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  • 1. Bolin, Karl
    et al.
    Bluhm, Gosta
    Nilsson, Mats E.
    Stockholm University, Faculty of Social Sciences, Department of Psychology. Karolinska Institutet, Sweden.
    Listening Test Comparing A-Weighted and C-Weighted Sound Pressure Level as Indicator of Wind Turbine Noise Annoyance2014In: Acta Acoustica united with Acustica, ISSN 1610-1928, E-ISSN 1861-9959, Vol. 100, no 5, p. 842-847Article in journal (Refereed)
    Abstract [en]

    A listening test was conducted to investigate whether A-or C-weighed sound levels are most suitable as indicator of annoyance due to wind turbine noise. The tests consisted of fifteen different wind turbine noises presented at eight sound levels together with pink noise signals as reference sounds. A total number of 31 persons performed the listening test divided into two subgroups. The first group comprising of 20 students conducted the test in a semi anechoic chamber, and the second group of 11 residents annoyed by wind turbine noise in their homes, conducted the test in their own homes. Results from both subgroups showed that A-weighed sound levels were a more accurate description of wind turbine noise annoyance than C-weighed sound levels. The residents found the same wind turbine noises more annoying than the students, indicating a higher sensitivity to wind turbine noise among persons a priori annoyed by this noise and exposed to this source in their residential settings.

  • 2. De Marchis, M.
    et al.
    Milici, B.
    Sardina, Gaetano
    Stockholm University, Faculty of Science, Department of Meteorology .
    Napoli, E.
    Interaction between turbulent structures and particles in roughened channel2016In: International Journal of Multiphase Flow, ISSN 0301-9322, E-ISSN 1879-3533, Vol. 78, p. 117-131Article in journal (Refereed)
    Abstract [en]

    The distribution of inertial particles in turbulent flows is highly non-uniform and is driven by the local dynamics of the turbulent structures of the underlying carrier flow field. In the specific context of dilute particle-laden wall-bounded flows, deposition and resuspension mechanisms are dominated by the interaction between inertial particles and coherent turbulent structures characteristic of the wall region. The macroscopic behavior of these two-phase systems is influenced by particle inertia, which plays a role at the microscale of a single dispersed element. These turbulent structures, which control the turbulent regeneration cycles, are strongly affected by the wall roughness. The effect of the roughness on turbulent transport in dilute suspension has been still poorly investigated. The issue is discussed here by addressing direct numerical simulation (DNS), at friction Reynolds number Re-tau = 180, of a dilute dispersion of heavy particles in a turbulent channel flow, spanning two orders of magnitude of particle inertia. The irregular wall roughness is obtained through the superimposition of four sinusoidal functions of different wavelengths and random amplitudes. We use DNS combined with Lagrangian particle tracking to characterize the effect of inertia on particle preferential accumulation, looking at the effect of roughness on particle distribution, by comparing the statistics computed for fluid and particles of different size and observing differences in terms of distribution patterns and preferential sampling.

  • 3. Krüger, Jonas
    et al.
    Haugen, Nils E. L.
    Mitra, Dhrubaditya
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Løvås, Terese
    The effect of turbulent clustering on particle reactivity2017In: Proceedings of the Combustion Institute, ISSN 1540-7489, E-ISSN 1873-2704, Vol. 36, no 2, p. 2333-2340Article in journal (Refereed)
    Abstract [en]

    The effect of turbulence on the heterogeneous (solid-fluid) reactions of solid particles is studied numerically with Direct Numerical Simulations (DNS). A simplified reaction system is used, where the solid-fluid reaction is represented by a single isothermal reaction step. It is found that, due to the clustering of particles by the isotropic turbulence, the overall reaction rate is entirely controlled by the turbulence for large Damkohler numbers. The particle clustering significantly slows down the reaction rate for increasing Damkohler numbers which reaches an asymptotic limit that can be analytically derived. This implies that the effect of turbulence on heterogeneously reacting particles should be included in models that are used in CFD simulations of e. g. char burnout in combustors or gasifiers. Such a model, based on the chemical and turbulent time scales, is here proposed for the heterogeneous reaction rate in the presence of turbulence.

