Sound intensity investigation of the acoustics performances of high insulation ventilating windows integrated with rolling shutter boxes

High sound insulation ventilating windows (HSIVW) were recently proposed for noise control in buildings close to motorways or railways, where noise barriers are not effective or too expensive. These windows are characterized by good insulation performances and at the same time allow airflow through the window itself; such a performance matches summer indoor ventilation and refreshment needs.In the last years at the Acoustics Laboratory of the University of Perugia various prototypes were tested and their acoustic and airflow performances were assessed, also verifying the influence of filtering systems in the aerator.In the present paper a lot of experimental data are presented and in particular the results of a recent campaign, aimed at testing windows samples integrated with insulated rolling shutter boxes are presented. Sound reduction index R and single number sound reduction index R_w are evaluated, considering different exercise conditions; acoustic intensity measurements and analysis have also been performed, in order to verify the parts of the window which need to be optimized.     

Feedback control of sound transmission through a double glazed window

One way to tackle the control of stochastic noise in three dimensions is to reduce the sound transmission to the zone of interest. In buildings, windows are often the weak link in protecting the interior from outside noise. In particular, double glazed windows have a poor sound insulation at low frequency around the mass-air-mass resonance (double wall resonance). Since passive means for windows are exhausted, an active controller that increases the transmission loss in the low-frequency range is an attractive approach to reduce the noise level in buildings. Previously suggested feedforward controllers need reference microphones to measure the disturbance outside and error microphones for the adaptation somewhere in the room. For a real window this is unpractical or even unfeasible. These limitations can be overcome with the feedback controller presented here, which only uses sensors and actuators in the cavity of the double glazed window. Four different controllers—two feedforward and two feedback strategies—are designed, implemented and compared. With feedback the noise transmission around the mass-air-mass resonance can be reduced by , compared to with a feedforward controller.     

The use of in-situ test method EN 1793-6 for measuring the airborne sound insulation of noise barriers

The in situ measurement of the airborne sound insulation, as outlined in EN 1793-6:2012, is becoming a common means of quantifying the performance of road traffic noise reducing devices. Newly installed products can be tested to reveal any construction defects and periodic testing can help to identify long term weaknesses in a design. The method permits measurements to be conducted in the presence of background noise from traffic, through the use of impulse response measurement techniques, and is sensitive to sound leakage. Factors influencing the measured airborne sound insulation are discussed, with reference to measurements conducted on a range of traffic noise barriers located around Auckland, New Zealand. These include the influence of sound leakage in the form of hidden defects and visible air gaps, signal-to-noise ratio, and noise barrier height. The measurement results are found to be influenced by the presence of hidden defects and small air gaps, with larger air gaps making the choice of measurement position critical. A signal-to-noise ratio calculation method is proposed, and is used to show how the calculated airborne sound insulation varies with signal-to-noise ratio. It is shown that the measurement results are influenced by barrier height, through the need for reduced length Adrienne temporal windows to remove the diffraction components, prohibiting the direct comparison of results from noise barriers with differing heights.     

Active control of aircraft fly-over sound transmission through an open window

This paper presents an experimental work on active control of sound transmission through a restricted opening bottom hinged window. The main goal of the work is to demonstrate the feasibility of the active technique to limit the loss of attenuation due to the aperture of windows, and its application to aircraft fly-over incident noise. The experimental window is placed in an exposed façade of a dwelling close to an airport and subject to fly-by aircraft noise. The active control is configured to cancel the pressure at the aperture using a single-input single-output feedforward adaptive system. As a result, a reduction of sound transmission is achieved with low power consumption. In global terms, an increase of almost 3 dB of transmission loss (with respect to the partially opened window insulation values) in the low frequency range (below 160 Hz and according to the National Danish Method for evaluating low frequency noise) is demonstrated, which is equivalent to a reduction of 50% in the loss of insulation caused by opening the window.     

