Estimation of the long term average sound level from hourly average sound levels

It is shown how to estimate the long-term average sound level, L_AeqLT (for free flowing road traffic) from measurements of the hourly A-weighted equivalent sound level, L_Aeq1h. To estimate the parameters of the model which describe noise emission and attenuation, concurrent measurements of L_Aeq1h at two distances from the considered road are needed. A semi-empirical formula is derived for L_AeqLT approximation. Also the uncertainty of this approximation is given as a function the distance from the road and receiver height.     

Community response to aircraft noise in Ho Chi Minh City and Hanoi

To formulate Vietnamese and global noise policies, social surveys on community response to aircraft noise and combined noise from aircraft and road traffic were carried out in Ho Chi Minh City from August to September 2008 and in Hanoi from August to September 2009. In total, 1562 and 1397 responses were obtained in Ho Chi Minh City and Hanoi, respectively. The aircraft noise was measured for seven successive days, and the combined noise was measured for 24 h. Aircraft and combined noise exposures ranged from 53 to 71 dB and 73 to 83 dB L_den in Ho Chi Minh City and from 48 to 61 dB and 70 to 82 dB L_den in Hanoi, respectively. The dose–response curve for aircraft noise for Vietnam was established and fitted onto the curve for the European Union. For the same noise exposure, the aircraft noise annoyance in Hanoi was higher than that in Ho Chi Minh City because of the lower background noise level in Hanoi.     

Cross-calibration of participatory sensor networks for environmental noise mapping

Participatory measurements appear as a promising technique for performing noise mapping and monitoring. However, the confidence in the quality of raw data collected through participatory measurements controls the faithfulness of the output noise maps. In this paper, a cross-calibration method is proposed, which aims at both selecting the best candidate sensors and improving the furnished raw data. The method rests upon four steps: (i) an outlier detection, (ii) the crowd sensors-based correction, (iii) a fixed sensors-based correction, and (iv) the L_den estimation. The efficiency of the approach for different characteristics of the network of mobile sensors is evaluated on its ability to reconstruct an artificial reference sound field, which consists of the one-month L_10s evolution, on a twenty streets network. The main conclusions are: (i) the systematic errors of the sensors can be efficiently corrected by a cross-calibration method, and thus do not affect the L_den estimation, (ii) the fixed sensor network helps estimating the average error of the network of mobile sensors, (iii) the dispersion in an individual sensor measurements, which is due for example to the operator, stands for a much more critical concern and should be flagged by a rigorous outlier detection method, as the one proposed in this paper, (iv) although individual measures are improved by the proposed cross-calibration, some errors remain on the L_den estimation because of the shortness of the collected samples, (v) increasing the number of sensors does not improve the L_den estimation as long as individual measurements dispersions remain too large.     

Obtaining calibrated sound pressure levels from consumer digital audio recorders

Audio recording of environmental sound is an increasingly efficient method for autonomously sensing many ecological and anthropogenic processes. The increasing capabilities of consumer digital audio recorders (DARs), especially increases in storage capacity and reductions in power consumption, enable continuous audio recordings exceeding 1 month in duration with packages that are relatively small and inexpensive. To augment the ability of these systems to document the range of sounds present at a location, this paper examines two methods for calibrating recorders to measure sound levels. Compressed audio recorded by a DAR can be processed to yield relatively consistent measures of one-third octave band L_eq values within a limited frequency and dynamic range. This was evaluated by synchronizing data with a Type-1 sound level meter. The calibration is stable over a 23 day deployment outdoors with wide variation in ambient temperature and humidity. When considering aggregate acoustic metrics over time or a wide bandwidth such as an hourly A-weighted L₅₀, the results can be quite accurate (within 1 dBA).     

Assessing methodologies for calculating road traffic noise levels in Ireland - Converting CRTN indicators to the EU indicators (Lden, Lnight)