  • 4. Lecoeur, Julien
    et al.
    Dacke, Marie
    Floreano, Dario
    Baird, Emily
    Stockholm University, Faculty of Science, Department of Zoology. Lund University, Sweden.
    The role of optic flow pooling in insect flight control in cluttered environments2019In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 9, article id 7707Article in journal (Refereed)
    Abstract [en]

    Flight through cluttered environments, such as forests, poses great challenges for animals and machines alike because even small changes in flight path may lead to collisions with nearby obstacles. When flying along narrow corridors, insects use the magnitude of visual motion experienced in each eye to control their position, height, and speed but it is unclear how this strategy would work when the environment contains nearby obstacles against a distant background. To minimise the risk of collisions, we would expect animals to rely on the visual motion generated by only the nearby obstacles but is this the case? To answer this, we combine behavioural experiments with numerical simulations and provide the first evidence that bumblebees extract the maximum rate of image motion in the frontal visual field to steer away from obstacles. Our findings also suggest that bumblebees use different optic flow calculations to control lateral position, speed, and height.

  • 5.
    Liberman, Michael
    et al.
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Wang, Cheng
    Qian, Chengeng
    Liu, JianNan
    Influence of chemical kinetics on spontaneous waves and detonation initiation in highly reactive and low reactive mixtures2019In: Combustion theory and modelling, ISSN 1364-7830, E-ISSN 1741-3559, Vol. 23, no 3, p. 467-495Article in journal (Refereed)
    Abstract [en]

    Understanding the mechanisms of explosions is important for minimising devastating hazards. Due to the complexity of real chemistry, a single-step reaction mechanism is usually used for theoretical and numerical studies. The purpose of this study is to look more deeply into the influence of chemistry on detonation initiated by a spontaneous wave. The results of high-resolution simulations performed for one-step models are compared with simulations for detailed chemical models for highly reactive and low reactive mixtures. The calculated induction times for H-2/air and for CH4/air are validated against experimental measurements for a wide range of temperatures and pressures. It is found that the requirements in terms of temperature and size of the hot spots, which can produce a spontaneous wave capable to initiate detonation, are quantitatively and qualitatively different for one-step models compared to detailed chemical models. The time and locations when the exothermic reaction affects the coupling between the pressure wave and spontaneous wave are considerably different for a one-step and detailed models. The temperature gradients capable to produce detonation and the corresponding size of hot spots are much shallower and, correspondingly, larger than those predicted using one-step models. The impact of the detailed chemical model is particularly pronounced for the methane-air mixture. In this case, not only the hot spot size is much greater than that predicted by a one-step model, but even at the elevated pressure, the initiation of detonation by a temperature gradient is possible only if the temperature outside the gradient is rather high, so that can ignite a thermal explosion. The obtained results suggest that the one-step models do not reproduce correctly the transient and ignition processes, so that interpretation of the simulations performed using a one-step model for understanding mechanisms of flame acceleration, DDT and the origin of explosions must be considered with great caution.

  • 6.
    Nilsson, Mats E.
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Psychology.
    Alvarsson, Jesper
    Stockholm University, Faculty of Social Sciences, Department of Psychology.
    Rådsten-Ekman, Maria
    Stockholm University, Faculty of Social Sciences, Department of Psychology.
    Bolin, Karl
    Auditory masking of wanted and unwanted sounds in a city park2010In: Noise Control Engineering Journal, ISSN 0736-2501, E-ISSN 2168-8710, Vol. 58, no 5, p. 524-531Article in journal (Refereed)
    Abstract [en]

    Auditory masking of unwanted sounds by wanted sounds has been suggested as a tool for outdoor acoustic design. Anecdotal evidence exists for successful applications, for instance the use of fountain sounds for masking road traffic noise in urban parks. However, basic research on auditory masking of environmental sounds is lacking. Therefore, we conducted two listening experiments, using binaural recordings from a city park in Stockholm exposed to traffic noise from a main road and sound from a large fountain located in the center of the park. In the first experiment, 17 listeners assessed the loudness of the road traffic noise and fountain sounds from recordings at various distances from the road, with or without the fountain turned on. In the second experiment, 16 listeners assessed the loudness of systematic combinations of a singular fountain sound and a singular road traffic noise. The results of the first experiment showed that the fountain sound reduced the loudness of road traffic noise close to the fountain, and that the fountain sound was equally loud or louder than the road traffic noise in a region 20-30 m around the fountain. This suggests that the fountain added to the quality of the city park soundscape by reducing the loudness of the (presumably unwanted) traffic noise. On the other hand, results from the second experiment showed that road traffic noise was harder to mask than fountain sound, and that the partial loudness of both sources was considerably less than expected from a model of energetic masking. This indicates that auditory processes, possibly related to target-masker confusion, may reduce the overall masking effect of environmental sounds.

