Rain Noise Research Articles

Animal Sound Recognition Based on Double Feature of Spectrogram

Due to existence of different environments and noises, the existing method is difficult to ensure the recognition accuracy of animal sound in low Signal-to-noise (SNR) conditions. To address these problems, we propose a double feature, which consists of projection feature and Local binary pattern variance (LBPV) feature, combined with Random forest (RF) for animal sound recognition. In feature extraction, an operation of projecting is made on spectrogram to generate the projection feature. Meanwhile, LBPV feature is generated by means of accumulating the corresponding variances of all pixels for every Uniform local binary pattern (ULBP) in the spectrogram. Short-time spectral estimation algorithm is used to enhance sound signals in severe mismatched noise conditions. In the experiments, we classify 40 kinds of common animal sounds under different SNRs with rain noise, traffic noise, and wind noise. As the experimental results show, the proposed framework consisting of shorttime spectrum estimation, double feature, and RF, can recognize a wide range of animal sounds and still remains a recognition rate over 80% even under 0dB SNR.

Application of Daubechies Wavelet Transformation for Noise Rain Reduction on the Video

Currently, the use of digital video in the field of computer science is increasingly widespread, such as the process of tracking objects, the calculation of the number of vehicles, the classification of vehicle types, vehicle speed estimation and so forth. The process of taking digital video is often influenced by bad weather, such rain. Rain in digital video is considered noise because it is able to block objects being observed. Therefore, a rainfall noise reduction process is required in the video. In this study, the reduction of rain noise in digital video is using Daubechies wavelet transformation through several processes, namely: wavelet decomposition, fusion process, thresholding process and reconstruction process. The threshold value used in the thresholding process is VishuShrink, BayesShrink, and NormalShrink. The result of the implementation and noise reduction test show that Daubechies db2 level 3 filter gives the result with the biggest PSNR value. As for the type of threshold that provides optimal results is VishuShrink.

Noise as an informational cue for decision-making: the sound of rain delays bat emergence.

Background noise can have strong negative consequences for animals, reducing individual fitness by masking communication signals, impeding prey detection and increasing predation risk. While the negative impacts of noise across taxa have been well documented, the use of noise as an informational cue, providing animals with reliable information on environmental conditions, has been less well studied. In the tropical rainforest, downpours can be intense and frequent. Strong rainfall may impede efficient orientation and foraging for bats that need echolocation to both navigate and detect prey, and can result in higher flight costs due to increased metabolic rates. Using playback experiments at natural roosts, we tested whether two bat species, differing in their hunting strategies and foraging habitats, use rain noise as a cue to delay emergence from their roosts. We found that both species significantly delayed their emergence time during rain noise playbacks versus silence and ambient noise controls. We conclude that bats can use background noise, here the acoustic component of rainfall, as a reliable informational cue to make informed decisions, in this case about whether to initiate foraging trips or remain in the shelter of their roosts. Our findings suggest that environmental background noise can sometimes be beneficial to animals, in particular in situations where other sensory cues may be absent.

The seismic signature of rain

Rain has long been a problem for land seismic surveys. I measured the seismic signature of rainfall using both water dripped from height using a pipette, and natural rain in Winchester, England, over a three month period. My results showed that rain noise is concentrated at frequencies above 80 Hz with a detectable range of less than 1 m. Drops of water landing directly on a geophone result in events with amplitudes nearly 30 times larger than those landing next to the geophone. Items placed on the surface of the ground, such as cables, absorb the energy of the impact and reduce the level of the resulting seismic noise. Burying geophones results in attenuation of rain noise by between 7.7 and 8.6 dB/0.1 m. But, given the effort required to bury geophones, it is likely that data processing algorithms, or the placement of vibration absorbent matting, are likely to be the preferred strategies for dealing with noise.

Soundscapes in shallow water of the eastern Arabian Sea

The study of soundscapes is an emerging field of research that attempts to provide important baseline information on environmental conditions and biological compositions. In this study, the soundscape in shallow waters of the eastern Arabian Sea is explored through passive acoustic measurements in a time series between October 2015 and January 2016. The noise levels in the spectrum generated from two sources, geophony and biophony, have been observed to vary between diurnal and lunar phases and also between seasons. The noise produced by wind and rain in the frequencies ranging from 0.5 to 5 kHz is found to contribute more intensely to the soundscape during the post-monsoon period. However, during early winter, there is no significant contribution from rain noise. Planktivorous and Terapontidae choruses, the two individual fish choruses, were found to be the sources of biophony in our study. Each chorus displays distinct acoustic characteristics with respective spectral peaks at 0.9 and 1.5 kHz. The choruses exhibit a diurnal pattern and higher noise levels are found during the sunset and lunar phases. Both Terapontidae and Planktivorous choruses exhibit high noise levels every night during the post-monsoon period. However, the same pattern of noise levels is not found between Planktivorous and Terapontidae choruses in early winter as the Terapontidae chorus is absent in that period. In particular, the chorus produced by Planktivorous fish is observed to be associated with the lunar phase, and the noise levels are found to be significantly higher during the new moon and lower during the full moon. This study illustrates that passive acoustics is an effective way of monitoring the soundscape and provides valuable information about the temporal patterns of biological sounds in marine ecosystems.

