Fumiaki Satoh

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.

Comparison between the 1/10‐scale model experiment and the full‐scale measurement in a concert hall

In order to examine the accuracy of acoustic scale modeling, the experimental results of a 1/10‐scale model study performed for acoustical design of a concert hall and those measured in the full‐scale hall after the construction are compared. In the scale model study, the impulse responses were measured by the direct method using a spark discharge source and monaural and binaural microphone systems. For the measurement of the binaural impulse response, a 1/10‐scale dummy head system was made on a trial basis. In the real hall, impulse responses were measured by the sweep‐pulse method using a dodecahedral omnidirectional loudspeaker and monaural and binaural microphone systems. The monaural impulse responses were measured at the corresponding points in the scale model and the real hall, and such quantities as D50, C80, and Ts were obtained and compared. The binaural impulse responses measured in the model and real hall were convolved with the same sources of a variety of music and presented to the subjects...

Acoustical safety as important as comfort and wellness

Needless to say, the points of comfort and wellness are very important for the evaluation of spaces. In addition, how about the point of safety? This doesn’t mean structural safety of buildings or safety to prevent crimes. For example, the luck of intelligibility of evacuation announcement in an emergency, this is an unsafe situation. It’s a matter of “acoustical safety.” To use absorption materials in spaces is very effective on the point of comfort and it leads to be better condition on the point of safety at the same time; however, the point of “acoustical safety” should be emphasized more. In the current situation in Japan, the consideration of using absorption materials for comfortable and safe spaces doesn’t seem to be enough. This is a common understanding in our Japanese researchers on architectural acoustics. Therefore, a committee in Architectural Institute of Japan published a book in order to be popular using absorption materials. In this presentation, the contents about the book and the discussions up to publication will be introduced, in addition to some works on acoustical safety.Needless to say, the points of comfort and wellness are very important for the evaluation of spaces. In addition, how about the point of safety? This doesn’t mean structural safety of buildings or safety to prevent crimes. For example, the luck of intelligibility of evacuation announcement in an emergency, this is an unsafe situation. It’s a matter of “acoustical safety.” To use absorption materials in spaces is very effective on the point of comfort and it leads to be better condition on the point of safety at the same time; however, the point of “acoustical safety” should be emphasized more. In the current situation in Japan, the consideration of using absorption materials for comfortable and safe spaces doesn’t seem to be enough. This is a common understanding in our Japanese researchers on architectural acoustics. Therefore, a committee in Architectural Institute of Japan published a book in order to be popular using absorption materials. In this presentation, the contents about the book and the discu...

Activities of the research committee on education in acoustics in ASJ for children

In the Acoustical Society of Japan (ASJ), the Research Committee on Education in Acoustics was established in 1997. Although its history is relatively short in comparison with the Administrative Committee on Education in Acoustics in the Acoustical Society of America (ASA), many activities have been steadily carried out. For example, surveys of syllabi (educational plans of subjects in universities) were made. Demonstration tools used in university classes were also surveyed. The extent of our research was not limited to only universities. Textbooks and teaching materials used in elementary schools, junior high schools, and senior high schools were also researched. Furthermore, activities in cooperation with the National Museum of Nature and Science in Japan have been taking place, including an exhibition and a class with acoustic demonstrations and handicrafts for children. We believe that such activities are very important as social contributions of an academic society. In this presentation, some of our...

Auralization of municipal public address announcements by applying geometrical sound simulation and multi-channel reproduction techniques

Municipal public address system (M.P.A. system) for disaster prevention is an important system for supplying information outdoors. The speech intelligibility of the M.P.A. system, however, tends to be deteriorated by long-pass-echoes due to reflections from the surrounding buildings and the sounds from the loudspeakers covering other sub-areas. When designing such a M.P.A. system, effective tools for prediction of outdoor sound propagation are needed. For this aim, the authors have been investigating the application of the sound simulation technique based on geometrical acoustics. In addition, auralization is also desirable to subjectively assess the speech intelligibility of the M.P.A. system in acoustical design. Therefore, the authors are developing a simulation technique in which the sounds calculated by the geometrical simulation are reproduced through a 6-channel reproduction system, by which 3D information can be aurally realized. In this paper, the outline of this simulation method and some exampl...

Impulse response measurement in public space using musical signal including swept-sine signals

In design of public spaces, e.g. railway stations, airport terminal buildings and underground shopping centers, careful attention should be paid from an acoustical viewpoint. It is not only for acoustical comfort but also for safety ensured by a public address system with high intelligibility. As a study for this aim, we have been investigating acoustical characteristics of various public spaces. In these studies, it is strongly desired to measure impulse responses in the spaces under live condition with occupants but the usual measurement method using Swept-Sine signals are not applicable because the signals sound very peculiar to the occupants. To mitigate such a problem, we are trying a method using test music signals in which Swept-Sine signals are inserted. In this paper, the availability of this measurement technique is outlined and some measurement results are introduced.

Permissible number of synchronous averaging times to obtain reverberation time from impulse response under time‐variance conditions

In the measurement of room impulse response, the synchronous averaging technique and such new methods as the MLS and the swept‐sine methods are being widely used to improve the signal‐to‐noise ratio. In actual measurement conditions, however, the air in a room is continuously moving and the temperature is changing to some degree. The measured value of the reverberation time in such a room tends to be shorter at higher frequencies when applying the synchronous averaging. Therefore, the assumption of a time invariant has to be carefully considered, and, on this point, some research has been conducted to date. We also have reported various research results concerning the impulse response measurement under the time‐variance conditions. In this paper, the permissible number of synchronous averaging times for reverberation measurement is studied through some field experiments. In each field, many time impulse response measurements were taken between a fixed pair of sound source and receiving positions by the sw...

Influence of time variance on room impulse response measurement

The measurement of room impulse response is made under the assumption that the sound propagation system is time invariant. Actually, however, the air in a room is usually moving and the temperature is changing to a greater or lesser extent. In order to examine the influence of such time variance on the measurement of room impulse response, experimental investigations were performed in a reverberation room in which the air was excited by fans and in a concert hall in which the air‐conditioning system was operated. Impulse response measurements were performed by the maximum‐length sequence (MLS) method and the sweep pulse (SP) method and these results were compared. From the results, it has been found that the reverberation decay tends to become steeper by repeating the impulse response measurement to get high signal‐to‐noise ratio and the SP method is more robust than the MLS method against the influence of time variance of the atmospheric condition in a room.