To comply with the EU Noise Directive 2002/49/EC, Member States are required to produce strategic noise maps for designated areas, including mapping road traffic noise from major roads. These maps must be presented using the EU indicators L_den and L_night. However, the most common noise indicator used in Ireland at present is the L_A10,18h indicator arising from the use of the Calculation of Road Traffic Noise (CRTN) prediction method. Therefore, a relationship needs to be established between L_A10,18h and L_den and L_night, separately. In addition to noise mapping these indicators are used for noise abatement purposes, so the proposed relationship must be accurate and robust. In 2002, the UK’s Transport Research Laboratory (TRL) published a paper describing mathematical procedures that could be used to convert values of L_A10 to L_den and L_night. These procedures were then adopted for use in Ireland. This paper examines the suitability of the TRL conversion methods 1 and 3 for use under Irish road conditions. Method 2 was not considered in this study, as it was a methodology not applicable in an Irish scenario. Studies concluded that where hourly traffic data are available, the conversion methodology outlined in TRL Method 1 is robust and reproducible. However, in the absence of hourly traffic data where daily traffic counts are used, the relevant conversion procedures produce variable results for both L_den and L_night when applied to Irish road conditions. To reduce the variability, new conversion procedures were developed, specifically for Irish road conditions.     

Pilot study on railway noise attenuation by belts of trees

Sound levels from passing trains were recorded. Both maximum A-weighted sound pressure levels L_{A, max} and equivalent levels L_Aeq over 60 second time periods containing each pass-by were measured. Recordings of 15 pass-bys were made at each of two different sites. At each site attenuation over level, grass-covered ground and through shelter belts was measured 1.5 m above ground. Attenuation differences at each site were due to both minor variations in terrain configuration (track above/below adjacent terrain) and to attenuation in vegetation. The latter cannot be separated. L_Aeq attenuations were smaller than L_A,max attenuations, as should be expected. Noise reduction by shelter belts—i.e., the approximate difference between attenuation over grass-covered ground and thouugh vegetation, respectively—was nearly the same, expressed in L_{A, max} and L_Aeq values. Shelter belts selected for this investigation were carefully maintained. Their overall structure, therefore, was very uniform. Behind a dense, 15 year old shelter belt, 50 m wide, consisting of beeches and various conifers planted between older birches and elms, noise levels were 8 to 9 dB lower than in level grass-covered country. Behind a dense, 10 to 20 year old shelter belt, 25 m wide, consisting of oaks, hornbeams, poplars, silver firs and various sorts of bushes, noise levels were 6 or 7 dB lower than in level grass-covered country. The attenuations measured seemed to be of such an order of magnitude that similar belts of trees and bushes could be a means of practical noise reduction. Further investigations, therefore, seem to be worthwhile.     

Size-dependent electronic structures of boron carbonitride (BC2N) nanotubes. A DFT approach

The electronic structures and physical properties of zigzag BC₂N (n,0; n = 4–10) and armchair BC₂N (n,m; n = m = 4–10) nanotubes (type III) are studied by using density functional theory with the generalized gradient approximation. From a comparison of the binding energies, it is inferred that in the large diameter BC₂N nanotubes, the zigzag form is thermally more stable than the armchair form. BC₂N nanotubes (with the exception of (4,0) which is conductor) are gapless semiconductors. Depend on the chirality index, the zigzag forms of BC₂N nanotubes have narrower band gap than the armchair form. Semiconductor character in the studied BC₂N nanotubes is due to contribution of p electrons in the Fermi level. Mulliken population analyses show that significant amounts of electron charge are transferred between atoms; which suggests the existence of polar covalent bonds in the BC₂N nanotubes.     

Detection of extraneous abnormal sounds affecting road traffic noise by use of a necessary condition method

When measuring and/or recording road traffic sound levels during a long time interval, extraneous abnormal sounds will inevitably affect the road traffic sound levels of interest. Such sounds include those produced by horns, sirens, animals, construction sites, and the like. The detection and elimination of such extraneous sound requires much time and effort, but are necessary if noise indices such as L_eq, L_max, and L₁₀ are to be properly estimated. This paper proposes a practical detection method of these extraneous interfering sounds by deriving a necessary condition that road traffic sound levels must satisfy. The necessary condition provides an easy method of identifying sound levels not satisfying the condition, and distinguishes them as extraneous abnormal sounds, even in a large volume of observed data. The validity and usefulness of this method are confirmed by application to actually observed data.     

Noise annoyance assessment of various urban road vehicle pass-by noises in isolation and combined with industrial noise: A laboratory study

Noise maps are diagnosis tools which represent the noise exposure situation using the energy-based index L_den (the day–evening–night level). Two major drawbacks may be attributed to noise maps: (1) energy-based indices only account for one acoustical factor (exposure level) that may give rise to annoyance; (2) combined exposures situations are left unframed.     

