the subjects in their differentiation task, and also focused on drawing up a preference ranking of the transmitted noises in order to provide recommendations for window structural modifications that could improve acoustic comfort in inner spaces. On this point, depending on the structural parameter, recommendations appear to be more or less consensual in relation to the outdoor sound context.     

Using response surface methodology for optimizing deposited partially stabilized zirconia in plasma spraying

This paper presents the application of the surface response methodology and fractional factorial experiment in developing a robust partially stabilized zirconia (PSZ) coating in plasma spraying processes. In this study, a two-step experimental design with a nonlinear regression model is proposed. After conducting a series of initial experiments in a controlled environment, significant factors for plasma spraying processes are selected to construct an appropriate response surface model for developing a robust performance for plasma spraying processes.The experimental results show that using a quadric response surface model with the proposed two-step design strategy is a simple, effective and efficient approach. In the optimized model, several response plots were generated to examine parameter effects on the profile hardness. Optimization of the PSZ performances in a plasma spray process has been performed.     

Dynamics of the tuning process between singers

We present a dynamical model describing a predictable human behavior like the tuning process between singers. The purpose, inspired in physiological and behavioral grounds of human beings, is sensitive to all Fourier spectrum of each sound emitted and it contemplates an asymmetric coupling between individuals. We have recorded several tuning exercises and we have confronted the experimental evidence with the results of the model finding a very well agreement between calculated and experimental sonograms.Received: 28 August 2004, Published online: 5 November 2004PACS: 43.66.Ba Models and theories of auditory processes - 43.75.Cd Music perception and cognition - 43.75.Rs Singing     

Thermo-acoustic performance of full engine encapsulations – A numerical,experimental and psychoacoustic study

This paper presents the development and investigation of a thermo-acoustic encapsulation for a diesel engine by means of a combined approach of thermo-acoustic recordings, numerical simulations and psychoacoustic evaluation. The encapsulation is positioned in close proximity to the engine and completely surrounds the entire engine block. Experimental tests are performed with the help of an acoustic engine test bench, where the surface of the engine is observed by infrared cameras and the sound is monitored by a microphone-array. Thermal and acoustic measurements of the engine without an encapsulation are recorded and used as reference data for simulations to evaluate and improve the functionality of different design concepts of the encapsulation in comparison to the same engine without encapsulation. The received experimental results are also used to select proper materials as well as to design the heat insulating and sound absorbing encapsulation. Based on the experimental investigations, some weak points of the first prototype are identified. These experimental findings, as well as numerical simulations of the sound radiation, are used as a basis for further design improvements to the encapsulation. The new design that is developed shows a significant improvement in the insulation of the car engine, both thermally and acoustically. In the last step, the perception of the engine sounds are evaluated by measuring changes in the perceived loudness and sound preference of the engine with and without encapsulation by human participants. This allows for a more objective evaluation of the acoustic behavior of the developed engine encapsulation.     

Subjective evaluations of sound radiated by impacted plates, using the design of experiments method

This study combines physical and subjective approaches to evaluate the sound quality of impacted plates. A numerical model, based on the Hertz law of contact, has been used to determine the sound pressure level at any point in space resulting from an impact. Sounds synthesized using this model and those from experiments can then be exploited in a physical analysis and/or a subjective analysis of the effects associated with variations in parameters. Here the influence of certain physical parameters on the sound perception of impacted plates is evaluated through a design of experiments method and a subjective test of preference. The subjective test is based on an estimate of preference between two pairs of synthetic sounds by varying several structural parameters at the same time. This differs from other studies that vary only one parameter at a time and fix the other parameters.     

Transient sound radiated by spheres undergoing an elastic collision

An experimental and theoretical analysis of the sound field radiated by the collision of two elastic spheres is presented. The sound pressure measured at any point in space is the proper sum in time of the sound radiated independently by each sphere. It is shown that the combination of classical Hertzian impact theory and acoustical theory is sufficient to define the pressure time waveforms as measured in the experiments.     

