Evaluations of output from room acoustic computer modeling and auralization due to different sound source directionalities

Evaluations of the predictions and auralizations from the room acoustic modeling program, ODEON, have been run using three directional source types with the same sound power: (a) an omni-directional source; (b) three sources with realistically-directional characteristics based on measurements from real instruments (grand piano, violin, and singing voice); and (c) an artificial, extremely directional beaming source. Objective analyses have been run for nine source/receiver combinations in a simple hall on three acoustic parameters: relative sound pressure level (SPL), reverberation time (T30), and clarity index (C80). Auralizations were subsequently created for two source/receiver combinations and used in subjective testing with 28 subjects. Results show that, objectively, differences in SPL were negligible for the majority of cases. Some differences in T30 and C80 were found between the omni-directional and realistically-directional sources; however, subjects did not perceive any corresponding differences when comparing the auralizations, possibly due to the limited directional octave band data available. Subjects did significantly differentiate between auralizations from the omni-directional source and the extreme beaming source. Subjective results from comparing these two sources in terms of reverberation, clarity and realism were generally consistent with objective data, although source/receiver combination and musical track had some influence on the outcomes.     

Objective and subjective evaluations of twenty-three opera houses in Europe, Japan, and the Americas

The room acoustical parameters, reverberation time RT, early decay time EDT, clarity factor C80, bass ratio BR, strength G, interaural cross-correlation coefficient IACC, and initial-time-delay gap ITDG [definitions in Hidaka et al., J. Acoust. Soc. Am. 107, 340-354 (2000) and Beranek, Concert and Opera Halls: How They Sound (Acoustical Society of America, New York, 1996)], were measured in 23 major opera houses under unoccupied conditions in 11 countries: Argentina, Austria, Czech, France, England, Germany, Hungary, Italy, Japan, The Netherlands, and the USA. Questionnaires containing rating scales on the acoustical quality of 24 opera houses were mailed to 67 conductors, 22 of whom responded. The objective measurements were analyzed for reliability and orthogonality, and were related to the subjective responses. Presented are (a) the rankings of 21 opera houses each rated by at least 6 conductors for acoustical quality as heard by them both in the audience areas and in the pit; (b) relations between objective room acoustical parameters and subjective ratings; (c) findings of the most important of the parameters for determining acoustical quality: RT (or EDT), G(M), ITDG, [1 - IACC(E3)], texture (appearance of reflectrograms in the first 80-100 ms after arrival of the direct sound), a lower limiting value for BR, and major concern for diffusion and avoidance of destructive characteristics (noise, vibration, echoes, focusing, etc.); (d) the differences between average audience levels with and without enclosed stage sets; and (e) the differences between average levels in audience areas for sounds from the stage and from the pit.     

Simultaneous all-optical multi-channel RZ and CSRZ to NRZ format conversion

We propose and demonstrate multi-channel all-optical return-to-zero (RZ) and carrier-suppressed RZ (CSRZ) to non-return-to-zero (NRZ) format conversions using a same fiber delay-interferometer (DI). The conversions are based on simultaneous constructive interference induced by the periodical comb-like filtering characteristic of the DI. By using a DI with free spectral range of 40 GHz, 8 channel RZ and CSRZ signals at 20 Gb/s can be converted to corresponding NRZ signals at the same time. Furthermore, a duplicate output can be obtained for multi-channel CSRZ input. Bit error ratio measurements show 4 and 3.5 dB penalties for the proposed multi-channel RZ and CSRZ to NRZ conversions respectively. Further transmission for the converted NRZ signals verifies the good performance of the proposed all-passive multi-channel format converter. The potential of multi-channel RZ signals with mixed duty-cycle to NRZ conversions is also investigated.     

Application of multi-channel spectral analysis to identify the source of a noise amplitude modulation in a diesel engine operating at idle

We are interested in the low frequency amplitude modulation of the noise generated by an engine operating at idle. This phenomenon, perceived inside the car, is particularly annoying. Modulated vibrations are transmitted to the frame mainly by one of the three engine mounts. The combustion is the first potential source to be inspected, but pragmatic observations on consecutive measurements show that it is not the cause of the amplitude modulation. Spectral analysis tools are applied on multi-channel measurements to identify the source of the phenomenon. A sensor is placed on each potential noise and vibration source. A virtual source analysis show that several uncorrelated sources are contributing to the operating response, particularly on frequencies for which a high amplitude modulation is observed. The computation of residual spectra obtained by means of conditioned spectral analysis proves that the diesel pump is involved in the amplitude modulation. Experiments are carried out to validate this diagnosis. Added masses appropriately placed on the injection circuit strongly attenuate the phenomenon.     