Using room acoustical parameters for evaluating the quality of urban squares for open-air rock concerts

Sound quality research of urban squares used for open-air (rock) concerts is very scarce. In contrast to the study of (classical) concert halls, little is known about useful design parameters. For the design of the amplification system, the sound engineer currently often takes into account the desired sound pressure level only.In this study, the ability of existing room acoustical parameters to characterize urban squares acoustically is investigated. An independent parameter set is identified for specific use on such squares. Besides the distribution of the sound pressure level over the square, different impulse response related parameters such as the clarity, center time, reverberation time and bass ratio were considered. In addition, binaural measures were included to measure qualities related to human spatial hearing.This study is based on a measurement campaign, performed at five squares in Belgium before and during life rock concerts. Special attention was paid to the signal processing methodology, given the significant amount of environmental noise often found at such squares during measurements. The variation of these parameters is investigated in relation to the square geometry, the amplification set-up and the presence of delay-lines. Parameters like C₈₀, T₃₀, IACC_E3/L3 and ΔL_eq,A/C were shown to be very useful when characterizing the sound field at urban squares.     

Evaluation and analysis of the environmental noise of Messina, Italy

In this paper, the results of a study on the environmental noise pollution of the city of Messina (Italy) are presented. The investigation has included a preliminary classification of the territory in six acoustically homogeneous areas according to Italian noise regulations. On the basis of the resultant acoustic zoning 35 sites were selected for an experimental survey. This last has been carried out by extensive measurements of the main indexes for noise pollution (L_eq, L₁, L₁₀, L₅₀, L₉₀, L₉₉) and of the traffic flow and composition. Results indicate that: (a) main roads of Messina are overloaded by traffic flow during day-time period and that in all the examined sites daily average sound levels due to road traffic exceed environmental standards by about 10 dBA; (b) environmental noise exhibits a certain degree of spatial variance resulting primarily from the peculiar geo-morphological structure of the town and from the transport infrastructure and (c) more than 25% of residents should be highly disturbed by road traffic noise.     

Stability of matter–antimatter molecules

We examine the stability of matter–antimatter molecules by reducing the four-body problem into a simpler two-body problem with residual interactions. We find that matter–antimatter molecules with constituents possess bound states if their constituent mass ratio m₁/m₂ is greater than about 4. This stability condition suggests that the binding of matter–antimatter molecules is a rather common phenomenon. We evaluate the binding energies and eigenstates of matter–antimatter molecules , and (K⁺μ⁻) − (μ⁺K⁻), which satisfy the stability condition. We estimate the molecular annihilation lifetimes in their s states.     

Quantum phase transitions in Bose–Fermi systems

Quantum phase transitions in a system of N bosons with angular momentum L = 0, 2 (s, d) and a single fermion with angular momentum j are investigated both classically and quantum mechanically. It is shown that the presence of the odd fermion strongly influences the location and nature of the phase transition, especially the critical value of the control parameter at which the phase transition occurs. Experimental evidence for the U(5)–SU(3) (spherical to axially-deformed) transition in odd–even nuclei is presented.     

Annoyance due to railway noise before and after the opening of the Kyushu Shinkansen Line

The development of the Shinkansen railway network in Japan has continued since 1964; however, associated noise and vibration have seriously affected communities located beside the lines. The Kyushu Shinkansen Line (KSL) was opened in 2011 and a second temporary conventional railway line (STL) was operated in 2012. The purpose of this study was to compare community responses to railway noise and vibration before and after the opening of these two lines. Socio-acoustic surveys were performed in Kumamoto from 2009 to 2012, where the conventional and Shinkansen lines are adjacent. The noise and vibration exposures were increased slightly after the opening of the KSL but decreased slightly after the opening of the STL. When multiple logistic regression analysis was applied using highly annoyed/annoyed as the dependent variable and using day–evening–night sound level (L_den) and a dummy variable of before or after the opening of the KSL as independent variables, high annoyance was not changed significantly but moderate annoyance decreased significantly following the opening. There was no significant difference in either high or moderate annoyance between the periods before and after the opening of the STL.     