Vibrations’ influence on Dieselness perception

Up to now, different studies dealing with vibrations’ influence on acoustics have been, in most cases, realized on global annoyance. In our case, the present study examines the vibrations’ influence on the auditory perception of Diesel character (called Dieselness in this article) of a vehicle. In addition, cultural experience is evaluated by testing two groups of Diesel owners from two European countries (respectively France and Germany). During the experiment, each population was exposed to sound only, and sound and vibrations simultaneously. This perceptual test was realized on a vibration bench (driver seat and steering wheel) with headphones. Three kinds of vehicules and six different driving situations have been tested. Results reveal no differences between French and German. Nevertheless, the adding of vibrations influences the Dieselness evaluation. The participants give slightly higher scores (more Diesel) or equal (as Diesel) with vibrations than without. However, this vibration effect is slightly dependent on the type of vehicles and on the driving situations and it appears less important for German people. In addition, for each group of participants, the other factors vehicle and driving situation have an effect on Dieselness assessment. The effect of vehicle allows to show that 3 cylinders car is significantly different from 4 cylinders and 6 cylinders cars. Finally, the interaction between driving situation and vehicle shows the strongest effect on Dieselness evaluation, among all interactions tested. The vehicle effect is dependent on the driving situation. All results and conclusions have to be taken with care in order not to generalize for all similar classification cars.     

Comparative measurements of loudspeakers in a listening situation

Comparison of loudspeakers is a major concern during design or product selection. There are several standards for the measurement of loudspeaker characteristics, but none of them provides hints for a rigorous comparison between devices. In this study, different ways of evaluating acoustical dissimilarity between loudspeakers were compared. Several methods of signal analysis were used, and for each method a metric evaluating the dissimilarity between two signals was defined. The correlation between the different dissimilarity evaluations over a significant panel of loudspeakers led to identified classes of measurements. A specific aspect of this work is that measurements were performed in a standard listening environment, rather than in an anechoic or reverberant one. It allowed the use of the recorded signals for a simple listening test, providing a perceptual metric which was compared to the acoustical ones. It also allowed the introduction of auditory models in the computation of some acoustical metrics, so defining a new class of measurements which gave results close to the perceptual ones.     

DISSIMILARITY JUDGMENTS IN RELATION TO TEMPORAL AND SPATIAL FACTORS FOR THE SOUND FIELD IN AN EXISTING HALL

In relation to the temporal and spatial factors of sound fields, dissimilarity judgments for different source locations on a stage were performed. This study is based on the model of the auditory-brain system, which consists of the autocorrelation and crosscorrelation mechanisms for sound signals arriving at two ears and the specialization of human cerebral hemispheres. There are three temporal factors (τ₁,φ₁ and τ_e) extracted from the autocorrelation function and four spatial factors (LL,IACC,τ_IACC and W_IACC) from the interaural crosscorrelation function of binaural signals. In addition to these temporal and spatial factors, the orthogonal factors of the subjective preference for sound field (Δt₁ and T_sub) were taken into account. The psychological distance between sound fields of different source locations on the stage were calculated by using these temporal, spatial and orthogonal factors of sound fields. Using these distances and their linear combination, dissimilarity can be calculated. Results of multivariable analysis show that the calculated scale values of dissimilarity agree well with the measured scale values.     

Year-to-year variability of the long-range propagation conditions in the Norwegian Sea

On the basis of the experimental data on the sound field formation in the Norwegian Sea, the year-to-year variability of the propagation conditions is estimated. A comparative analysis is performed for the data obtained from two long-range-propagation experiments with explosion-generated signals. The experiments were carried out in summertime (August) on a path crossing the central deep-water part of the Norwegian Sea and were separated in time by a period of four years. Noticeable changes are found to occur in the sound speed fields between the two experiments. These changes are related to a change in the distance between the cores of cold waters (observed in the region of the Norwegian Basin) and warm waters (observed in the region of the Lofoten Basin). According to calculations, the observed changes in the sound speed structure can lead to considerable changes in the propagation anomaly and in the range dependence of the sound field decay. In spite of the noticeable difference in the propagation conditions, the experimental coefficients of low-frequency attenuation differ little for the two experiments.     

ACOUSTIC POWER SUPPRESSION OF A PANEL STRUCTURE USING H∞OUTPUT FEEDBACK CONTROL

This paper presents a robust control system design for suppressing the radiated acoustic power emitted from a vibrating planar structure, and spillover effect caused by neglected high-frequency modes. A state-space model of a simply supported panel structure is derived and an output equation is formed based on the one-dimensional PVDF film sensors. An output feedback H_∞control is designed by introducing a multiplicative perturbation which represents unmodelled high-frequency dynamics in the control system. The simulation and experimental results demonstrated significant decrease in sound radiation for the considered structural power modes in control.     

