Sound in the Nature

Imagine if time travel were possible and one could experience the future, i.e. to see and hear an urban or rural environment, which does not exist yet. In fact, this is possible with the tech-nology of Virtual Reality. In virtual reality, almost any environ-ment can be experienced auditory-visually, even if it is in the future. It goes without saying that a halfway correct description of the environment is a very big challenge. But once all charac-teristics of the environment and the sound sources have been specific and implemented, the task of technical realization still remains. This requires a complex Virtual Reality (VR) technology, namely a display device for visual presentation (“3D glasses”) and a 3D audio playback technology (“surround sound technology”). The point is that with technology, both 3D viewing and 3D listen-ing are available in virtually every home. Smartphones already provide rudimentary approaches. Head-Mounted Displays (HMD) have arrived on the computer games market and at corre-spondingly affordable prices. Binaural playback via headphones is both old-fashioned and once again the focus of current re-search when it comes to perfected individualized solutions. The technology is basically available, what do we do with it now? First of all, acoustics in research and practice and also interdisciplinary research with other sciences! Before the introduction to the acoustic-technical basics of virtual acoustics, here is a look at examples: VR technology can be used to plan runways or flight routes near airports. The major challenge here is to characterize the generation of aircraft noise with sufficient accuracy and to generate sound source signals from this, which then reach the receiver via models of atmo-spheric sound propagation. This application will be discussed in more depth below.

Water sounds have always been, and are still nowadays, abso-lutely among the most appreciated natural sounds. Besides its mul-tiple types of emission in terms of loudness, temporal variation and spectral sound distribution, water sounds are rarely interpreted as a negative element. Furthermore, water sounds evoke positive sensations and ex-pectations, and the informational masking of water sounds is effec-tive in mitigating the adverse effects of noise. From a psycho- physiological perspective, listening to water sounds can improve the perceived Restorativeness of a place, induce neural relaxation, or activate the parasympathetic nervous system responsible for stress relief. This review analyses the role of water sound in multi-sensory environments through the investigation performed in several disci-plines. In the first part, we briefly describe the typologies of sounds generated by water, then the effects that water sounds can have on humans, and in the end, are presented the preliminary results of a study on the emotions elicited by water noise conducted at Isola del Liri, a unique historical village in central Italy where inhabitants cohabit daily with a waterfall noise.

The growth of marine biofouling on ship hulls, and chronic in-fections in wounds, have a common foundation in the initial growth of bacterial biofilms over the surface. Biofilms are communities of bacteria that form living ‘aggregates’ that are far more resistant to removal (by chemicals, antibiotics, or mechanical scrubbing) than single (planktonic) bacteria. As it matures, the biofilm forms the foundation in which other species can grow, leading to marine bio-fouling on ship hulls, and chronic infections in human and animal wounds. The existence of chronic wounds in humans shows that current treatments are not wholly effective (the estimated cost of healthcare services in the UK for chronic wounds alone was £5.6 billion in 2017/18). The toxicity of antifoul for hulls, and the effort required to mechanically remove marine biofoulant, has led to the development of through-hull ultrasonic deterrents to reduce bio-fouling growth, but variable performance has stopped widespread adoption. This report introduces new technology that has combined air, sound, and saltwater, to reduce the growth of marine biofouling on hull materials, and removed biofilm from wounded skin, and even promoted skin regrowth over the wounds.

Sound propagation in water is an important factor affecting sub-marine search operations in dive position. Knowing the distribution of sound propagation in seawater is essential for both submarines and surface ships in anti-submarine warfare (ASW) operations. The article is a review and presents examples of sound wave propagation emitted from surface and submarine ships during sea search opera-tions. The aim of the article is to illustrate the propagation of sound waves in sea water depending on the location of the source of sound emitted by surface ships or submarines. Of course, the presented examples are general in nature, typical for ideal images of sound propagation and do not take into account their variability that oc-curs in real situations.

Objective of this article is to emphasise importance of work of in-ventors and scientists that work on development of tools (sonars) that allows for imaging features of water space that is invisible for human senses. The article indicate extent of damage of sea-bottom environment resulting from fishing activity. This activity performed for centuries results in substantial reduction of valuable biological productivity of Batlic Sea waters. The reason was lack of means that allows for easy look into the depths. One of the tool that can be used to evaluate this activity in real time, is hydroacoustic imaging using scanning sonars and multibeam echosounders. Acoustic imaging methods were already utilized to indicate the extent of damage to bottom habitats. Particular areas of the bottom are archeological sites (wrecks) that “document” damage done by fishing and mooring activity and to study influence of this activity on sea bottom envir-onment. Results of these studies give impressive information re-garding scale of possible influence of fishing activity on sea bottom and its biological conditions as well as real reason for the “overfishing”. They also indicate importance of bottom related en-vironmental issues during current and planned extensive offshore activities such as deep sea nodule mining.

Vibration monitoring is a well-known and widely-used techni-que for technical diagnosis of devices. Using this technique, it is possible to foresee an incoming problem with a technical device, and avoid excessive environmental noise pollution. Vibration monitoring mainly uses piezoelectric accelerometers, which are high-precision and wide bandwidth devices, with price being the only serious dis-advantage. Modern MEMS sensors, on the other hand are cheap, but usually with highly limited frequency bandwidth. The latter does not apply to the ADXL100x series of accelerometers by Analog Devices, which have a linear frequency response from DC to 11 kHz and the resonant frequency of 21 kHz. Such devices allow for appli-cation technical diagnosis using cheap hardware solutions. The goal of this paper is to present an example of a portable device built using two ADXL1001 accelerometers and a popular BeagleBone Black development board. The system allows for a maximum of 96 kHz sampling rate, which is more than required for the goal application. The system was tested using a calibration setup with a reference accelerometer.

The acoustic metamaterials are frequently designed using FEA techniques. This paper presents the detailed method of employing the periodic boundary condition and Floquet periodic boundary condition in the FEA software – ANSYS 2022 R1. The procedure operates on APDL (Ansys Parametric Design Language) code in-serted into analysis in Mechanical Application. An example of plate-type metamaterial with antisymmetric periodicity is used for verification of the procedure.

Since first reports in 1949, the application of sonography have been expanded in medicine and ophthalmology.Starting from A-mode ultrasound used for differential diagnosis of retinal detach-ment and choroidal melanoma, to advanced corneal epithelial thick-ness measurement using Very High Frequency enabling more accurate outcome for refractive surgery. In our paper we describe a historical development of ultrasound technique as a diagnostic tool in ophthalmology. We conducted database research, using Pubmed and Google Scholar. As a result we present historical be-ginnings and current interests in ophthalmic ultrasound.