A short method for the determination of airborne sound insulation characteristics in buildings

This paper presents the results of experiments made on a sample of 40 different facades to evaluate the characteristics of airborne sound insulation in buildings. On the basis of these results, some relationships are proposed for correlating the airborne sound insulation index, R_w (ISO 717/3-1982), with the measurements in the field of the equivalent sound pressure level made in dB(A).     

Experimental study for control of sound transmission through double glazed window using optimally tuned Helmholtz resonators

This paper presents an experimental investigation of passively control of sound transmission through a double glazed window by using arrangement of Helmholtz resonators (HRs), which are commonly used for narrow band control application. The laboratory experiments were performed placing the window between reverberation chamber and anechoic chamber. The window was subject to diffuse field, approximate normal wave and oblique wave acoustic excitations. Three sets of HRs were designed and installed in cavity of window. The sound control performances at far-field were measured. The control performances from varying the number of HRs, incident acoustic field, excitation sources (band-limited white noise and traffic noise examples) are presented and discussed in detail. It is shown that a considerable reduction of the transmitted sound pressure levels has been achieved around the mass–air–mass resonance frequency (50–120 Hz). The obtained reductions in the transmitted sound pressure illustrate the potentials of HRs for improving the sound insulation characteristics of double glazed window. The experimental results also indicate that only tuning the HRs to the mass–air–mass resonance frequency does not guarantee the best possible insulation of the sound transmission.     

Noise from neighbours and the sound insulation of party walls in houses

Nine-hundred-and-seventeen residents in a sample of attached houses constructed since 1970 were interviewed in the course of a national survey dealing with nuisance occasioned by noise from neighbours. The airborne sound insulation of the party walls, measured prior to occupation, ranged from zero to 120 dB AAD. Two-thirds of the respondents heard noise from their neighbours and even at performance levels meeting or exceeding the minimum requirements of the Building Regulations nearly 50% did so. Of the total sample, some 18% were seriously bothered by neighbours' noise. Highly significant relationships were found between physical performance rated in dB AAD (Aggregate Adverse Deviation) and a variety of subjective responses. These include reports of hearing neighbours' noise, of being bothered by it, hearing neighbours' conversation, and, in particular, the direct rating of sound insulation quality by respondents, which last appears to provide the most reliable and consistent indication of the likelihood of experiencing nuisance from neighbours' noise. These results provide, for the first time, empirical validation of the U.K. performance rating procedure. In addition, the survey findings emphasize the importance of impact noises, not included in the standardized performance measurements, but which contribute substantially to nuisance, particularly between houses where airborne sound insulation is comparatively good. Other findings indicate that occupants were very satisfied with their general environment and only slightly less so with their homes. Poor sound insulation was a prominent criticism of the dwellings, being ranked third among spontaneous adverse comments and first in a ranking of nine commonly encountered building defects. These results indicate the importance of sound insulation to occupants of recently built houses, placing this aspect of design and construction within a wider context. The overall results of the survey provide a practical guide to estimating the consequences, in terms of occupants' attitudes to noise from neighbours, of raising or lowering standards of sound insulation performance between houses.     

The sound insulation of partially open double glazing

The sound reduction index has been measured in the laboratory for partially open sliding window units. The object was to test the feasibility of achieving a moderate degree of sound insulation whilst retaining natural ventilation. Assuming source spectra for aircraft and traffic noise and using the measured SRI's, the sound level difference across a window has been calculated in terms of dB(A). It is concluded that partially open double glazing is about 10 dB(A) better than partially open single glazing, and that double glazing can be opened as much as 100 mm and still be as effective against aircraft noise as closed single glazing.     

