This paper addresses the challenges in evaluating the structural performance of built structures using non-destructive methods and in situ tests. Such an examination of structural properties, without their sampling, is a diagnostic improvement, especially for historical heritage buildings, where it is not allowed to violate their physical integrity. Therefore, the research proposes a non-destructive testing method based on the equalization of the mechanically and non-destructively determined parameters of the strength of built-in timber. The research included three phases: (1) a preliminary examination; (2) a calibration procedure of the non-destructive method, and (3) in situ application of the established non-destructive method. The preliminary examination involved testing specimens using X-rays and ultrasonic waves by directing them, analogous to mechanical testing, in the fibers’ longitudinal, radial, and tangential directions. In the second phase, it was shown that equalizing the parameters of mechanical and non-destructive testing using ultrasound and X-rays of timber was feasible. Furthermore, mechanical calibration was conducted to establish an applicable non-destructive in situ method. Finally, in the third phase, an in situ assessment of timber architectural elements confirms the effectiveness of the suggested non-destructive approach in diagnosing architectural structures.

The possibility of identifying vibration modes of a double bass bow, with a non-contact measurement of sound pressure in the Very Near Field (VNF) was investigated. This paper shows the application of this cost-effective method for vibroacoustic testings of the bow. The spectra of generated tones do not give sufficient information about a particular bow, but its vibroacoustical behavior provides additional properties. The visualization for all vibration modes below 4000 Hz was achieved by using sound pressure scanning in a VNF. Differences in the vibroacoustical properties of a double bass bow with different hair tension were analyzed.

This study explores non-destructive techniques for characterizing the mechanical properties of materials pertinent to cultural heritage, emphasizing the preservation of sample integrity. A modified acoustic resonance method (MARM), utilizing a two-microphone configuration, is introduced for the simultaneous, fully non-contact determination of dynamic elastic modulus and damping (loss factor). The method is validated through comparison with the impulse excitation technique (IET) and ultrasonic pulse velocity testing (UT). The approach is applied to two material categories exhibiting contrasting porosities: dense natural stone and highly porous unfired clay. Results demonstrate strong concordance among all methods for stone, confirming the reliability of non-destructive techniques for homogeneous materials. Conversely, unfired clay displays greater variability attributable to its heterogeneous and porous nature, alongside increased damping. This investigation reveals that conventional modulus–strength correlations are not directly applicable to unfired clay. To address this, a simplified strength estimation model incorporating the estimated elastic modulus and porosity is proposed. The model achieves improved alignment with experimental data and delineates applicability boundaries for porous materials. The presented framework facilitates consistent, non-destructive evaluation of mechanical properties, with notable implications for the assessment and preservation of cultural heritage materials.

Ovaj rad predstavlja nastavak prethodnih istraživanja o mogućnosti klasifikacije uzoraka zvuka rada motora sa unutrašnjim sagorevanjem u dve različite klase prema tipu pogonskog goriva. Istraživanje uvodi novi pristup koji uključuje mapiranje zvuka u sliku, pri čemu se primenjuje A-ponderisanje uzoraka. Kako A-težinski filtar uobličava signal na sličan način kako se to radi u ljudskom čulu sluha, cilj upotrebe ovog filtra je omogućiti bolje prepoznavanje subjektivnih karakteristika u uzorcima zvuka, čime se generalno unapređuje mogućnost razlikovanja motora prema pogonskom gorivu. Dobijeni rezultati pokazuju da upotreba A-ponderisanih uzoraka značajno poboljšava diferencijaciju između klasa motora (zvuka) na osnovu izraženijih i značajnijih razlika između slika. Povećanje razlika u parametrima zvuka između klasa predstavljaju značajan potencijal za unapređenje tačnosti nadzirane klasifikacije. Obzirom da se koristi klasifikacija koja treba da simulira perceptivno razlikovanje motora, integracija A-ponderisanja u predobradu signala usklađuje pristup primenjenog mašinskog učenja sa ljudskom percepcijom. Rezultati istraživanja ističu efikasnost i potencijal A-ponderisanja uzoraka zvuka pre mapiranju u slike u klasifikacionim algoritmima mašinskog/dubokog učenja,

The first part of this research focuses on characterising the raw material to assess its suitability for production. The second part explores the use of acoustic emission (AE) as a method for monitoring crack formation during the drying process. Numerous experiments are conducted on heavy clay tile samples to identify acoustic emissions related to physical changes in the material during drying. The impulsive nature of the expected acoustic events suggests broadband excitation, while the wet clay itself strongly attenuates higher frequencies. As a result, the main energy is expected to be concentrated in the lower part of the spectrum. The hypothesis that acoustic events associated with the formation of macro- and micro-cracks fall within the audio frequency range is confirmed. As the brick and tile industry is energy-intensive, this approach supports UN Goal 12 by promoting responsible production and reducing drying scrap rate.

The ability to predict behavior of some type of wood as part of a musical instrument is of a great importance. One of the important characteristics of a material, from the standpoint of musical acoustics, is Young's modulus of elasticity, which can be determined by observing the wooden beam test sample response to an excitation. In this process visualization of modes helps pairing frequencies from response spectra with vibration modes of sample, which allows us to numerically calculate Young’s modulus for different frequencies. In this paper, visualization of vibration modes are achieved using the microphone Very Near Field scanning of excited samples.