@article{MTMT:34518784,
	title = {Further development of rotating beamforming techniques using asynchronous measurements},
	url = {https://m2.mtmt.hu/api/publication/34518784},
	author = {Kocsis, Bálint and Horváth, Csaba},
	doi = {10.1142/S2591728523400066},
	journal-iso = {J THEOR COMPUT ACOUS},
	journal = {Journal of Theoretical and Computational Acoustics},
	volume = {32},
	unique-id = {34518784},
	issn = {2591-7285},
	abstract = {When rotating noise sources, such as turbomachinery, are investigated using phased microphone array measurements and beamforming, sidelobes appear on the resulting beamforming maps. Sidelobes can be decreased by increasing the number of microphones. However, if the investigated phenomenon is steady, then there is a cost-effective alternative: performing asynchronous measurements using phased arrays having a limited number of microphones. The single beamforming maps can be combined in order to arrive at results that are superior in resolution and sidelobe levels. This technique has been investigated in the literature, but according to the authors’ best knowledge, has not yet been applied to turbomachinery. This article introduces a means for applying the asynchronous measurement technique and the combination methods for rotating noise sources. The combination methods are demonstrated on two rotating point sources (both in simulations and measurements), and then on an axial flow fan test case. In the case of the two rotating point sources, the achievable improvement in resolution, average-, and maximum sidelobe levels are shown as compared to the single results. In the case of the axial flow fan, it is demonstrated that the combination methods provide more reliable noise source locations and reveal further noise sources.},
	year = {2024},
	eissn = {2591-7811},
	orcid-numbers = {Horváth, Csaba/0000-0002-5154-9760}
}

@article{MTMT:31831939,
	title = {Experimental and analytical investigation of contra-rotating multi-rotor UAV propeller noise},
	url = {https://m2.mtmt.hu/api/publication/31831939},
	author = {McKay, Ryan S. and Kingan, Michael J. and Go, Sung Tyaek and Jung, Riul},
	doi = {10.1016/j.apacoust.2020.107850},
	journal-iso = {APPL ACOUST},
	journal = {APPLIED ACOUSTICS},
	volume = {177},
	unique-id = {31831939},
	issn = {0003-682X},
	abstract = {Contra-rotating propellers could increase the efficiency and lifting capacity of multi-rotor unmanned aer-ial vehicles (UAVs); however, contra-rotating propellers can produce significant noise levels. This workexperimentally investigated the noise from static contra-rotating UAV propellers in an anechoic chamber.The effects of propeller diameter were studied by testing different configurations of 1200and 1500pro-pellers. The effects of propeller spacing, rotational speed and blade number were also investigated;around 1400 propeller configurations were tested in total. It was observed that interaction tones werea dominant contributor to the overall noise level, which also contained rotor-alone tones and broadbandnoise. A theoretical model for the far-field interaction tone noise produced by a contra-rotating propelleris presented and used to explain the tonal noise levels observed in the experimental results. It was foundthat the tones with a zero azimuthal mode order dominate the noise spectrum close to the propeller axis.It was shown that the amplitude and number of these tones with zero azimuthal mode order could bereduced by using contra-rotating propellers with mismatched blade numbers. It was also experimentallyshown that increased spacing between the propellers generally reduced the amplitude of the interactiontones. The rate of this reduction in amplitude with spacing between the propellers was dependent on fre-quency and spacing. High rates of decay were generally observed at small spacings and lower rates at lar-ger spacings. However, the decay was neither monotonic nor at a uniform rate for all frequencies, whichsuggests that there could be a change in the noise generation mechanism as the spacing increases. Finally,the validity of the indoor static results was demonstrated by comparing the results to an in-flight test of aquadcopter with contra-rotating propellers.},
	year = {2021},
	eissn = {1872-910X}
}