Gender's Perception: Does the rain noise generated underneath metal deck roof system affects occupants comfort?

Occupants' perception towards the value of indoor environment has always been a crucial issue. Having a good quality in an indoor environment influences the way occupants' behave in their daily activities. Moreover, there are differences on the gender perspective on how they perceive the value of indoor environment. However, gender perception towards rain noise effects in relation to students' activities has been overlooked until today. From the findings it can convey beneficial information regarding the quality of life towards students' living. Conclusively, the overall finding reveals those female students are more annoyed compared to the opposite gender.

The seismic signature of rain

Rain has long been a problem for land seismic surveys, in terms of its effect on the condition of the surface and near surface, and also due to the seismic noise it creates when raindrops hit the ground. I measured the seismic signature of rainfall using water dripped from height using a pipette and natural rain in Winchester, England, over a three-month period. My results indicated that rain noise is concentrated at frequencies of greater than 80 Hz with a detectable range of less than 1 m. Drops of water landing directly on a geophone result in events with amplitudes nearly 30 times larger than those landing next to the geophone. Items placed on the surface of the ground, such as cables, absorb the energy of the impact and reduce the level of the resulting seismic noise. Burying geophones results in attenuation of rain noise by between 7.7 and [Formula: see text]. But, given the effort required to bury geophones, it is likely that data processing algorithms, or the placement of vibration-absorbent matting, are likely to be the preferred strategies for dealing with the noise.

Research on masking effect of multiple natural sounds for monotone-like tinnitus

This paper focuses on whether masking signal with natural sounds is an effective way for mitigating annoyance caused by monotone-like tinnitus. Four natural sounds, pink noise, and narrow bandwidth noise were applied as maskers in the present study shown in this paper. Two monotones were applied as maskees. As a basis for research, natural sounds do not necessarily mask monotones entirely. According to the results, spring water and rain noise can be selected as effective noise for masking monotones. In the case of monotones with different frequency, the same masker performed a little differently on masking. We preliminarily demonstrated the feasibility of natural sounds for masking monotone-like tinnitus, which is of great use for improving maskers in tinnitus masking therapy.

Experimental studies on the rain noise of lightweight roofs: Natural rains vs artificial rains

Rain noise is often an unpleasant problem that disturbs people’s activities significantly in buildings with lightweight roofs, however, the existing researches are all based on artificial rains in laboratory, while the characteristics of natural rain noise as well as the relationship between actual rain noise and laboratory measurements still need to be explored to fulfill practical demands. This paper first presents two experiments on natural rain noise, revealing that rain intensity is the decisive factor of natural rain noise for heavy rains, and the A-weighted sound pressure level of rain noise caused by heavy rains is proportional to the logarithm of rain intensity. Furthermore, three more experiments on the rain noise with artificial rains are carried out, indicating that differences in rain intensities, fall heights and raindrop size distributions are the factors that cause significant deviation between actual rain noise and laboratory measurements. This total deviation as well as the deviations caused by each factor are then quantified. Finally, a method to predict the actual rain noise of a certain roof using laboratory measurement results is provided, which can be useful in real projects as an effective substitute of experiments using uncontrollable real rains.

Reduction of Gaussian, Supergaussian, and Impulsive Noise by Interpolation of the Binary Mask Residual

In this paper, we present a new approach for noise reduction. A binary time-frequency (T-F) masking threshold criterion is proposed and analyzed with respect to the average spectra of music and noise disturbances. Modified autoregressive (AR) detection and AR interpolation are then applied to the residual signal of the binary masking process. The proposed method is able to reduce supergaussian and impulsive noise while ensuring preservation of the desired signal, which is crucial for professional high-quality audio restoration, and it is also suitable for Gaussian noise to a certain extent. The approach is compared to a state-of-the-art restoration algorithm by means of the objective measures signal-to-noise ratio (SNR) improvement and perceptual quality, and by subjective listening tests. The objective results as well as the listening tests show that the proposed algorithm is especially suited for supergaussian, grainy-sounding noise types, e.g., optical soundtrack noise of celluloid movie footage, or rain noise.

