Publications by authors named "Jer-Ming Chen"

8 Publications

  • Page 1 of 1

Acoustic Effect of Face Mask Design and Material Choice.

Acoust Aust 2021 Jun 3:1-8. Epub 2021 Jun 3.

Singapore University of Technology and Design, 8 Somapah Rd, Singapore, Singapore.

The widespread adoption of face masks is now a standard public health response to the 2020 pandemic. Although studies have shown that wearing a face mask interferes with speech and intelligibility, relating the acoustic response of the mask to design parameters such as fabric choice, number of layers and mask geometry is not well understood. Using a dummy head mounted with a loudspeaker at its mouth generating a broadband signal, we report the acoustic response associated with 10 different masks (different material/design) and the effect of material layers; a small number of masks were found to be almost acoustically transparent (minimal losses). While different mask material and design result in different frequency responses, we find that material selection has somewhat greater influence on transmission characteristics than mask design or geometry choices.

Supplementary Information: The online version contains supplementary material available at 10.1007/s40857-021-00245-2.
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http://dx.doi.org/10.1007/s40857-021-00245-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8172558PMC
June 2021

Asthmatic versus healthy child classification based on cough and vocalised /ɑ:/ sounds.

J Acoust Soc Am 2020 09;148(3):EL253

Singapore University of Technology and Design, Singapore, Singapore.

Cough is a common symptom presenting in asthmatic children. In this investigation, an audio-based classification model is presented that can differentiate between healthy and asthmatic children, based on the combination of cough and vocalised /ɑ:/ sounds. A Gaussian mixture model using mel-frequency cepstral coefficients and constant-Q cepstral coefficients was trained. When comparing the predicted labels with the clinician's diagnosis, this cough sound model reaches an overall accuracy of 95.3%. The vocalised /ɑ:/ model reaches an accuracy of 72.2%, which is still significant because the dataset contains only 333 /ɑ:/ sounds versus 2029 cough sounds.
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http://dx.doi.org/10.1121/10.0001933DOI Listing
September 2020

Perceptual evaluation of measures of spectral variance.

J Acoust Soc Am 2018 06;143(6):3300

Department of Information Systems Technology and Design, Singapore University of Technology and Design, 8 Somapah Road, Singapore 487372, Singapore.

In many applications, it is desirable to achieve a signal that is as close as possible to ideal white noise. One example is in the design of an artificial reverberator, whereby there is a need for its lossless prototype output from an impulse input to be perceptually white as much as possible. The Ljung-Box test, the Drouiche test, and the Wiener Entropy-also called the Spectral Flatness Measure-are three well-known methods for quantifying the similarity of a given signal to ideal white noise. In this paper, listening tests are conducted to measure the Just Noticeable Difference (JND) on the perception of white noise, which is the JND between ideal Gaussian white noise and noise with a specified deviation from the flat spectrum. This paper reports the JND values using one of these measures of whiteness, which is the Ljung-Box test. This paper finds considerable disagreement between the Ljung-Box test and the other two methods and shows that none of the methods is a significantly better predictor of listeners' perception of whiteness. This suggests a need for a whiteness test that is more closely correlated to human perception.
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http://dx.doi.org/10.1121/1.5040484DOI Listing
June 2018

The effect of nearby timpani strokes on horn playing.

J Acoust Soc Am 2014 Jan;135(1):472-8

School of Physics, The University of New South Wales, Sydney New South Wales 2052, Australia.

Horn players have observed that timpani strokes can interfere disruptively with their playing, especially when they are seated close to the timpani. Measuring the horn's transfer function in the bell-to-mouthpiece direction reveals that the horn behaves as an acoustic impedance matching device, capable of transmitting waves with pressure gains of at least 20 dB near horn playing resonances. During moderate to loud timpani strokes, the horn transmits an overall impulse gain response of at least 16 dB from the bell to the mouthpiece, while evidence of non-linear bore propagation can be observed for louder strokes. If the timpani is tuned near a horn resonance, as is usually the case, further bore resonance interactions may be observed leading to gains of ∼26 dB from bell to mouthpiece. Finally, measurements of horn playing made under conditions approximating playing reveal that timpani strokes sounding near the horn bell are capable of disrupting horn playing by affecting the amplitude, periodicity, and frequency of the pressure signal generated at the horn player's lips.
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http://dx.doi.org/10.1121/1.4829533DOI Listing
January 2014

Do trumpet players tune resonances of the vocal tract?

