The concept of energy harvesting is a mechanism of deriving energy from the sources present in the environment. Using this energy will enable wireless and portable electronic devices to be completely self-sustaining. The sources of energy available for harvesting can be put into the following types: electromagnetic radiation,  vibration-, sound -, and wind- energy. The output power levels from these sources and the mechanism involved in energy conversion decided on the possibility of using it.

The paper analyses the variability of the acoustical energy generated by traffic volume. This energy is  correlated to second power of acoustical pressure. The acoustical pressure was calculated after sound level measurements recorded by permanent automatic sound and traffic volume monitoring stations in Kielce. The city of Kielce was selected as an example of a medium-sized city located in the southern part of central Poland. The measurements were carried out 24 hours a day. The RMS values based on A-weighted sound level were recorded every 1 s in the buffer and the results were registered every 1 min over the period of investigations.The equivalent sound level was calculated on this basis for three time intervals, i.e., from 6:00 to 18:00, from 18:00 to 22:00 and from 22:00 to 6:00. In this study, the authors analysed the acoustical energy expressed in terms of Pa2 to be able to compare the fixed components (the mean and the median) and variable components (deviation from the mean). This paper reports the results calculated for all days of the week, split into three time sub-intervals (night time, day time and evenings). The standard deviation, coefficient of variation, the positional coefficient of variation, the quartile deviation and was proposed for performing a comparative analysis of the acoustical energy scattering.

The agreement of the distribution of the variable under analysis with normal distribution was evaluated.The Shapiro-Wilk test and the Jarque-Bera test provided sufficient evidence to reject the null hypothesis about normal distribution of the data under analysis at the assumed significance level of 0.05. The coefficient of variation is a parameter that satisfactorily describes a variable component of an acoustic energy. This coefficient is suitable for analysing deviations of the variable from its mean. The use of the median for determining coefficients of variation seems to be an option worth considering.

Uncertainties of the acoustical energy calculations were compared within the periods under analysis. The investigations indicated that the analysed data varied depending on the day of the week and time intervals. The differences concerned the values of uncertainties and coefficients of variation of the acoustical energy as well.