This paper outlines an approach for obtaining microphone array geometry for use in traffic noise analysis. The designed array has a smaller number of microphones compared to existing solutions, thereby reducing the cost of system realization. The array geometry is irregular, consists of 24 microphones, and was obtained by an optimization procedure that minimizes beampatterns sidelobes. Microphone position optimization was performed in the frequency band from 300 Hz to 2000 Hz, defined by traffic noise characteristics. The designed array is used in ongoing research dedicated to the analysis of angular distribution of incident traffic noise sound energy impeding a facade in urban environment.

This study presents the analysis of statistical parameters of the output quantisation noise amplitude distribution in the analogue‐to‐digital converter (ADC) with oversampling and decimation. Hypothesis was tested that quantisation noise amplitudes on the output of the system have a Gaussian distribution. To test this hypothesis, Chi‐squared statistical test was performed with parameter estimation based on grouped data. Simulation models were made for two types of ADCs: classical b ‐bit and sigma–delta. Various realisations of decimation filters were used as well as various values of the decimation factor. Based on the number of cases in which the hypothesis was rejected, the significance of the test was determined, i.e. the deviation from the ideal Gaussian distribution was quantified. Results of this research can prove to be useful in system design process, where accurate knowledge of the quantisation noise statistical model parameters is required. This study presents general procedure for analysing the amplitude distribution of the quantisation noise, which can easily be implemented on other modified models of the ADC with oversampling.

Unmanned aerial vehicles open new possibilities for developing technologies that support more sustainable and efficient agriculture. This paper presents a non-invasive method for repelling rodents from crop fields using ultrasound. The proposed system is implemented as a spherical-cap ultrasound loudspeaker array consisting of eight transducers, mounted on a drone that overflies the field while emitting sound in the 20–70 kHz range. The hardware design includes both the loudspeaker array and a custom printed circuit board hosting power amplifiers and a signal generator tailored to drive multiple ultrasonic transducers. In parallel, a genetic algorithm is used to compute flight paths that maximize coverage and increase the probability of driving rodents away from the protected area. As part of the validation phase, artificial intelligence models for rodent detection using a thermal camera are developed to provide quantitative feedback on system performance. The complete prototype is evaluated through a series of experiments conducted both in controlled laboratory conditions and in the field. Field trials highlight which parts of the concept are already effective and identify open challenges that need to be addressed in future work to move from a research prototype toward a deployable product.

This paper examines speech privacy in both residential and commercial spaces. The ASTM E2638 standard defines the Speech Privacy Class (SPC) parameter, which measures speech privacy based on the signal-to-noise ratio at the listener’s position. This paper proposes estimating the SPC value using relevant ISO parameters commonly used in European practice: the apparent sound reduction index in dB (defined by ISO 16283-1, 2 standards) and the equivalent ambient noise level in dBA (defined by the ISO 1996-1 standard). The estimated value of the SPC parameter in this paper is referred to as the Speech Privacy Index (SPI). A diverse range of situations, i.e., rooms, was analyzed in the field. These rooms varied in terms of purpose, organization, dimensions, furnishings, isolation from other spaces, and internal and external environments. The results of the experiments demonstrate a strong correlation between the SPC value estimated according to ISO parameters (the proposed method) and the SPC as defined in the ASTM E standard. This indicates that the proposed method can provide an indicator of the state of speech privacy in buildings. The significance of the proposed calculation method (i.e., the STI parameter) lies in its ability to be applied at the building design stage, as well as after its completion, during routine testing.

Rodents pose a significant threat to agriculture by damaging crops, spreading disease, and contaminating soil. To counter this, farmers often resort to chemical pesticides, which can harm ecosystems, or to non-chemical deterrents that tend to be less effective and subject to rodent adaptation. As a sustainable alternative, the RODENT project, Rodent Obstruction through Drone-Enabled Non-invasive Technology, introduces a dronemounted ultrasound system designed to emit high-frequency signals that deter rodents without harming the environment. In the initial design phase of the project, the first experiments were conducted in anechoic conditions to evaluate the acoustic performance of low-cost ultrasound speakers driven by a custom signal generator and amplifier. Results showed that both attenuation with distance and speaker directivity were within the expected range for rodent-sensitive frequencies, particularly at 70 kHz. However, the presence of side and rear lobes highlighted the need for improved directionality. Obtained results show that the proposed method effectively generates ultrasound signals within the targeted rodent-sensitive frequency range and validates the idea of using low-cost speakers in drone-mounted deterrence systems.

This paper discusses principles of microphone array beamforming, specifically the use of LMS algorithm with training sequence. The problem of wideband nature of acoustical signals and its impact on the techniques of beamforming are discussed. Detailed explanation of classic narrowband and wideband LMS beamformers is presented, as well as the modification of narrowband algorithm with pre-steering. Experimental testing and comparison of algorithm performances was conducted and measurement results are presented. The used microphone array is part of Br?el & Kj?r acoustical camera, and is comprised of 18 omnidirectional non-uniformly spaced microphones.