Baigiamajame darbe nagrinėjamas Vilniaus Gedimino technikos universiteto specialiose laboratorijose esančių įrengimų skleidžiamas triukšmas bei jo atsiradimo dėsningumai. Garso lygiui išmatuoti buvo atlikti eksperimentiniai matavimai. Garso lygiai matuoti ir rezultatai įvertinti pagal higienos normoje HN 33–1:2003 pateiktus reikalavimus. Rezultatai pateikti grafiškai ir atlikta jų analizė. Baigiamajame darbe taip pat pateikta apibendrinta keliamos problematikos analizė, triukšmą mažinančių priemonių apžvalga ir analizė, pasiūlytos triukšmą mažinančios priemonės tiriamose laboratorijose. Išnagrinėjus ir nustačius triukšmo šaltinių keliamo garso lygį ir jo atsiradimo dėsningumus, pateikiamos baigiamojo magistro darbo išvados ir pasiūlymai. Darbą sudaro penkios dalys: įvadas, apžvalginė – metodinė dalis, tiriamoji dalis, išvados ir pasiūlymai, literatūros sąrašas. / Noise outspread originated from machines located in laboratories of Transport engineering and Construction engineering faculties of Vilnius Gediminas Technical University and its origination consistency is being investigated in this article. To evaluate the level of sound there was taken experimental measurements. The level of sound measuring and the measurement results evaluation have been made according to requirements prescribed in Lithuanian hygiene standart HN 33 – 1:2003. Investigation results have been presented graphically, their analysis has been made with drawn inferences. There is summarized arisen problem analysis represented in this graduation work. Moreover it is presented review and analysis of noise abatement means, suggested these means implementation possibilities into laboratories. After investigation of the level of sound produced from noise origin and after determination of its originating consistency, conclucions and suggestions have been represented in this final graduation work. This work consists of five parts: introduction, methodical – review part, research part, conclusions and suggestions, list of literature.

A good work environment in school is crucial in order to effectively teach and learn. Two factors that have a strong impact on the environment in a classroom is the lighting and the sound level. Research has shown that both light and sound have an impact on the health, and while a lot of research has been done on the work environment and the impact by different factors, very few studies have focused on how light and sound affect each other. The purpose of this study is to shed light on how the lighting can affect the sound level in a classroom. The results of this study could be used as a reference as to how the lighting should be set up in order to creative the most effective work environment in a classroom. In order to study if the sound level changes depending on the lighting, a quantitative field experiment has been performed. The study took place in a classroom with 6th graders in primary school. During 12 weekdays over a period of 3 weeks, the decibel values were logged to find out whether the sound level changed. During the first week, the original lighting was used. During the second week, the light was dimmed, and during the third and final week, the light was unevenly spread out. The results show that the sound level is indeed affected by the lighting in the classroom. The unevenly spread out lighting setup with a focus on vertical surfaces resulted in the lowest sound level. One conclusion that can be drawn is that more focus on the ambient light affects the students positively. The most important conclusion is that a lighting setup with different luminaires and a variety of the light levels and spread depending of the time of the day and season, is affecting the sound level and work environment in the classroom in a positive way. / En bra arbetsmiljö i skolan är en viktig förutsättning för att kunna förmedla kunskap. Två parametrar som har stor betydelse i ett klassrum är belysningen och ljudnivån. Forskning visar att både ljus och ljud påverkar hälsan men trots mängden forskning gällande arbetsmiljön och dess påverkande parametrar finns det fåtal forskningar som studerar hur ljus och ljud påverkar varandra. Syftet med studien och denna rapport är att öka kunskapen om hur ljussättning kan påverka ljudnivån i ett klassrum i grundskolan. Studien kan användas som underlag för hur klassrum bör belysas för att påverka arbetsmiljön i ett klassrum. För att undersöka om ljudnivå förändras vid förändrad ljusnivå respektive förändrad ljusfördelning har ett kvantitativt fältexperiment utförts. Studien genomfördes i ett hemklassrum för årskurs 6 och under tolv veckodagar under tre veckors tid loggades decibelvärden. Under vecka 1 var klassrummets ursprungliga belysning kvar, under vecka 2 sänktes ljusnivån och sista veckan skapades en ojämn ljusfördelning. Resultaten visar att ljudnivån kan ändras i ett klassrum med hjälp av belysningen, och studien resulterade i att den ojämna belysningen med fokus på vertikala ytor och omfältsljuset gav den lägsta ljudnivån. Slutsatser som kan dras av resultaten är bland annat att mer fokus på omgivningsljuset påverkar elevernas välmående i en positiv riktning. Den viktigaste slutsatsen är ändå att en belysningslösning med tillgång till olika typer av armaturer och möjlighet att kunna variera både ljusnivå och ljusfördelning beroende på lektion och tid på dygnet och årstid bidrar till en bättre arbetsmiljö i klassrummet.

The developments of new types of conductors and increase of voltage level have driven the need to carry out research on evaluating overhead line acoustic noise. The surface potential gradient of a conductor is a critical design parameter for planning overhead lines, as it determines the level of corona loss (CL), radio interference (RI), and audible noise (AN). The majority of existing models for surface gradient calculation are based on analytical methods which restrict their application in simulating complex surface geometries. This thesis proposes a novel method which utilizes both analytical and numerical procedures to predict the surface gradient. Stranding shape, proximity of tower, protrusions and bundle arrangements are considered within this model. One of UK National Grid's transmission line configurations has been selected as an example to compare the results for different methods. The different stranding shapes are a key variable in determining dry surface fields. The dynamic behaviour of water droplets subject to AC electric fields is investigated by experiment and finite element modelling. The motion of a water droplet is considered on the surface of a metallic sphere. To understand the consequences of vibration, the FEA model is introduced to study the dynamics of a single droplet in terms of phase shift between vibration and exciting voltage. Moreover, the evolution of electric field within the whole cycle of vibration is investigated. The profile of the electric field and the characteristics of mechanical vibration are evaluated. Surprisingly the phase shift between these characteristics results in the maximum field occurring when the droplet is in a flattened profile rather than when it is ‘pointed’.Research work on audible noise emitted from overhead line conductors is reviewed, and a unique experimental set up employing a semi-anechoic chamber and corona cage is described. Acoustically, this facility isolates undesirable background noise and provides a free-field test space inside the anechoic chamber. Electrically, the corona cage simulates a 3 m section of 400 kV overhead line conductors by achieving the equivalent surface gradient. UV imaging, acoustic measurements and a partial discharge detection system are employed as instrumentation. The acoustic and electrical performance is demonstrated through a series of experiments. Results are discussed, and the mechanisms for acoustic noise are considered. A strategy for evaluating the noise emission level for overhead line conductors is developed. Comments are made on predicting acoustic noise from overhead lines. The technical achievements of this thesis are summarized in three aspects. First of all, an FEA model is developed to calculate the surface electric field for overhead line conductors and this has been demonstrated as an efficient tool for power utilities in computing surface electric field especially for dry condition. The second achievement is the droplet vibration study which describes the droplets' behaviour under rain conditions, such as the phase shift between the voltage and the vibration magnitude, the ejection phenomena and the electric field enhancement due to the shape change of droplets. The third contribution is the development of a standardized procedure in assessing noise emission level and the characteristics of noise emissions for various types of existing conductors in National Grid.