Park, Mun Hum

Preferred name

Park, Mun Hum

Alternative Name

Park, Munhum

Main Affiliation

Music Science and Engineering

munhum.pa@kmitl.ac.th

Now showing 1 - 6 of 6

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The presence of Helmholtz resonance modulates the modes of circular membrane
(2020-08-23)
Toboonchuay, Kajornpop
;
Park, Munhum
A Helmholtz resonator with a circular membrane is a structure that represents a number of real-life systems: For example, kettledrum with hole, the instrument body of Asian spike fiddles (e.g. Thai Saw-u and Cambodian Tro-u), and some acoustic energy harvesters. In the current study, two coupled equations governing the motions of the membrane and that of the air mass in the sound hole were established and solved based on simple assumptions. It was shown that the resonance frequencies corresponding to the circular modes of the membrane were shifted in the presence of the Helmholtz resonator. Furthermore, an additional circular mode could be observed at the frequency lower than the Helmholtz resonance frequency. To validate the theoretical prediction, an experiment was conducted by using a 3D-printed drum, where the frequency response was measured with an impact hammer and a laser doppler vibrometer. It was found that both the additional resonance and the shift in the existing membrane modes could be observed, which agree well with the predicted values.
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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.
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Oral-binaural room impulse responses measured on singers in various halls
(2020-08-23)
Park, Munhum
Oral-binaural room impulse response (OBRIR) refers to the acoustic transfer function from mouth to ears measured in a room, which is useful especially for the evaluation of the stage acoustics from the performers' perspective, where it can also be employed for auralisation. OBRIRs have typically been measured on head and torso simulators, whereas the measurement on human was considered to be difficult, for example, for the limited spectrum of the human-generated source sound and for the variance of the data in the course of a long measurement time. Recently, a method was proposed to effectively measure the OBRIRs on singers where singing major scales within 1~2 minutes was found to be sufficient to produce usable transfer functions. In the current study, OBRIRs were measured by using this method on volunteer singers in a few performance spaces with varying size. As expected, the OBRIRs differed between singers, where the impulse responses after the arrival of the direct sound heavily depended on the acoustic properties of the room. The singer's position and orientation on the stage and the type of vowel pronounced for the measurement were also shown to modulate the OBRIRs.
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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.
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Exploring the effects of room acoustics on soprano singers’ vocal performance in three virtual venues
(2024-01-01)
Park, Munhum
;
Kittimathaveenan, Kajornsak
In previous research, efforts have been made to understand the relationship between acoustic attributes of performance spaces and subjective/objective assessments of musicians’ performances. While some studies suggested a correlation between performance or note duration and reverberation time, prior findings have been inconsistent and often lacked statistical significance, primarily due to experimental design constraints or small sample sizes. In this study, 15 soprano singers participated in a series of repeated performances of two songs in three virtual venues simulated by using a real-time auralization system with a head-mounted display. Close-up recordings of the singers’ performances were analyzed, extracting various audio features for comparison across venues with reverberation times ranging from approximately 0.3 to 3.5 seconds. Results from repeated-measure ANOVA indicated that: 1) there was a marginal increase in rest duration with higher reverberation time, albeit statistically insignificant; 2) singers exhibited slightly louder and more resonant performances in a purpose-built music hall compared to smaller/larger venues; 3) increased reverberation seemed to correlate with decreased pitch accuracy and reduced use of vibrato and tremolo in certain notes. Future research aims to explore the interaction between venue characteristics and musical repertoire in more detail.
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The influence of stage acoustics on the singers’ performance and perception: A pilot study
(2021-01-01)
Kittimathaveenan, Kajornsak
;
Park, Munhum
It is known that musicians tend to adjust their performance to the acoustical properties of the hall as they perceive. In a large reverberant hall, for example, they may play staccato notes even shorter than they would in a less reverberant hall to make the music more clearly understandable by the audience. In this study, four singers were invited to sing two (slow and fast) pieces of music in three venues, of which the reverberation times were 0.3, 1.8, and 3.4 seconds. Singers were surveyed with questions regarding the tempo, intonation, resonance and diction of their performance in each venue. Also, the singing voice was recorded by using a headset microphone and analyzed to relate the audio features to the characteristics of the venues. The results showed that the singers’ perception of the vocal resonance was significantly related to the venue (p = 0.024), and so were the average sound level and the dynamic range of the sound level (p = 0.040 for both dependent variables), which could partly be explained in relation to the reverberation time.

Park, Mun Hum

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