Standardised acoustic characterisation of sonic crystals noise barriers: Sound insulation and reflection properties

This work presents sound insulation and sound reflection measurements conducted over sonic crystal noise barriers according to the European standards EN 1793-2, EN 1793-5 and EN 1793-6. In most of the reference literature, sound insulation and reflection properties of sonic crystals are measured or a diffuse sound field or in a direct sound field including the top and side edge diffraction effects together with the transmitted (or reflected) components. The aim of this work is to perform free-field measurements over a real-sized sample in order to window out all diffraction components and to verify the points of strength and weakness of the application of standardised measurements to sonic crystals. Diffuse field measurements in laboratory are also done for comparison purposes. Since the target frequency range for traffic noise spectrum is centred at around 1000 Hz, a finite element based parametric investigation is performed to design unit cells capable of generating band gaps in the one-third octave bands ranging from 800 Hz to 1250 Hz. Then, 3 × 3 m sonic crystal noise barriers are installed in the Laboratory of the University of Bologna and sound insulation and sound reflection measurements are performed according to the mentioned active standards for normal incidence. Sound insulation is measured for diffuse incidence too. The two methods give different results. The method more directly comparable to calculations is the free-field one. However, if on the one hand the application of a time window allows to compute the transmitted or reflected component only, on the other hand the time window itself limits the maximum width of the sample for which all reflections of the n-th order having a significant spectral content are included, and thus results critical in the analysis of this kind of noise barriers. Nevertheless, the standardised measurements allow a direct comparison between the performance of sonic crystals and common noise barriers.     

Effect of size on measurements of the sound reduction index of a window or a pane

The variation in the sound reduction index as a function of the size of a test specimen was investigated. Five different sizes of one particular hinged window were tested. In addition, tests were carried out with a sound insulating double glazing and a laminated pane mounted in normal wooden frames.Some differences in the sound reduction index due to the different test specimen sizes were found. However, these differences were slight compared with the practical difficulties and costs which tests on several sizes would involve. One size of test specimen is therefore considered to be sufficient for sound reduction index measurements on windows with respect to labelling. This practice is currently in use in Denmark.     

Numerical analysis and passive control of a car side window buffeting noise based on Scale-Adaptive Simulation

Flow over an open side window in a car exhibits similar characteristics as the flow over an open cavity. Computational Fluid Dynamics (CFD) simulation over a cavity was done as a benchmark. The unsteady flow simulation was carried out using Scale Adaptive Simulation (SAS) turbulence model. The benchmark results, frequency and sound pressure levels of feedback and resonance modes, all well matched with the experimental data. Then, with the right rear window, for example, the mechanism of the side window buffeting was investigated. The simulation results show that side window buffeting noise is generated by large scale vortices and in low frequency. Furthermore, buffeting noise characteristics under several patterns of side windows opening were also numerically investigated. As a result, rear window buffeting noise is more severe than that of front window when one window open, and combination pattern of side windows open can reduce buffeting noise. To decrease the interior noise and improve car ride comfort, four suppression measures through adding a side window weather deflector at the A-pillars, constructing a cavity at the B-pillars, combination of the front and rear windows and installing a row of square cylinder deflector at the B-pillars were also studied, respectively. In conclusion, certain noise reduction can be achieved through four passive control methods.     

基于改进声线跟踪法的室内交通噪声动态模拟

对碰撞点的有效性判断是传统声线跟踪法的一个重要步骤,在计算复杂的室内空间问题时计算量较大,为解决这一问题采用了一种与空间剖分相结合的改进的声线跟踪法。将该方法与微观交通流仿真和车辆噪声排放模型进行结合,实现了道路交通噪声透过窗户在多连通室内空间传播的动态模拟。最后采用该方法对相同道路和交通流条件下不同建筑朝向的4种布局室内噪声进行动态模拟。分析了室内交通噪声的大小和分布与建筑物布局、窗户的朝向、窗户的形式和面积等因数之间的关系。结果表明:窗户正对道路的房间比窗户侧对道路的房间噪声高4～6 d B(A),房间内等效声级与窗户面积的对数成正比关系。     

A review of the metal stud stiffness on the sound insulation of gypsum-board partitions

For the sound insulation of a double-panel partition,the stud between two leaves creates a vibration transmission path,which can often be more critical and more important in the mid-frequency range than the airborne path through the cavity.Owing to the fact that partitions with light-weight steel studs are commonly used in building construction,studies on the sound insulation effect of such studs have been conducted.Especially,a model,initiated by Gu and Wang(1983),has been widely studied during the past decades.In the model,the steel stud is considered as an elastic spring with its cross-section stiffness in the sound insulation index prediction of such a partition.Experimental results of different stud profiles have been reported from different testing laboratories and more information has been gained to understand the stiffness effect of the stud on the sound insulation of the double-leaf partitions.In this paper,the authors have given this subject a thorough review and have concluded that a critical problem needs further investigation on the determination of the stiffness of the connecting elements in the double-leaf partitions.     

