Sanja Grubeša

Elimination of out-of-band emissions in Digital Radio Mondiale transmissions using the genetic algorithm

When transmitting high-power digital radio Mondiale (DRM) signal from non-linear transmitters, out-of-band emissions are the critical problem since the emitted spectrum does not satisfy spectral mask defined in relevant standards. Several methods have been developed that minimize out-of-band emissions, based on adding spectrally formed impulses to the signal, thus causing high non-selective distortion of modulation characteristics of the digital signal. In order to reduce the amount of those distortions, a new method has been developed for partial elimination of out-of-band emissions by preprocessing signal in digital domain prior to orthogonal frequency-division multiplexing (OFDM) signal construction.

Developing a Model for Assessment of Traffic Distraction

The soundscape of an expressway in Zagreb was recorded and reproduced to two groups of listeners while they were performing a concentration demanding task – a simplified variation of the memory game. This expressway was chosen due to the high traffic frequency and on the other hand, due to the large number of residential buildings that are near the expressway. The focus of the research is whether the residents of a large city, in their daily life have adapted to this noise and how. We also wanted to investigate what is the main reason of their annoyance and distraction. Furthermore, we wanted to quantify human distraction with this typical urban soundscape by developing and then using the acoustic model for total distraction level.

Acoustic Performance of Parallel Baffled Silencers Different Configurations in HVAC Channel

Serious noise pollution is one of the most unwanted consequences of the rapid urbanization and industrialization and various studies have shown that long exposure to noise can result in different health issues. Therefore, the performance of large industrial baffled silencer is crucial for reducing the environmental noise from large industrial plants. In this particular research the acoustic parameters of several different configurations of parallel baffled silencers have been compared by using an in-situ measurement method according to the ISO-11820:1996 Standard. The geometrical parameters e.g. length, thickness and distance between baffles as well as the absorption parameters of baffles have been changed in terms of full absorption and half-absorption surface. Furthermore, their influence on the silencer performance in channel with and without flow has been measured. Transmission and insertion loss acoustic parameters in octave frequency bands from 63 Hz up to 16 kHz are determined in the in-situ measurement setup including the influence of the reflections from baffles at the inlet side and opening at the outlet side. Moreover, the analytical expression ( Piening and trapezoidal equation) for one parallel baffled silencer’s configuration has been compared with the measurement values on octave bands of interest. Additionally, the sound pressure distribution between baffles has also been measured and it can be concluded that the sound pressure level change is much larger at the beginning when compared to the value at the end of a silencer.

Mobile crowdsensing accuracy for noise mapping in smart cities

ABSTRACT This paper deals with the problem of traffic noise in urban areas in terms of noise mapping. It explains in detail the Mobile Crowdsensing (MCS) method and, furthermore, compares the results obtained with this method with the results gained from the standard method that uses a sound level metre. The research done in this paper shows that the MCS method can make noise mapping easier, cheaper and less time-consuming in terms of creating representative noise maps developed on measurements but also noise maps developed on calculations and simulations. The main idea is to show that accuracy and precision of measurements obtained by using calibrated smartphones are acceptable. The paper suggests that when using the smartphone measurement application, the calibration of the measurement chain can be done in free field with class 1 sound level metre, and noise map can be checked in a much larger number of points (in comparison with the standard measurement method) and therefore, smartphones can be used as instruments for creating or even checking final noise maps in urban environment. Another advantage of this method is that citizens can engage in noise monitoring in urban areas and become aware of the noise pollution in their cities.

Air and noise pollution monitoring in the city of Zagreb by using mobile crowdsensing

The rapid progress of urbanization is leading to serious air and noise pollution. Therefore, significant research effort is focused on creating a fine-grained pollution and noise maps to identify urban areas with critical negative impact on human health. The traditional measuring methods typically use expensive and static equipment which is not suitable for dynamic urban environments because of the low spatio-temporal density of measurements. On the other hand, the growing popularity of mobile phones, and their technological capabilities, opens a new perspective on citizen-assisted environmental monitoring. In this paper we present a mobile crowdsensing (MCS) solution for air quality and noise pollution monitoring. More specifically, we show a practical experience of a real-world system deployment, from sensor calibration to data acquisition and analysis. Our initial results indicate a correlation between air and noise pollution with higher values during peak hours due to an increased number of vehicles on the streets.

A comparison between predicted and measured noise levels at the Rijeka ‐ Zagreb motorway

The current calculations used for predicting the levels of road traffic noise can and usually do give results that can differ significantly from the results of measurements of noise levels performed in the field. In order to examine these discrepancies, levels of road traffic noise have been measured on two locations on the Rijeka ‐ Zagreb Motorway. After that, the geographical layout of these locations has been prepared and then input into a computer simulation program with the goal of obtaining simulated road traffic noise levels. Following the assumption that these results will be different, the goal is to determine which of the simulation models used today will provide results that are in the best agreement with the results obtained from the actual field measurements, with the emphasis on this particular geographic region, namely, the Republic of Croatia.

Exciter Architecture for Digital Sound and Video Broadcasting Transmitters

Modern radio-communications have begun the transition process from analog to digital radio-communications and broadcasting. During this transition process, main changes are required in exciter units of transmitters. The architecture of transmitters themselves is the same for both digital and analog broadcasting, but the exciters used for digital broadcasting have to create analog RF exciting signals for the transmitters from the digital data stream. The most common modulation procedure used in digital broadcasting systems is OFDM with QPSK or some kind of QAM keying of sub carriers. Apart from RF signal generation, the exciters are often responsible for control of the whole system, because control data is often included in the digital stream distributed from the broadcast center to the transmitters