Ambient noise during rough weather and cyclones in the shallow Bay of Bengal

This paper presents ambient noise analysis during rough weather, using time series measurements from an automated noise measurement system in the shallow southwest Bay of Bengal during October–November 2010. The period witnessed low-pressure events including depressions and cyclones, with JAL cyclone passing close to the measurement site. The time series noise level shows a shift in mid-October, after which deep depressions and cyclones formed, with an average increase of 5–10 dB in the lower band and 2–3 dB in the higher band of frequencies. Furthermore, correlation between noise level and wave height (data from wave rider buoy deployed at the site) for sea state scale 3 and above shows good correlation with an increase in noise level with increase in wave height, the effect being most pronounced at 0.5 kHz. The noise captured during JAL was analysed to identify the spectrum components due to convective precipitation and heavy wind/wave activity and shows anomalously high levels during the crossing of the cyclone. Rain noise spectra from the rain bands associated with the wall of the cyclone are reported. This has been correlated with radar reflectivity measurements to ascertain the presence of rain, and discriminate between convective and stratiform types. Also, vertical directionality pattern of ambient noise during JAL showed clearly distinct surface contributions. On the whole, knowledge of ambient noise fields during high sea states and precipitation is useful in optimizing SONAR performance. The findings at the study site have been compared with measurements from other shallow water locations during rough weather.

Reduction of rain noise from Ethylene/TetraFluoroEthylene membrane structures

Ethylene/TetraFluoroEthylene (ETFE) is a kind of fluororesin, which is recently used for outer skins of many sports facilities because of its weatherability and lightweight properties. Herein, rain noise from an air-cushion-membrane structure with ETFE films is investigated. An analytical prediction model is proposed and the model is verified by the laboratory experiment based on ISO 140-18. To control the noise, some samples with nonwoven fabrics and gel sheets were tested. The theoretical and experimental results show the possibility of attenuating the noise by adding absorptive layers and/or damping materials.

The depth-dependence of rain noise in the Philippine Sea

During the Philippine Sea experiment in May 2009, Deep Sound, a free-falling instrument platform, descended to a depth of 5.1 km and then returned to the surface. Two vertically aligned hydrophones monitored the ambient noise continuously throughout the descent and ascent. A heavy rainstorm passed over the area during the deployment, the noise from which was recorded over a frequency band from 5 Hz to 40 kHz. Eight kilometers from the deployment site, a rain gauge on board the R/V Kilo Moana provided estimates of the rainfall rate. The power spectral density of the rain noise shows two peaks around 5 and 30 kHz, elevated by as much as 20 dB above the background level, even at depths as great as 5 km. Periods of high noise intensity in the acoustic data correlate well with the rainfall rates recovered from the rain gauge. The vertical coherence function of the rain noise has well-defined zeros between 1 and 20 kHz, which are characteristic of a localized source on the sea surface. A curve-fitting procedure yields the vertical directional density function of the noise, which is sharply peaked, accurately tracking the storm as it passed over the sensor station.

A New Algorithm of Rain (Snow) Removal in Video

The images acquired by outdoor vision system in the rain or snow have low contrast and are blurred, and it can cause serious degradation. Traditional rain (snow) removal method is restricted with the intensity, so the effect is not ideal. According to the characteristic of vision system acquiring multiple different degraded images in a short time, the paper processes multiple images to realize restoration. Snow and rain have the dynamic characteristic that the direction, intensity and shape of rain and snow are unfixed, which makes it difficult to establish unified physical model in the spatial domain. But analyzing them in the frequency domain doesn’t affected by the dynamic characteristic. From the perspective of frequency domain, the paper uses the method of wavelet multi-level decomposition and wavelet fusion to determine the number of layers of rain (snow) noise, formulates a fusion rule based on rain (snow) noise pollution, and makes wavelet fusion on specific layer of multiple continuous degraded images for achieving the objective of rain (snow) removal. Simulation results indicated that the method in the paper not only has ideal restoration results, but also is not restricted by noise intensity.

A Consolidated Theory for Predicting Rain Noise

A Consolidated Theory for Predicting Rain Noise

A Consolidated Theory for Predicting Rain Noise

This paper presents a theory for rain noise prediction, consolidating discussions of drop impact on a plate and resulting work on rain noise predictions that is found in the literature. An objective of the consolidated theory is a robust engineering model which does not rely on complex computational techniques or lengthy computer simulation. The model described is compared to measured data to establish accuracy and reliability.

