Kanako Ueno

Effect of room acoustics on musicians' performance. part I: Experimental investigation with a conceptual model

This study aimed to investigate the notion that musicians adjust their performance to suit the acoustics of concert halls. First, a schematic model was developed to provide a basis for the investigation. Second, a performance experiment was conducted: musicians performed under different acoustic conditions simulated in an anechoic room. The performances were recorded, and the musicians were interviewed about the technical details of the adjustments that they made to suit the acoustics. The results showed how expert musicians adapted their performances to the acoustics. Third, as a pilot study to examine if differences could be objectively identified, a listening test and acoustic analysis were conducted on a recorded violin performance. The study confirmed that differences could indeed be objectively identified, at least in terms of the tempo and extent of vibrato.

Recalibration of subjective simultaneity between self-generated movement and delayed auditory feedback.

Temporal contingency between motor commands and corresponding auditory feedback is crucial for perception of self-generated sound as well as external auditory events. The present study examined whether delay detection of self-generated sound was affected by the range of delayed auditory feedback used during the experiment. Participants pressed a button with their right index finger and judged whether auditory feedback was delayed compared with the sensation of finger movement. The range of auditory feedback delay was varied across conditions. To calculate the delay detection threshold (DDT), that is, the point at which the delay detection rate was 50%, we fitted a logistic function to the delay-detection probability curve. The DDT was significantly different across conditions (Tukey–Kramer’s honestly significant difference test, P<0.01). Specifically, the DDT became longer as the mean delay of the range increased. However, this shift was not observed for the delay range with a minimum delay greater than 250 ms. We propose that the subjective simultaneity of auditory feedback and self-body movement is, to some extent, automatically recalibrated toward the mean delay of the delay range used in the experiment.

The effects of spatialized sounds on the sense of presence in auditory virtual environments: A psychological and physiological study

Although many studies have indicated that spatialized sounds increase the subjective sense of presence in virtual environments, few studies have examined the effects of sounds objectively. In this study, we examined whether three-dimensional reproduced sounds increase the sense of presence in auditory virtual environments by using physiological and psychological measures. We presented the sounds of people approaching the listener through a three-dimensional reproduction system using 96 loudspeakers. There were two spatial sound conditions, spatialized and non-spatialized, which had different spatial accuracy of the reproduction. The experimental results showed that presence ratings for spatialized sounds were greater than for non-spatialized sounds. Further, the results of the physiological measures showed that the sympathetic nervous system was activated to a greater extent by the spatialized sounds compared with the non-spatialized sounds, and the responses to the three-dimensional reproduced sounds were similar to those that occur during intrusions into personal space in the real world. Additionally, a correlation was found between the psychological and the physiological responses in the spatialized sound condition. These results suggest that the physiological measures correlate to the perceived presence in acoustic environments.

Neural Basis of the Time Window for Subjective Motor-Auditory Integration

Temporal contiguity between an action and corresponding auditory feedback is crucial to the perception of self-generated sound. However, the neural mechanisms underlying motor–auditory temporal integration are unclear. Here, we conducted four experiments with an oddball paradigm to examine the specific event-related potentials (ERPs) elicited by delayed auditory feedback for a self-generated action. The first experiment confirmed that a pitch-deviant auditory stimulus elicits mismatch negativity (MMN) and P300, both when it is generated passively and by the participant’s action. In our second and third experiments, we investigated the ERP components elicited by delayed auditory feedback for a self-generated action. We found that delayed auditory feedback elicited an enhancement of P2 (enhanced-P2) and a N300 component, which were apparently different from the MMN and P300 components observed in the first experiment. We further investigated the sensitivity of the enhanced-P2 and N300 to delay length in our fourth experiment. Strikingly, the amplitude of the N300 increased as a function of the delay length. Additionally, the N300 amplitude was significantly correlated with the conscious detection of the delay (the 50% detection point was around 200 ms), and hence reduction in the feeling of authorship of the sound (the sense of agency). In contrast, the enhanced-P2 was most prominent in short-delay (≤200 ms) conditions and diminished in long-delay conditions. Our results suggest that different neural mechanisms are employed for the processing of temporally deviant and pitch-deviant auditory feedback. Additionally, the temporal window for subjective motor–auditory integration is likely about 200 ms, as indicated by these auditory ERP components.

Experimental study on applicability of sound masking system in medical examination room

Recently, speech privacy to avoid oral information leakage in healthcare facilities has become an important issue. This study investigated effectiveness of sound masking system in regard to masking efficiency, annoyance and its influence on speech conversation for medical examination rooms in an experimental approach. Considering actual application, two adjacent medical examination rooms partitioned by a low sound insulation wall in a typical healthcare facility were selected as an experimental field and sound masking system was temporally installed. In the rooms, acoustic environment was measured and reproduced in an anechoic room with a 3‐D sound field simulation system using a 6‐ch sound recording/reproduction technique. In the simulated acoustic condition, subjective tests were designed to quantify the masking efficiency and annoyance caused by the masking sound. The annoyance test was conducted in listening condition (with high attention to the sound) and in talking condition (with low attention). As a result, mixed maskers composed by water stream, synthesized speech signals, and steady state noise showed high performance in both aspect of masking efficiency and annoyance.

Motor area activity for action-related and nonaction-related sounds in a three-dimensional sound field reproduction system.