Dissimilarity and the Classification of Female Singing Voices: A Preliminary Study

Traditionally, timbre has been defined as that perceptual attribute that differentiates two sounds when pitch and loudness are equal and thus is a measure of dissimilarity. By such a definition, each voice possesses a set of timbres, and the identity of any voice or voice category across different pitch-loudness-vowel combinations must be due to an abstraction of the pattern of timbre transformation. Using stimuli produced across the singing range by singers from different voice categories, this study sought to examine how timbre and pitch interact in the perception of dissimilarity. This study also investigated whether listener experience affects the perception of timbre as a function of pitch. The resulting multidimensional scaling (MDS) representations showed that for all stimuli and listeners, dimension 1 correlated with pitch, whereas dimension 2 correlated with spectral centroid and separated vocal stimuli into the categories mezzo-soprano and soprano. Dimension 3 appeared highly idiosyncratic depending on the nature of the stimuli and on the experience of the listener. Inexperienced listeners appeared to rely more heavily on pitch in making dissimilarity judgments than did experienced listeners. The resulting MDS representations of dissimilarity across pitch provide a glimpse of the timbre transformation of voice categories across pitch.     

SOUND TRANSMISSION THROUGH ELASTOMERIC BULB SEALS

The sound barrier performance of elastomeric vehicle weather seals was investigated. Experiments were performed on a single bulb seal specimen using a reverberation room method. The seal wall velocity was measured using a laser Doppler vibrometer. The sound pressure near the velocity measurement location was measured simultaneously, which allowed the sound intensity on both sides of the seal and the sound transmission loss to be determined. The vibration response and the sound transmission loss of the bulb seal were then computed using finite element analysis. Acoustic-structure interactions were considered for a partially coherent spatially distributed pressure excitation. The experimental data obtained using the reverberation room method allowed the validation of the numerical models. The resonance frequency due to the mass-air-mass mode of vibration was accurately predicted. The model was then used to numerically investigate the influence of various design parameters. It was found that the elastic modulus significantly affects the bulb seal resonance frequency, and that the loss factor of the material has major effects on the sound transmission loss around resonance.     

A sound quality-based investigation of the HVAC system noise of an automobile model

Using methods and techniques of sound quality engineering, the noise of the heating, ventilation and air-conditioning system (HVAC) of an automobile model was studied. Such noise has a great influence on vehicle acoustical comfort and on overall quality perception of a vehicle. The study was divided into two steps. The first step aimed to identify the most significant attributes that contribute to the perception of similarity or dissimilarity of this kind of noise, using the paired comparison technique and correlation of the results with psychoacoustic models. Loudness, spectral composition and tonality, represented by the psychoacoustic models of loudness, sharpness, tone-to-noise ratio and prominence were found to be the most important dimensions for the perception of similarity and dissimilarity of HVAC-noise.In the second step of the study a model to predict subjective response to HVAC sounds using the semantic differential technique was developed. In particular the perception of annoyance was studied and it is shown that the annoyance caused by the HVAC noise can be satisfactorily described by Zwicker’s stationary loudness model, provided that the HVAC noises do not present tonal components. The loudness model also predicts scores on a quiet/loud scale. Both results confirm the power of the loudness dimension and its model introduced by Zwicker for the overall quality of stationary broadband sounds without slow fluctuations or tonal components. From the annoyance model developed in this study a maximum acceptable loudness level for HVAC-systems can be determined.     

Directional perception of distributed sound sources

The perception of spatially distributed sound sources was investigated by conducting two listening experiments in anechoic conditions with 13 loudspeakers evenly distributed in the frontal horizontal plane emitting incoherent noise signals. In the first experiment, widely distributed sound sources with gaps in their distribution emitted pink noise. The results indicated that the exact loudspeaker distribution could not be perceived accurately and that the width of the distribution was perceived to be narrower than it was in reality. Up to three spatially distributed loudspeakers that were simultaneously emitting sound could be individually perceived. In addition, the number of loudspeakers that were indicated as emitting sound was smaller than the actual number. In the second experiment, a reference with 13 loudspeakers and test cases with fewer loudspeakers were presented and their perceived spatial difference was rated. The effect of the noise bandwidth was of particular interest. Noise with different bandwidths centered around 500 and 4000 Hz was used. The results indicated that when the number of loudspeakers was increased from four to seven, the perceived auditory event was very similar to that perceived with 13 loudspeakers at all bandwidths. The perceived differences were larger in wideband noise than in narrow-band noise.     