Investigation of the optical gain and noise figure for multi-channel amplification in EDFA under optimized pump condition

We present the results of an investigation of optical gain and noise figure for simultaneous multi-channel amplification of an erbium doped fibre amplifier (EDFA) under optimized pump condition. Different pump configurations with varying input signal levels show interesting features on gain flatness. In the experiment, population inversion along the fibre length which determines the gain-spectra and noise characteristics of the amplifier is adjusted through optimized fibre length and injected pump power in order to minimize the gain-tilt at C-band. It is observed that bi-directional pumping manifests the best combination of low noise and high gain of EDFA which are useful as in-line repeaters in WDM network. We obtain 30 ± 1.5 dB intrinsically flat small signal gain from 1538 nm to 1558 nm band of wavelength with noise figure <4 dB for 16-channel simultaneous amplification in a single stage EDFA without gain flattening filter.     

The neutron spin phase imaging technique applied to dia- and paramagnetic samples

We report on a novel application of the Neutron Spin Phase Imaging technique, by performing polarised neutron radiography on dia- and paramagnetic samples. In order to achieve the necessary sensitivity we employed a 2.5 T Ramsey apparatus which was used in a previous experiment to measure the spin-dependent neutron scattering length of the deuteron. First successful results on aluminium, lead, titanium and heavy water (D₂O) samples are presented. They are in good quantitative agreement with expected values deduced from susceptibility measurements.     

Data processing technique applied to the calibration of a high performance FPA infrared camera

The present work deals with the calibration of a focal plane array infrared camera whose detector is a matrix of 320×244 PtSi sensors active in the range 3.6–5 μm. The calibration curve has been obtained by measuring the energy emitted by a blackbody, consisting in a copper cylindric cavity with isothermal walls. The results, obtained in the temperature range 10–70 °C, enable us to investigate the nature of the noise which affects the measurements. The aim is to suggest a data processing and a calibration technique in order to enhance the image quality and the instrument response as well. The effects of random uncertainties have been reduced by using Wiener filtration, which enables us to improve the signal to noise ratio. The problem caused by the nonuniform response of the detector array has been handled by using a different calibration curve for each sensor. The effectiveness of this procedure has been checked by comparing the frequency histograms of the raw and the processed signal. The investigation enables us to highlight some peculiar features of the new focal plane array technology employed in the new generation infrared cameras.     

Pulse analysis method as applied to one of the problems of micro- and nanooptics

The possibility of applying the pulse method to analyze operation of a multicomponent optical system, i.e., the Fresnel lens, exposed to signals of various shape and duration is shown. In particular, this method makes it possible to study random trains of femto- and attopulses and non-monochromatic radiation. The problem is especially urgent in connection with prospects for application of ultrashort pulses in solving scientific, technical, and technological problems of micro- and nanoelectronics.     

Prediction method for listening score and psychological impression taking into account hearing loss due to factors such as aging

This paper considers how the listening scores obtained for audio signals and psychological impressions for speech audibility change when factors such as hearing loss due to aging are taken into account. Concretely, frequency filters for simulating hearing loss due to factors such as aging are first prepared. Next, psychological listening experiments are conducted in which both the audio signal and the noise passing through the above-mentioned filters are transmitted to subjects with normal hearing. Using the observed experimental data, the relationships between the weighted-mean spectral distance and the listening scores of the audio signals and psychological impressions with respect to speech audibility are investigated. Next, based on these relationships, problems associated with the prediction of listening scores of audio signals and psychological impressions with respect to speech audibility are discussed. The predicted results are in good agreement with the observed values.     

Long-term memory contribution as applied to the motion of discrete dynamical systems

We consider the evolution of logistic maps under long-term memory. The memory effects are characterized by one parameter, alpha. If it equals to zero, any memory is absent. This leads to the ordinary discrete dynamical systems. For alpha=1 the memory becomes full, and each subsequent state of the corresponding discrete system accumulates all past states with the same weight just as the ordinary integral of first order does in the continuous space. The case with 00.15 the memory effects win over chaos.     

A fast technique applied to the analysis of Resistive Wall Modes with 3D conducting structures

This paper illustrates the development of a “fast” technique for the analysis of Resistive Wall Modes (RWMs) in fusion devices with three-dimensional conducting structures, by means of the recently developed CarMa code. Thanks to its peculiar features, the computational cost scales almost linearly with the number of discrete unknowns. Some large scale problems are solved in configurations of interest for the International Thermonuclear Experimental Reactor (ITER).     