The motor cortical area is often activated to auditory stimuli in the human brain. In this study, we examined whether the motor area shows differential activation for action-related and nonaction-related sounds and whether it is susceptible to the quality of the sounds. A three-dimensional sound field recording and reproduction system based on the boundary surface control principle (BoSC system) was used for this purpose. We measured brain activity during hearing action-related or nonaction-related sounds with electroencephalography using mu rhythm suppression (mu-suppression) as an index of motor cortical activation. The results showed that mu-suppression was observed when the participant heard action-related sounds, but it was not evident when hearing nonaction-related sounds. Moreover, this suppression was significantly larger in the 3D sound field (62-ch loudspeaker condition), which generates a more realistic sound field, than in the 1-ch loudspeaker condition. Our results indicate that the motor area was indeed activated for action-related sounds and that its activation was enhanced with a 3D realistic sound field. We discuss our findings in relation to the mirror neuron system and the possibility of using its activity as an objective measure that reflects the subjective sense of reality in various virtual reality settings when interacting with others.

Subjective evaluation of a virtual acoustic system: Trials with three-dimensional sound field reproduced by the “Sound Cask”

It has been necessary to establish subjective measures for the performance of the virtual acoustic systems. In this paper, we report our trials to evaluate the performance of a three-dimensional sound field reproduction system based on the boundary surface control principle, the “Sound Cask.” First, we introduce our investigations for the experts of audio engineering in order to clarify the difference of auditory impression between the Sound Cask and conventional audio systems. Second, we report psychological and physiological experiments focusing on the advantageous points of the Sound Cask, localization performance, and a clear sense of reality, which were pointed out in the investigations for the experts. Finally, we discuss the issues to be considered for subjective evaluation of virtual acoustic systems for future studies.

The effect of early reflection on players in a concert hall

In order to investigate the effect of hall response on players, field measurements on the stage of a concert hall and laboratory experiment using digital simulation technique were performed. In the field experiment, the subject, a professional violinist, was asked to play and to make comments on her acoustical impression of five points on the stage. As a physical measurement, impulse responses were obtained at the same points by using omni‐directional loudspeakers as a sound source and an omni‐directional microphone and directional microphones as receivers. As a result, it has been found that not only the strength of the early reflections but also their direction influences the subject’s impression. In the laboratory experiment (anechoic chamber), the sound field was modeled and synthesized by using a 13 channel reproduction system; ambient reverberation judged as being natural was provided by simple digital reverberators and different strength and direction of early reflections were obtained by real‐time convolvers. For a constant value of reverberation, several conditions with a different level and direction of the early reflections were created. For each condition, the violin player was asked to make similar judgments as in the field experiment. The results of two experiments were examined.In order to investigate the effect of hall response on players, field measurements on the stage of a concert hall and laboratory experiment using digital simulation technique were performed. In the field experiment, the subject, a professional violinist, was asked to play and to make comments on her acoustical impression of five points on the stage. As a physical measurement, impulse responses were obtained at the same points by using omni‐directional loudspeakers as a sound source and an omni‐directional microphone and directional microphones as receivers. As a result, it has been found that not only the strength of the early reflections but also their direction influences the subject’s impression. In the laboratory experiment (anechoic chamber), the sound field was modeled and synthesized by using a 13 channel reproduction system; ambient reverberation judged as being natural was provided by simple digital reverberators and different strength and direction of early reflections were obtained by real‐time...

Visualization of acoustic resonance phenomena using Kundt’s dust figure method

It is very effective to visualize a sound field for intuitive understanding of various acoustic phenomena, especially for acoustic education. The most famous and classical visualization technique is the Kundt’s dust‐tube method contrived by August Adolph Kundt. He devised this experimental technique to determine the sound velocity in the air by observing the mode pattern of a standing wave excited in a glass tube. The technique can be applied to various other acoustic resonance phenomena. In Japan, Sato and Koyasu applied this technique to a two‐dimensional room acoustic model experiment in which the effect of the shape of a reverberation room on the normal modes was examined. Referring to these experiments, the authors made experimental equipment to visualize acoustic resonance phenomena for an educational purpose. In our experiment, two types of two‐dimensional boxes with hard surface were prepared. In these boxes, normal modes in a closed sound field and the Helmholtz resonance phenomena, which are essential and important for architectural acoustics, can be visualized. These physical experiments are visually impressive on students in architectural courses and therefore the experiment is efficiently used in architectural acoustic courses.

Exciting demonstration in acoustics by high‐school teachers’ group: ‘‘Stray Cats.’’

In Japan, to get students interested in a subject, high‐school teachers often form a group to share their ideas and inventions on education. ‘‘Stray Cats’’ is one of the most active groups in physics. The group has been proposing many exciting demonstrations, which were contrived to support students’ learning process with intuitive understanding of physics. Here, instead of using commercial equipment, they developed simple teaching tools that show physical phenomena in an exciting and attractive way, using quite common materials and daily goods. For example, the velocity of sound is measured by a pipe filled with a gas (air, CO2, helium, etc), setting a loudspeaker and two microphones in the pipe. Interference of sounds is demonstrated by two pipes with attached cone‐shaped horns at one end, which collect a source sound in different phase, and merging them into one at the other end, which produce louder or quieter sound as a result of interference. Hitting or rubbing different length of aluminum rods aids students’ understanding of longitudinal waves and transverse wave with the relationship between rod’s length and pitch, as well as a pleasant experience with beautiful tones. These educational tools will be presented with videos taken with the Stray Cats group.