Underwater and air sound signals in the case of a droplet falling onto a liquid surface

Among fast natural phenomena, exchange pro� cesses involving the atmosphere and the ocean are of particular interest. These processes include the inter� action of rainfall (first of all, rain) with the oceanic surface. The kinetic energy of a rain droplet and the surface energy that becomes free once the droplet has been absorbed result in a series of hydrodynamic phe� nomena. These are formation of a cavern, a cumula� tive jet, streamers, regular capillary waves, and irregu� lar waves. The formation and fillingin of the caverns are accompanied by the detachment of air cavities of both regular and irregular shape, with a part of them emitting sound. The acoustic rain noise generated by falling drop� lets forms the total sonic background. This is an important source of information on the intensity and localization of rain, which is a significant fraction of the total ocean acoustic noise (1). In records of under� water signals obtained within the rain period, the spec� tral peak between 10 and 15 kHz is surely localized (2). Modernization of experimental methods has opened the possibility to measure fluctuations of sound pressure in water, which arise as a result of the fall of both the set of (rain) droplets and an individual droplet with the simultaneous registration of the flow pattern (2). Among competing mechanisms of sound emission, the impact pulse, hydrodynamic impact, and aircavity resonances were analyzed. In experi� ments, along with the sound registration, air bubbles were always observed. Therefore, basic attention was paid to the resonance mechanism for which the soundemission frequency was connected to the bub� ble size by a simple calculation relationship (3). The available experimental data made it possible to obtain a diagram of flow modes in the plane of the dropletfall velocity as a function of the droplet diam� eter. In this plane, a region of stable registration is iso� lated for gas bubbles of the size corresponding to the spectralpeak frequency (4). However, for the reso� nance mechanism, the question remained open on the transformation of the fallingdroplet energy to that of bubble resonance vibrations accompanied by sound emission. In further experiments, it was noted that gas cavities emit underwater sound in the course of recon� structing their irregular shape (with tapers and folds) to the equilibrium (spherical) one. This process is accompanied by the liberation of the potential surface energy (5). The analysis of the processes allows for the fact that a falling droplet leads to accepting the substance liq� uid, the momentum, and the mechanical energy, which results in generating visible and latent flows of different scales. Caverns, coronas, cumulative jets, and streamers correspond to visible flows and manifest themselves in the changing the shape of the free sur� face (6). Largescale latent flows cause chaotic displace� ments of gas bubbles in the bulk of the liquid. The vir� tually unstudied finestructure latent flows manifest themselves in peculiarities of both the freesurface shape and the substancetransport pattern near the interface. They also determine the properties of emit� ted sound packets. In the present paper, for the first time, we thoroughly study the frequencytime param� eters of sound signals initiated in air and water by freely falling droplets.

Gender's Perception Towards Rain Noise Falling on Metal Deck Roof System in Relation to Student Activities

Occupants’ perception towards the value of indoor environment has always been a crucial issue. Having a good quality in an indoor environment influences the way occupants’ behave in their daily activities. Moreover, there are differences on gender perspective on how they perceive the value of indoor environment. However, gender perception towards rain noise effects in relation to students’ activities has been overlooked until today. Overall findings on mean scores reveal that both of gender concurred that a communication problem is the most influential activities disturbed when its rain. These findings supported by the physical measurement where the range of rain noise generated underneath metal deck roof system were exceeded 70dB which significantly trigger a masking effect of speech of the occupants. Meanwhile, t-test finding reveal those female students are more annoyed towards rain noise compared to the opposite gender

Noise Generated by Raindrop on Metal Deck Roof Profiles: It's Effect towards People Activities

Noise generated by rain fall on un-insulated metal deck roofs can cause serious acoustic problems in buildings. This paper reports the outcomes of an effect of sound created by rain fall on un-insulated metal deck roofs towards people's activities. The measurement and questionnaire distribution was done at selected UiTM buildings that have been built using un-insulated metal deck roofs. It was found that the occupants facing inconveniences condition that can disturb their activities. The comfort noise level that accepted by the human being is between 55 to 60dB. Therefore, this study substantiates the notion that rain noise can contribute to negative effects in people's lives during rain.

Occupants’ responses on rain noise underneath metal deck roof system

The design of metal deck roof system should incorporate some sound insulation materials if it were to insulate structure borne impact noise such as from the rain, transmitted into a building. The noise from the rain may affect the ambient noise level within the space underneath the roof thus affect the occupants’ comfort. Thus, this paper would like to examine the relationship between the annoyance responses with noise disturbance on occupants’ activities and side effects face by occupants’. The result reveals the impact from rain noise amplified by metal correlated with annoyances which cause uncomfortable condition to the occupant.