(especially in the measurement of machines operating in their natural environment, so-called in situ measurements). The 1980s brought the popularization of intensity methods among a wider range of acousticians, resulting in the publication in the 1990s and the first decade of the 21 st century of documents standardizing basic measurement methods involving them [9; 10; 11; 12]. Significantly, they apply only to PP probes. It should also be noted that in 2001 a PU Microflown probe [13] based on [PERSON]'s 1994 invention was placed into production (although, as mentioned, the first information about such a solution appeared about 40 years earlier).  
Intensity methods are of great value both in terms of basic research, where they allow, for example, a detailed analysis of the mechanism of sound generation and absorption by various types of sources and materials and visualization of the acoustic energy distribution around them, e.g., [14; 15; 16]. Among the most important applications of sound intensity measurement are the following:  
1. determining the acoustic power of sources [9; 10; 11; 12; 17; 18; 19];
2. localization of sound sources (direction of arrival (DOA) determination) [19; 20; 21; 22; 23; 24; 25; 26; 27; 28; 29];
3. examination of sound (noise) sources to indicate the mechanism of sound generation [30; 31; 32];
4. measurement of acoustic impedance [33; 34; 35; 36; 37];
5. testing the permeability and acoustic absorptivity of materials [38; 39; 40; 41];
6. visualization of vector acoustic fields and acoustic energy flow [3; 15; 42; 43; 44; 45];
7. study of acoustic energy flow in waveguides and confined areas [46; 47; 48];
8. electro-acoustic transducer examination [49];
9. room acoustics [50; 51].  
As shown above, measuring sound intensity provides valuable information about the sound field that is unavailable when measuring acoustic pressure. However the main motivation for the research undertaken was to show that the need to perform accurate sound intensity measurements is not synonymous with the purchase of a specialized intensity probe, which requires certain financial investments. The paper shows that with classical equipment for pressure field measurements (2D/3D scanning), it is possible, in certain cases, to measure the sound field distribution with a quality comparable to that of costly PP and PU probes using the presented method. The authors' efforts are thus expected to contribute to greater popularity of the method and better results in many fields of applied acoustics. This will make sound intensity measurements more inclusive and no longer restricted to exclusive research centres with specialized equipment.  
In this article, we present a method of sound intensity measurement that (in applications 4-9, at least, listed above) can successfully eliminate the need for specialized and expensive intensity probes and, using only a single microphone, is more affordable and less expensive. It also does not require the specialized calibration characteristic of commercial probes [52; 53]. Compared with previous preliminary studies [49; 54], the purpose of current research was also to quantitatively demonstrate that there is a high agreement of the results obtained when 3D scanning the sound field generated by an electroacoustic transducer (loudspeaker) compared with a commercial PU probe.