Statistical scattering theory, the supersymmetry method and universal conductance fluctuations

This paper describes a novel analytical approach to the problem of conductance fluctuations in mesoscopic systems which, in particular, gives account of the influence of the coupling to external leads. We consider the case of a linear disordered sample in the metallic regime, which is coupled to two ideally conducting external leads. Using the many-channel approximation to Landauer's formula, we relate the conductance to the total transmission probability through the sample. The microscopic Hamiltonian of the quasi-one-dimensional disordered sample is formulated in terms of a random matrix, and the elements of the associated scattering matrix which determine the transmission are constructed from statistical scattering theory. We show that in addition to the Thouless energy, E_c, and the mean level spacing, d, there exists in the theory, a third energy scale, Γ, determined by the number of channels in the leads and the strength of the coupling between disordered sample and leads. Related to Γ, is a new length scale, L₀. We find that for sample lengths L >L₀, the properties of the conductance depend only weakly on the coupling to the external leads and, for very large L, become identical with those of quasi-one-dimensional conductors in the weak localization limit. On the other hand, for L < L₀, the coupling to the leads strongly affects the behaviour of both the average and the variance of the conductance. The magnitude of L₀ is typically several magnitudes of ten times the elastic mean free path and thus comparable to the sizes of experimental devices. A further novel aspect of our work is the demonstration that the assumption of GOE statistics for the Hamiltonian is sufficient to yield universal conductance fluctuations.     

Relationships between arithmetic averages of sound pressure level calculated in octave bands and Zwicker’s loudness level

Previously it has been found through a series of psychoacoustical experiments that the arithmetic average of sound pressure level calculated in octave bands is a good estimator of loudness for various kinds of environmental noise. Remarkably, the arithmetic average of sound pressure level in octave bands from 63 Hz to 4 kHz, L_m,1/1(63-4k), strongly correlates with the loudness level specified in ISO 532B, LL(Z), as well as with loudness assessment. To investigate this relationship further, a numerical study has been carried out based on Zwicker’s loudness model. As a result, practical expressions to estimate the loudness levels of general environmental noises from the sound pressure levels in octave bands from 63 Hz or 125 Hz to 4 kHz are proposed.     

Pekeris approximation – another perspective

Inspired on the Pekeris approximation for the centrifugal term, we elaborate a method of resolution for the Schrödinger equation subject to a potential V(r)$V(r)$ of a form more general than the exponential one. Generalizing the Pekeris approximation, we solve the Schrödinger equation with Rosen–Morse and Manning–Rosen potentials including the centrifugal term. The bound state energy eigenvalues for these potentials and for arbitrary values of n and l quantum numbers are presented.     

Unravelling the visible spectrum of strontium monomethoxide

The bands of the A²E–X²A₁ and B²A₁–X²A₁ electronic transitions of SrO¹²CH₃ and the B²A₁–X²A₁ transition of SrO¹³CH₃ have been recorded at high resolution using a laser ablation jet source. The optical–optical double resonance population depletion technique was used to facilitate the assignment of the spectra. Rotational levels with K = 0, ±1 in the X²A₁ and B²A₁ states and K = 0, 1 and 2 in the A²E state have all been characterised. A perturbation affecting the B²A₁ state caused a reversal of the ordering of the spin-rotation components, F₁ and F₂, in the SrO¹²CH₃ isotopologue. This required the introduction of a modified rotational constant B_mod, affecting only the K = 1, F₂ component of the B²A₁ state, in order to model the SrO¹²CH₃ data in a global fit of the A²E–X²A₁ and B²A₁–X²A₁ transitions.     

Development of a 3D finite element acoustic model to predict the sound reduction index of stud based double-leaf walls

Building standards incorporating quantitative acoustical criteria to ensure adequate sound insulation are now being implemented. Engineers are making great efforts to design acoustically efficient double-wall structures. Accordingly, efficient simulation models to predict the acoustic insulation of double-leaf wall structures are needed. This paper presents the development of a numerical tool that can predict the frequency dependent sound reduction index R of stud based double-leaf walls at one-third-octave band frequency range. A fully vibro-acoustic 3D model consisting of two rooms partitioned using a double-leaf wall, considering the structure and acoustic fluid coupling incorporating the existing fluid and structural solvers are presented. The validity of the finite element (FE) model is assessed by comparison with experimental test results carried out in a certified laboratory. Accurate representation of the structural damping matrix to effectively predict the R values are studied. The possibilities of minimising the simulation time using a frequency dependent mesh model was also investigated. The FEA model presented in this work is capable of predicting the weighted sound reduction index R_w along with A-weighted pink noise C and A-weighted urban noise C_tr within an error of 1 dB. The model developed can also be used to analyse the acoustically induced frequency dependent geometrical behaviour of the double-leaf wall components to optimise them for best acoustic performance. The FE modelling procedure reported in this paper can be extended to other building components undergoing fluid–structure interaction (FSI) to evaluate their acoustic insulation.