Park, Mun Hum

Now showing 1 - 3 of 3

Some of the metrics are blocked by your
consent settings
Helmholtz resonator coupled with circular membrane
(2024-05-15)
Park, Munhum
;
Toboonchuay, Kajornpop
;
Rattanangkul, Pairoj
The Helmholtz resonator is an old yet highly versatile model of various structures. The conventional form of this resonator with rigid surfaces has been extensively studied, and its characteristics are well understood. In many cases, however, the resonator consists of flexible surfaces that readily respond to the changes in the cavity volume, where recent examples include the base structures for acoustic metamaterials and energy harvesters. In the past, several models, including the two-degree-of-freedom lumped-element models, have been proposed to describe the acousto-mechanical coupling within the membrane-coupled Helmholtz resonator (MCH). However, the predictive scope of the previous models was limited only up to the first two modes of vibration, or they were relatively complicated to implement, offering little insight into the relationship between model parameters and output. In this study, a classic model of the circular membrane fitted to an air-tight cavity was modified and extended to predict the resonance characteristics of the MCH. By solving the equations that describe the transverse wave on the membrane and the motion of the equivalent air mass in the port, a conditioning formula was derived, with which the resonance frequencies could be estimated not only at the first two but also at higher modes of vibration. Moreover, the model was found to provide a unified framework for understanding the resonance characteristics and modal patterns of the three related systems: The circular membrane, the circular membrane with air-tight cavity, and the MCH. When validated in a measurement, the proposed model could reasonably predict the resonance frequencies up to the fifth mode of vibration, above 1.5 kHz, where the prediction accuracy was either comparable to or higher than some previous models.
Some of the metrics are blocked by your
consent settings
Noise in the intensive care unit and its influence on sleep quality: A multicenter observational study in Dutch intensive care units
(2018-10-05)
Simons, Koen S.
;
Verweij, Eva
;
Lemmens, Paul M.C.
;
Jelfs, Sam
;
Park, Munhum
Background: High noise levels in the intensive care unit (ICU) are a well-known problem. Little is known about the effect of noise on sleep quality in ICU patients. The study aim is to determine the effect of noise on subjective sleep quality. Methods: This was a multicenter observational study in six Dutch ICUs. Noise recording equipment was installed in 2-4 rooms per ICU. Adult patients were eligible for the study 48 h after ICU admission and were followed up to maximum of five nights in the ICU. Exclusion criteria were presence of delirium and/or inability to be assessed for sleep quality. Sleep was evaluated using the Richards Campbell Sleep Questionnaire (range 0-100 mm). Noise recordings were used for analysis of various auditory parameters, including the number and duration of restorative periods. Hierarchical mixed model regression analysis was used to determine associations between noise and sleep. Results: In total, 64 patients (68% male), mean age 63.9 (± 11.7) years and mean Acute Physiology And Chronic Health Evaluation (APACHE) II score 21.1 (± 7.1) were included. Average sleep quality score was 56 ± 24 mm. The mean of the 24-h average sound pressure levels (L<inf>Aeq, 24h</inf>) was 54.0 dBA (± 2.4). Mixed-effects regression analyses showed that background noise (β =-0.51, p < 0.05) had a negative impact on sleep quality, whereas number of restorative periods (β = 0.53, p < 0.01) and female sex (β = 1.25, p < 0.01) were weakly but significantly correlated with sleep. Conclusions: Noise levels are negatively associated and restorative periods and female gender are positively associated with subjective sleep quality in ICU patients. Trial registration: Www.ClinicalTrials.gov, NCT01826799. Registered on 9 April 2013.
Some of the metrics are blocked by your
consent settings
Singing in virtual environments: Exploring vocal adaptations to congruent audiovisual scenes of performance venues
(2026-01-05)
Park, Munhum
;
Kittimathaveenan, Kajornsak
This study investigated the vocal adaptations of fifteen soprano singers performing in virtual venues. The virtual reality (VR) system comprised a headphone-based auralization using room impulse responses and a head-mounted display presenting 360-degree still images, both sourced from corresponding real-world venues. Singers performed two songs with differing tempos in each venue, and their audio recordings, captured via a near-lips microphone, were analyzed alongside responses to a comprehensive survey. Results revealed subtle but notable effects of venue: larger spaces were associated with reduced pitch accuracy, brighter timbre, and slower, less pronounced vibrato, while the mid-sized purpose-built auditorium elicited louder singing and greater tremolo extent compared to the excessively dry or reverberant venues. These adaptations primarily occurred at the note level and differed between songs. Interestingly, singers' subjective evaluations often did not align with objective performance metrics, suggesting many of these adjustments were subconscious. The study reveals some subtle impacts of audiovisual scenes on vocal performance and highlights the potential of VR systems for exploring these phenomena. The inclusion of visual cues may have contributed to differences from previous research, warranting further studies on the interplay of audio-visual factors in shaping musical performance.

Park, Mun Hum

Filters

Settings

Sort By

Results per page