Evidence of self-affine multiplicity fluctuation of target residues in 84Kr-AgBr interactions at 1.7 AGeV

Self-afline multiplicity scaling is investigated in the framework of a two-dimensional factorial mo-ment methodology using the concept of the Hurst exponent (H). Analyzing the experimental data of target evaporated fragments emitted in84Kr-AgBr interactions at 1.7 AGeV revealed that the best power law behav-ior is exhibited for H = 0.3 indicating a self-affine multiplicity fluctuation pattern. A signal of multifractality is also observed from knowledge of the anomalous fractal dimension dq extracted from the intermittency exponent aq of the anisotropic phase space scenario.     

Self-affine multiplicity fluctuation of target residues in relativistic nuclear collisions at a few GeV to a few hundred GeV

Self-affine multiplicity scaling is investigated in the framework of two-dimensional factorial moment methodology using the concept of the Hurst exponent (H). Our investigation on experimental data of the target-evaporated slow particles emitted in ³²S-AgBr interactions at 200 AGeV and ²⁸Si-AgBr interactions at 14.5 AGeV reveals that a better power law behavior is exhibited in self-affine analysis than self-similar analysis. This work shows a clear evidence of self-affine target fragmentation. Received: 22 October 2001 / Accepted: 6 March 2002     

Modeling refraction characteristics of silicon nitride film deposited in a SiH/sub 4/-NH/sub 3/-N/sub 2/ plasma using neural network

Silicon nitride has been deposited using plasma-enhanced chemical deposition (PECVD) equipment. The PECVD process was characterized by conducting a 2/sup 6-1/ fractional factorial experiment on six experimental factors, including substrate temperature, pressure, radio frequency (RF) power, ammonia NH/sub 3/, silane SiH/sub 4/, and nitrogen N/sub 2/ flow rates. Refractive characteristics of the deposited film were examined by modeling the refractive index as a function of experimental factors. A helium-neon laser with a wavelength 6328 /spl Aring/ was used to measure the refractive index. To evaluate the appropriateness of the model, the network trained with 32 experiments was then tested with 12 experiments not pertaining to the training data. Several learning factors involved in training neural networks were optimized and an accurate prediction model with the root mean-squared error of 0.018 was achieved. Compared to statistical regression model, the neural network model demonstrated an improvement of more than 65%. Using various three-dimensional plots, underlying deposition mechanisms were qualitatively estimated. For the limited experimental ranges, the index increased with increasing SiH/sub 4/ flow rate. With an increase in either NH/sub 3/ or N/sub 2/, meanwhile, the index decreased consistently. The index also increased with increasing substrate temperature or pressure. The effects of the temperature were very complex as it interacted with other factors.     

Estimation of multiple sound source directions using artificial robot ears

Estimating the direction of a sound source is an important technique used in various engineering fields, including intelligent robots and surveillance systems. In a household where a user’s voice and noises emitted from electric appliances originate from arbitrary directions in 3-D space, robots need to recognize the directions of multiple sound sources in order to effectively interact with the user.This paper proposes an ear-based estimation (localization) system using two artificial robot ears, each consisting of a spiral-shaped pinna and two microphones, for application in humanoid robots. Four microphones are asymmetrically placed on the left and right sides of the head. The proposed localization algorithm is based on a spatially mapped generalized cross-correlation function which is transformed from the time domain to the space domain by using a measured inter-channel time difference map. For validation of the proposed localization method, two experiments (single- and multiple-source cases) were conducted using male speech. In the case of a single source, with the exception of laterally biased sources, the localization was achieved with an error of less than 10°. In a multiple-source environment, one source was fixed at the front side and the other source changed its direction; from the experimental results, the error rates on the localization of the fixed and varying sources are 0% and 36.9% respectively within an error bound of 15°.