Active headsets have been on the market for years and now it is time for something else to enter the stage. The technology of active noise reduction can for exmple also be used in ventilation systems for reducing ventilation noise. An active control system principally consists of four important components, namely the downstream error microphone, the upstream detection or reference microphone, the digital signal processor (DSP) and a loudspeaker. The upstream reference microphone listen to the primary ventilation noise and sends it to the DSP which makes a phase shift to the signal and sends it to the loudspeaker. The loudspeaker sends out the opposite waveform of the incoming one and reduce the primary ventilation noise.

The report examines the factors which may be a contributing cause to the problems that are present when ferritic stainless steel are eddy current tested in a warm condition. The work is carried out at Fagersta Stainless AB in Fagersta which manufactures stainless steel wire. In the rolling mill there is an eddy current equipment for detection of surface defects on the wire. The ferritic stainless steels cause a noise when testing and this noise complicates the detection of defects.Because of this, a study was made of how the noise related to factors such as steel grade, temperature, size and velocity. By observing the signal and with the possibilities to change the equipment settings the capability to let a signal filter reduce the noise level were evaluated.

Too high levels of noise lead to various health problems and cost society billions of SEK peryear. In this thesis we have examined a model of the A40E articulated hauler at VolvoConstruction Equipment in Braås. We have tried to reduce cabin noise in an articulated hauler,while also providing a way on how to proceed with a machine when the cabin does not measureup to the sound requirement. The best way to find leaks were with a reference source of model4205 and its speaker HP 1001 from Brüel & Kjaer in the cab and then walk around and listen towhere the reference source was more prominent. In this way, we found that the edges and theplugs were sensitive areas.

Wind power in Sweden is expanding in response to the government's decision that 49% of Sweden's power should originate from renewable energy sources by the year 2020. Problems with noise and sound emissions related to wind turbines are a constant argument against the wind power expansion and this paper means to examine if vertical axis wind turbines might be a viable alternative to the conventional horizontal design for noise sensitive areas. In order to determine factors like difference in frequency, noise propagation and noise emission level, measurements of both horizontal and vertical axis wind turbines have been completed and the data analyzed with MATLAB. It is shown that there is a difference in how the noise from the two types of turbines propagates due to avariation in the frequency spectra of the emitted sound. It is also shown that vertical axis wind turbines generate a lower sound emission with less intensity inthe lower frequencies..

This paper describes a method for wireless energy transfer via near-field electromagnetic inductionthat is inexpensive, simple and can be applied to almost any type of system, regardless of size andenergy demands.The method uses a primary unit consisting of an oscillator, amplifier and inductive coil thattransfers energy to a secondary unit consisting of a coil, rectifier and voltage regulator. Two typesof oscillators and several amplifier designs were realized and evaluated together with a multitudeof flat coils of both monofilar and bifilar type.The results show that it is important to use an oscillator whose frequency is dependent on theinductance of the connected transmission coil, such as the Colpitts oscillator. This is preferable toan oscillator with a preset frequency, such as a Schmitt-trigger oscillator..

Noise is a growing health problem. People are not always aware of the injuries that noise can cause. The media culture of today has a big influence on teenagers. This is caused by portable music players, computers, concerts etc. The schools are having larg classes and that can cause a lot irrelevant speech during lessons.

This project started when LIC Audio AB wanted help with development of a hearing aid for public rooms. The problem is that a lot of people suffer from some sort of hearing impairment. In places with a lot of people and background noise the problem becomes bigger and the sound seems to flow together. During the project we found the solution for the problem in the shape of a headphone. The headphone receives a signal from a preinstalled hearing loop.

Noise in schools can have negative effect on the teaching environment and speech perception. The national Child Environmental Health Surveys (BMHE) conducted in 2003 and 2011 studied how 12-year olds experience their sound environment in school. Results showed that the number of pupils that experience annoyance from noise increased from 2003 to 2011.Aim: The aim of this study was to study how 12-year olds perceive their sound environment in school.Methodology and material: A quantitative questionnaire survey was conducted in the sixth grade at two schools. The questionnaire used included questions from BMHE and self-produced questions. Sixtynine students answered the questionnaire.Results: Over 50 % of the respondents experience annoyance from noise in school several times a week.

Landscape architecture is a visual profession, but other senses also affect our interpretation of a place. Sounds can give us a lot of information about an environment, and they are often perceived as positive. Despite this, research about outdoor sounds most often focus on the reduction of unwanted sounds ? noise ? but the absence of noise does not result in a good soundscape. To accomplish this, sounds we appreciate are needed.

A current conveyor is an active building block that can be used to implement most active and passive components. It differs from the operation amplifier in that it uses current instead of voltage. The current conveyor also has significantly higher voltage gain over a broader frequency range. To simplify the construction of analogue circuits and increase the construction efficiency it is desirable to use a top-down methodology. This means that the whole system is partitioned into a hierarchy of subsystems.

Background: Phonemically balanced word lists are used when obtaining speech recognition scores in noise. These lists are designed for adults, but are still used for children. To properly obtain speech recognition scores in noise for children, normative data is needed to show what differences there are to be expected between children of different ages. Purpose: The main purpose is to obtain normative data for children in the ages of 7, 10 and 13 years for speech recognition scores in noise using words and to compare these with each other and with normative data of adults. A further purpose is to examine if there is any practice- or exhaustion effect to be seen when obtaining speech recognition scores in noise for children in the ages of 7, 10 and 13 years.Material: The participants were ten 7-year-olds, ten 10-year-olds and ten 13-year-olds.

Since the spring 2003 the tenant-owner home association the Terrace in Upplands Väsby municipality lies straight under the approach route to Arlanda Airport?s new third landing chute. Noise levels of over 70 dB have been measured in the area, which exceeds National Board of Housing?s, values for traffic noise at a terrace in connection to housing. By using the method of hedonisk pricing the essay tries to find out if there exists a willingness to pay to reduce the noise in the area.

Constantly growing demands from the costumers in the Automotive industry forces the subcontractors to seek alternative ways to compete. One parameter of quality is the components tolerance against NVH(Noise, Vibraion & Harshness) aspects. Kongsbergs Automotive has developed a new gear shifter platform (Shift-by-Wire) that is sold to Alfa Romeo and used in of their car models. However, the company is not pleased with the components sound quality, therefore the main purpose of this thesis is to develope a number of concepts that is supposed to enhance these NVH-aspects.To get an understanding of the problem an analysis of the causes of the emitted sound has been done parallell to a product decomposition, function decomposition and a Ishikawa-diagram. Together with these methods has a litterature study been performed to get familiar with the physics of an impact and especially the emittment of noise.

There is always a need for more effective ways to store energy in order to reduce the human impact on the environment. One step on the way can be the use of flywheels as kinetic energy storage devices. Low frictional losses are essential for a flywheel to be effective. To minimize these losses active magnetic bearings (AMB) can be used to keep the shaft centered instead of the more conventional ball-bearings. AMBs use actuators and a fast control system that needs correct and noise-free measurement data of the shaft position and the current in the actuators to work properly.This thesis explains the process of constructing power electronics and a current measurement system for active magnetic bearings (AMB).

The public interest in central living in today?s cities has led to an increasing effect of traffic noise pollution, and today 20% of the inhabitants in Sweden suffer from noise a level that exceeds the limits. At the same time the traffic keeps increasing, and recent researches shows that traffic noise pollution and several of today?s most common health issues are connected, for example, reduction of performance, sleeping issues and cardiovascular diseases. For this cause rules, guidelines and environmental goals has been developed, as well as software?s which calculates the levels of pollution, all this to investigate and improve the environment.