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 - 10 of 11

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Measurement of oral-binaural room impulse response by singing scales
(2019-01-01)
Park, Munhum
Oral-binaural room impulse responses (OBRIRs) are the transfer functions from mouth to ears measured in a room. Modulated by many factors, OBRIRs contain information for the study of stage acoustics from the performer’s perspective and can be used for the auralization. Measuring OBRIRs on human is, however, a cumbersome and time-consuming process. In the current study, some issues of the OBRIR measurement on human were addressed in a series of measurement. With in-ear and mouth microphones, volunteers sang scales, and a simple post-processing scheme was used to refine the transfer functions. The results suggest that OBRIRs may be measured consistently by using the proposed protocol, where only 4~8 diatonic scales need to be sung depending on the target signal-to-noise ratio.
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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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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.
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Verweij, Eva
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Lemmens, Paul M.C.
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Jelfs, Sam
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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.
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A preliminary analysis of the sources of noise in an open-plan neonatal intensive care unit
(2017-01-01)
Park, Munhum
;
Vermeulen, Ronald
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Laroche, Sabine
;
Gillies, Murray
The acoustic environment in neonatal intensive care units (NICUs) is known to be hardly conducive to the treatment and development of preterm infants. Many studies report the results of acoustic surveys in NICUs, where some studies also investigated the sources of noise. These studies employed a human observer to annotate the noise sources on site, which unfortunately makes the results vulnerable to the Hawthorn effect. Furthermore, most noise source surveys were carried out for a few hours at particular times of day, thus revealing only part of the complete situation. To overcome the shortcomings of the previous studies, the noise sources in an open-plan NICU were investigated in the current study by an offline annotation of 24-hour continuous audio recordings made inside and above an incubator. The results showed that a total of 17 noise sources could be identified in 30159 intervals that occupied 22.1/24 hours, where up to 7 concurrent sound events were present in each interval. The events produced by staff and non-patients’ activities (excluding speech) were counted most frequently, 12878 times, and the alarms from life-supporting/-monitoring devices were present for the longest accumulated duration, 19.5/24 hours. Noise level data were also extracted from the calibrated recordings and analyzed in synchrony with the annotation results. The results showed that the strongest noise source was the patient’s own noise (e.g., crying) inside the incubator and the other patients’ noise above the incubator. Excluding the patient’s own noise, the alarms and the non-patients’ activity noises contributed to the total acoustic energy inside the incubator by 43% and 42% and above the incubator by 53% and 26%, respectively. It is suggested that a better management of alarm systems and an appropriate staff education may improve the acoustic environment in NICUs.
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Analysis of warning sounds used in public transportation systems
(2017-01-01)
Chuprasert, Pavarit
;
Phupantachsee, Nawasch
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Park, Munhum
For the safety of passengers, warning sounds are used in public transportation services, for example, when the train doors are closed. Although the audibility of these sounds is normally required and must be regulated by transportation authorities, the associated noise levels are often unnecessarily high, which frequently lead to the passengers’ discomfort and complaints. In this study, we investigated the door-closing sounds used in the Bangkok Mass Transit System (BTS) Skytrain by evaluating the noise levels and spectral characteristics. The maximum A-weighted sound pressure level (L<inf>AFmax</inf>) was repeatedly measured at 7 representative positions within each car for two types of train, which differed in terms of the location of loudspeakers. The range of L<inf>AFmax</inf> was found to be 67.4 dBA to 97.2 dBA with the median at 77.1 dBA, and the train type was found to significantly influence the noise level (p=0.006), and so was the location in train car (p<0.001). The spectral analysis revealed that the door-closing warning sounds consisted of strong ~3-kHz tone bursts (with a few harmonics), which were found to be 15~20 dBA above the ambient level. The outcome of the study suggests that the warning sounds used in the BTS Skytrain are likely to distress the passengers due to the excessive playback level and the tonality. Further discussions are made on methods to reduce the psychological impact of the warning sounds on passengers while maintaining a good audibility.
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The effect of "Twinkle Twinkle Little Star" on short-term memory
(2018-01-01)
Park, Munhum
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Chuprasert, Pavarit
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Kloemwilai, Achcharaphan
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Fahkrajang, Napat
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Sawetratanastien, Pruch
Irrelevant speech effect (ISE) refers to the decrease in cognitive performance under the influence of a sound which is not related to the task. Typically, ISE has been quantified for speech noise by the rate of errors in recalling visually presented items (serial-recall task). Despite the limited effect size, non-speech sounds have also been shown to disrupt the short-term memory in serial-recall task, of which the spectro-temporal characteristics may easily be adjusted to investigate some aspects of ISE. In the current study, a well-known tune ‘Twinkle Twinkle Little Star’ was used to create a set of stimuli that differed in three factors: 1) Instrument type (played either on a MIDI piano or in pure tones); 2) number of notes per second (two or four); 3) playing order (original, reverse or random). The results showed some trends that the piano sound disrupts the task slightly more than the pure tone, and so does the four-note version than the two-note. When played in a random order, the error rate was higher than the original-/reverse-order versions, whereas the latter two conditions were almost equal. These trends may be explained in relation to the temporal and spectral variations between sound tokens.
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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.

Park, Mun Hum

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