Defect silicene and graphene as applied to the anode of lithium-ion batteries: Numerical experiment

Mechanical properties and stability of two layers of defect silicene supported by graphene sheets, between which the lithium ion passes under an electrostatic field, are studied by the molecular dynamics method. Defects are mono-, di-, tri-, and hexavacansies. Graphene and silicene edges are rigidly fixed. Graphene sheets contacting with silicene take a convex shape, deflecting outward. Mono- and divacancies in silicene tend to a size decrease; larger vacancies exhibit better stability. The ion motion control using an electric field becomes possible only using perfect silicene or silicene with mono- and divacancies. The ion penetrated through larger defects, and its motion in the silicene channel becomes uncontrolled. When the ion moves in the channel, the most strong stress spikes appear in silicene containing monovacancies. In the case of fixed edges, perfect silicene intercalated with a lithium ion is inclined to accumulate larger stresses than silicene containing defects.     

Performance evaluation of an optical flow technique applied to particle image velocimetry using the VSJ Standard Images

A Dynamic Programming based Optical Flow technique has been applied to the Particle Image Velocimetry (PIV) problem. It has been used for the extraction of dense velocity fields in a planar section of a fluid flow illuminated by a thin laser light sheet. Two (in-plane) components of the velocity vectors can be recovered using a single camera and all three components can be recovered using two or three cameras. Quantitative performance tests have been carried out on calibrated synthetic image sequences from the PIV Standard Project of the Visualization Society of Japan (VSJ). Results are presented for the 2D flow based sequences (STD01 to STD08 Standard Images) and the 3D flow based sequences (STD301, STD302, STD331 and STD337 Standard Images). The RMS error is within the 2–3% range and within the 4–8% range for recovery of the two-component and the three-component velocity vectors respectively.     

Objective and subjective evaluation of acoustic comfort in classrooms: A comparative investigation of vernacular and modern school classroom in Kerala

This paper reports a comparative investigation on acoustic comfort of classrooms in vernacular and modern school buildings in tropical warm humid climate. In this type of climate the intrusion of external noise into the classrooms along with cross ventilation is unavoidable. Preliminary investigation on the evaluation of acoustic comfort carried in secondary schools located in Kollam district of Kerala State in India have been reported. As a step ahead, in order to understand the performance of vernacular school classroom in comparison with that of a modern classroom, an initial survey was conducted in classrooms of ten vernacular and 10 modern schools. Further a detail investigation was carried out in a vernacular and modern school building located in the same site. The study was conducted by measuring the two important acoustic parameters viz., background noise and reverberation time which affect the acoustical comfort in the classrooms. The level of satisfaction of the users was evaluated through questionnaires distributed to teachers and students. The result of the scientific analysis was compared to user’s response. The study reveals that modern classrooms are more preferred than vernacular classrooms acoustically, by the teachers and students. The study also confirms a strong need of improving the acoustical comforts in the classrooms.     

Remote spectrophotometry as applied to determination of the degree of mineralization of peat soils in polesie

Regression relations between the first main component, slope of the SBC curve towards the wavelength axis, and the degree of mineralization of peat soils are established from experimental data. Errors in determination of peat soil productivity are estimated using different spectral indices. For practical use it is recommended to measure the spectral brightness coefficients of peat soils in the 0.50–0.75 μm range. B. I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 1, pp. 102–106, January–February, 1998.     

Using transient and steady-state SEA to assess potential errors in the measurement of structure-borne sound power input from machinery on coupled reception plates

Isolated reception plates provide an engineering approach to quantify the structure-borne sound power input from machinery through the measurement of the spatial-average velocity level and structural reverberation times. For applications in building acoustics there are practical and economic reasons to consider using coupled reception plates formed by solid heavyweight walls or floors that are structurally coupled to other building elements. This paper uses transient and steady-state statistical energy analysis to investigate how the errors depend upon the building structure to which the coupled reception plate is connected. It is shown that the problem is twofold. Firstly, in the low- and mid-frequency ranges, the steady-state velocity level on the coupled reception plate is increased by energy returning from other coupled plates. Secondly, the structural decays on the coupled reception plate have significant curvature due to returning energy; hence short evaluation ranges are needed to minimise the error when determining the total loss factor. This leads to a problematic situation where the coupled reception plate appears to give the correct answer due to the error in the energy cancelling out the error in the total loss factor. The latter error can be minimised using short evaluation ranges for the structural reverberation time.