J Acoust Soc Am 2012 Jan;131(1):722-7

School of Physics, The University of New South Wales, Sydney, NSW 2052, Australia.

The acoustic impedance spectrum was measured in the mouths of seven trumpeters while they played normal notes and while they practiced "bending" the pitch below or above the normal value. The peaks in vocal tract impedance usually had magnitudes rather smaller than those of the bore of the trumpet. Over the range measured, none of the trumpeters showed systematic tuning of the resonances of the vocal tract. However, all players commented that the presence of the impedance head in the mouth prevented them from playing the very highest notes of which they were normally capable. It is therefore possible that these players might use either resonance tuning or perhaps very high impedance magnitudes for some notes beyond the measured range. The observed lack of tuning contrasts with measurements for the saxophone which, like the trumpet, has weak resonances in the third and fourth octaves. Saxophonists are only able to play the highest range by tuning resonances of the vocal tract, so that the series impedance has a very strong peak at a frequency near that of the desired note. This difference is explained by the greater control that the trumpet player has over the natural frequency of the vibrating valve.
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http://dx.doi.org/10.1121/1.3651241DOI Listing
January 2012

Saxophonists tune vocal tract resonances in advanced performance techniques.

J Acoust Soc Am 2011 Jan;129(1):415-26

School of Physics, The University of New South Wales, Sydney, New South Wales, 2052, Australia.

The acoustical impedance spectrum was measured in the mouths of saxophonists while they played. During bugling and while playing in the very high or altissimo range, experienced players tune a strong, but relatively broad, peak in the tract impedance to select which peak in the bore impedance will determine the note. Less experienced players are unable to produce resonances with impedance peaks comparable in magnitude to those of the bore and consequently are unable to play these notes. Experienced players can also tune their tracts to select which combinations of notes are played simultaneously in multiphonics or chords, and to produce pitch bending, a technique in which notes are produced at frequencies far from those of the peak of impedance of the instrument bore. However, in normal playing in the standard range, there is no consistent tuning of the tract resonances. The playing frequency, in all cases, lies close to the peak in the impedance of the reed in parallel with the series combination of the impedances measured in the mouth and the instrument bore on either side of the reed (ZMouth+ZBore)∥ZReed.
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http://dx.doi.org/10.1121/1.3514423DOI Listing
January 2011

Pitch bending and glissandi on the clarinet: roles of the vocal tract and partial tone hole closure.

J Acoust Soc Am 2009 Sep;126(3):1511-20

School of Physics, The University of New South Wales, Sydney, NSW 2052, Australia.

Clarinettists combine non-standard fingerings with particular vocal tract configurations to achieve pitch bending, i.e., sounding pitches that can deviate substantially from those of standard fingerings. Impedance spectra were measured in the mouth of expert clarinettists while they played normally and during pitch bending, using a measurement head incorporated within a functioning clarinet mouthpiece. These were compared with the input impedance spectra of the clarinet for the fingerings used. Partially uncovering a tone hole by sliding a finger raises the frequency of clarinet impedance peaks, thereby allowing smooth increases in sounding pitch over some of the range. To bend notes in the second register and higher, however, clarinettists produce vocal tract resonances whose impedance maxima have magnitudes comparable with those of the bore resonance, which then may influence or determine the sounding frequency. It is much easier to bend notes down than up because of the phase relations of the bore and tract resonances, and the compliance of the reed. Expert clarinettists performed the glissando opening of Gershwin's 'Rhapsody in Blue'. Here, players coordinate the two effects: They slide their fingers gradually over open tone holes, while simultaneously adjusting a strong vocal tract resonance to the desired pitch.
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http://dx.doi.org/10.1121/1.3177269DOI Listing
September 2009

Experienced saxophonists learn to tune their vocal tracts.

Science 2008 Feb;319(5864):776

School of Physics, University of New South Wales, Sydney, NSW 2052, Australia.

Acousticians have long debated whether and how the resonances of the vocal tract are involved in the playing of clarinet and saxophone. We measured the resonances of saxophonists' vocal tracts directly while they played. Over most of the instrument's range, there is no simple relation between tract resonances and the note played, and the tract resonances varied among players. In the high (altissimo) range, a strong resonance of the tracts of professional saxophonists was systematically tuned slightly above the desired note. Amateurs, who did not tune a strong resonance, were unable to play notes in the altissimo range.
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http://dx.doi.org/10.1126/science.1151411DOI Listing
February 2008
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