  • 7.
    Rådsten-Ekman, Maria
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Psychology.
    Axelsson, Östen
    Stockholm University, Faculty of Social Sciences, Department of Psychology.
    Nilsson, Mats E.
    Stockholm University, Faculty of Social Sciences, Department of Psychology. Karolinska Institutet, Sweden.
    Effects of Sounds from Water on Perception of Acoustic Environments Dominated by Road-Traffic Noise2013In: Acta Acoustica united with Acustica, ISSN 1610-1928, E-ISSN 1861-9959, Vol. 99, no 2, p. 218-225Article in journal (Refereed)
    Abstract [en]

    As a complement to conventional noise mitigation, addition of wanted sounds, in particular sounds from water structures, has been suggested as a method for improving noise-polluted acoustic environments. The effect of adding water sounds to road-traffic noise was explored in a listening experiment with 31 listeners. Recordings of road-traffic noise were combined with recordings of waters sounds of varying pleasantness, and the listeners assessed the sounds on eight adjective scales, representing the perceptual dimensions Pleasantness and Eventfulness. The results showed that overall pleasantness increased when a highly pleasant water sound was added to the road-traffic noise. For less pleasant water sounds, no effect, or a decrease in pleasantness, was found. In addition, pleasant water sounds increased perceived eventfulness.

  • 8.
    Sardina, Gaetano
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Picano, Francesco
    Brandt, Luca
    Caballero, Rodrigo
    Stockholm University, Faculty of Science, Department of Meteorology .
    Continuous Growth of Droplet Size Variance due to Condensation in Turbulent Clouds2015In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 115, no 18, article id 184501Article in journal (Refereed)
    Abstract [en]

    We use a stochastic model and direct numerical simulation to study the impact of turbulence on cloud droplet growth by condensation. We show that the variance of the droplet size distribution increases in time as t(1/2), with growth rate proportional to the large-to-small turbulent scale separation and to the turbulence integral scales but independent of the mean turbulent dissipation. Direct numerical simulations confirm this result and produce realistically broad droplet size spectra over time intervals of 20 min, comparable with the time of rain formation.

  • 9.
    Traunmüller, Hartmut
    Stockholm University, Faculty of Humanities, Department of Linguistics.
    Analytical expressions for the tonotopic sensory scale1990In: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Journal of the Acoustical Society of America, ISSN 0001-4966, Vol. 88, no 1, p. 97-100Article in journal (Refereed)
    Abstract [en]

    Accuracy and simplicity of analytical expressions for the relations between frequency and critical bandwidth as well as critical-band rate (in Bark) are assessed for the purpose of applications in speech perception research and in speech technology. The equivalent rectangular bandwidth (ERB) is seen as a measure of frequency resolution, while the classical critical-band rate is considered a measure of tonotopic position. For the conversion of frequency to critical-band rate, and vice versa, the inversible formula z=[26.81/(1+1960/f )]–0.53 is proposed. Within the frequency range of the perceptually essential vowel formants (0.2–6.7 kHz), it agrees to within ±0.05 Bark with the Bark scale, originally published in the form of a table.

  • 10.
    Traunmüller, Hartmut
    Stockholm University, Faculty of Humanities, Department of Linguistics. Fonetik.
    Auditory scales of frequency representation1997Other (Other academic)
    Abstract [en]

    This is an on-line tutorial.

  • 11.
    Traunmüller, Hartmut
    Stockholm University, Faculty of Humanities, Department of Linguistics, Phonetics.
    Conversion between acoustic and auditory units of pitch and calculation of auditory intervals and distances2005Other (Other academic)
    Abstract [en]

    This is an on-line tool for conversions between frequency f (Hz), period P (ms),  Subjective pitch (mel), CB-rate z (bark), ERB-rate (ERB), and musical intervals (semitones, octaves)

  • 12.
    Traunmüller, Hartmut
    Stockholm University, Faculty of Humanities, Department of Linguistics.
    Phase vowels1987In: The psychophysics of speech perception: Proceedings of the NATO advanced research workshop on "The psychophysics of speech perception" / [ed] M.E.H. Schouten, Dordrecht: Nijhoff in cooperation with NATO Scientific Affairs Division , 1987, p. 377-384Conference paper (Other academic)
1 - 12 of 12
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