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Perception of room mode damping from a musical perspective
(European Acoustics Association, 2024-01-17) Jun, David; Glorieux, Christ; Fišarová, Zuzana; Plášek, Josef; Rychtáriková, Monika
Undamped acoustic modes inside rooms - especially in small ones - are often responsible for a decreased acoustic quality, in particular when the rooms’ main function is ”critical listening” and/or ”playing musical instruments”. Mainly in the latter case, treatment with broadband absorption is not always efficient and yields either uneven or too short reverberation times. Rehearsal rooms are typical cases where the ”liveness” of the space needs to be guaranteed and putting a broadband absorber would make it ”too dry”.Rehearsal room design can be seen as a search for an optimal compromise between sound strength and reverberation time across the audible part of the spectrum. This contribution presents results from listening test experiments, in which the perception of modes was investigated, in particular with respect to what extent differences in axial room mode damping are audible.
Flame spreading across the green roof
(EDP Sciences, 2023-10-30) Hobzová, Klára; Pilinszki, Martin; Skřek, Daniel; Beneš, Petr; Benešová, Romana
The main request for roof exposed to fire is the classification Broof (t3), which prevents the transfer and spread of flame on the surface, this is not required for green roof according to Czech fire standards and regulations. A fire can spread in three ways: direct contact, flying burning particles and thermal radiation. In most cases, the spread of fire between objects occurs with the help of radiation. The article deals with the difference in flame spread over the surface of a green roof during a normal fire without the influence of radiant heat and the Broof (t3) test, where the surface is exposed to radiant heat. The aim was to determine the dependence of flame spread on a flat green roof due to the effect of radiation during a fire and the possibility of endangering neighboring buildings.
Proudění vzduchu v konstrukci crawl space
(Czech Journal of Civil Engineering, 2023-07-20) Pobucká, Slávka; Šuhajda, Karel
Ve střední Evropě je rozšířené zakládání dřevostaveb na základových pasech s podkladním betonem. Zakládání staveb,systémem crawl space,je spíše výjimečné.Tento článek se zabýváprouděnímvzduchu a teplotně vlhkostnímipodmínkamivpřirozeně odvětrávané konstrukci crawl space v Českérepublice. Monitoringkonstrukce probíhal od dubna 2022 do února 2023. Vcrawl space bylo sledováno proudění vzduchu, teplota vzduchu a relativní vlhkost vzduchu. Ve vybraných letních dnech byla takésledována intenzita výměnyvzduchu.Dny byly vybírány za základě průměrné rychlosti proudění venkovního vzduchu. Intenzita větrání vcrawl space během června byla vysoká. Průměrné hodnotyse,ve vybraných dnech, pohybovaly od 5h-1do 12h-1.VČeské republice není ČSN norma, která by se zabývala návrhem konstrukce crawl spacezhlediska odvětrávání.VeSpojenýchstátech amerických jsou uvedeny požadavky vInternational Residential Code (IRC–International Code Council). Při aplikaci této normy bylo zjištěno, že plocha větracích otvorů vesledovanémcrawl space byladvakrát většínež doporučuje International Residential Code
Noise Reduction of Air Distribution Grilles Using 3D Printed Infill Structures
(Studio D - akustika s. r. o., 2023-03-31) Svoboda, David; Berková, Petra; Vlach, František; Bečkovský, David; Gabzdyl, Milan; Deutsch, Martin
The aim of this research is to reduce the noise level of air distribution grilles using 3D printed infill structures. The grilles are installed on a newly developed autonomous ventilation system, which is used for decentralised ventilation of e.g., school classrooms. Several supply and return grilles with functional gyroid and honeycomb shaped infill structures were created and subsequently printed on an FDM 3D printer. Based on measurements and analysis of the maximum sound pressure levels at different microphone positions around the system and at different airflows, the combination of grilles with the greatest noise reduction was selected. The research is complemented by other data such as spectral analysis of the noise, measurement of the airflow velocity through the grilles and measurement of the room reverberation time. Significant noise reduction was achieved by using the proposed grilles and further conclusions were drawn. 3D printing technology proved to be a very useful tool in this case.
Heat Flow through a Facede with a Controlled Ventilated Gap
(MDPI, 2023-03-20) Rubina, Aleš; Uher, Pavel; Vrána, Jakub; Novotný, Miloslav; Nespěšný, Ondřej; Skřek, Daniel; Šuhajdová, Eva; Vystrčil, Jan; Formánek, Marian
The article presents current research results in the field of airflow through a façade with a width of 1 m and a height of 13.7 m and with a ventilated gap, and its effect on the year-round heat balance of this façade. An idea to influence airflow in the ventilated gap of the façade is presented based on the results of developed software and the suitability of closing the air gap in winter and in the transition period of the year is described. First, the boundary conditions of the calculations, which are further used in the energy balance between the interior of the building and the exterior environment are defined. In order to include these influences, a discrete analytical calculation was created. It consists of the time distribution of the investigated thermal phenomena calculations. A significant finding is an obvious benefit of controlling the airflow through a ventilated gap in the winter and especially in the transitional period of the year. This technological knowledge has a high potential for energy savings related to the heating of buildings. As the calculations show, airflow control through a ventilated façade reduces heat flow by 25–30% on average, and in contrast, it increases heat gains by 20% and the specific values are presented within the article.

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