Justification of standardized level differences in rating of airborne sound insulation between dwellings

It has long been recognized that single-number quantities R′_w, D_nT,w or D_n,w result in different conclusions in objective rating of airborne sound insulation between dwellings. The difference between the values of these single-number quantities (SNQ), however, does not prove which of them describes the sound transmission between rooms most correctly. The main object of this article was to study which SNQ correspond best with transmitted living sound levels in buildings when reverberation time, volume of receiving room and sound insulation are taken into account. Data of 100 field measurements of airborne sound insulation were collected as well as 207 reverberation times of furnished rooms. The transmitted sound levels of living sounds were evaluated on the basis of known living sound spectra and measured level differences D. The results show that the SNQs standardized to reference reverberation time of 0.5 s lead in all cases to best correlation between the SNQs and the sound levels of transmitted living sounds. It was also checked whether the rating by D_nT,w would lead to higher transmitted sound levels of living sounds in larger rooms, but this was not detected. The use of D_nT,w makes rooms of different volumes equal in regard to required sound insulation between them. It is thus justified to replace R′_w with D_nT,w as the SNQ for rating the airborne sound insulation. Widening the frequency range down to 50 Hz or up to 5000 Hz did not give noteworthy improvement in the correlation.     

Mechanisms of active control of noise transmission through triple-panel system using single control force on the middle plate

This paper presents an active triple-panel sound insulation structure with an idealized controllable point force acting on the middle plate. A novel analytical approach based on sound energy transmission rule is proposed to achieve the physical mechanism study. The transfer impedance matrix of the incident and middle plate is calculated using numerical approach. And the rule of sound energy transmission through the triple-panel structure is concluded by indirectly analyzing the radiated sound power of the three plates. Finally the physical mechanism of noise insulation is investigated from the point of view of the change in behaviors of energy transmission in controlled and uncontrolled conditions. Results obtained demonstrate that there exist four different energy transmission paths for four panel mode groups. The energy transmission is independent in each path and they are all of band-pass characteristic. The role of the middle plate and two cavities is very similar to the band-pass filter whose pass-band is different for different mode groups. The essence of active noise insulation lies in the fact that the energy transmission in each path is suppressed in its pass-band after control. This greatly improves sound insulation capability of the triple-panel structure and leads to sound propagation being blocked.     

实验室隔声测量中试件洞填隙墙传声影响的检验

文章探讨了实验室建筑构件隔声测量中填隙墙传声影响的检验与修正方法。通过实验分析,给出了三种可用于不同隔声量构件的门、窗和玻璃试件隔声测量的填隙墙构造方式。     

Digital audio information hiding based on Arnold transformation and double random-phase encoding technique

In this paper, Arnold transformation and double random-phase encoding technique widely used in digital image information hiding are introduced to digital audio information hiding. The digital audio is transformed into a 2-D image called sound map and then the sound map will be divided into many windows and each window will be encrypted based on the Arnold transformation. Finally sound map will be re-encrypted based on double random-phase encoding technique. This method offers many advantages for digital audio information hiding: improve security and high attack immunity.     

Effect of frame construction on the sound insulation of unsealed windows

The sound insulation of two sets of unsealed windows with different frame cross-sections has been examined. One set of frames was constructed in situ using rectangular timber sections, the others being proprietary steel windows. The results showed that the unsealed steel windows had much lower sound insulations than the unsealed timber windows for gaps of the same length and width. The differences are discussed in terms of the cross-sectional shapes of the respective gaps.