Acoustic Parameters Pendopo Mangkunegaran Surakarta for Javanese Gamelan Performance

Transcription

1 Arte-Polis 5 Intl Conference Reflections on Creativity: Public Engagement and the Making of Place 1 Acoustic Parameters Pendopo Mangkunegaran Surakarta for Javanese Gamelan Performance SUYATNO Doctoral Student - Department of Engineering Physics, Institut Teknologi Bandung Lecturer - Department of Physics of Institut Teknologi Sepuluh Nopember Surabaya kangyatno@physics.its.ac.id Prof. H. A. TJOKRONEGORO Lecturer - Department of Engineering Physics Institut Teknologi Bandung DR. IGN. MERTHAYASA Lecturer - Department of Engineering Physics Institut Teknologi Bandung Prof. R. SUPANGGAH Lecturer - Department of Karawitan ISI Surakarta ABSTRACT Architecturally, the shape of Pendopo Mangkunegaran Surakarta has a pyramid shape without wall. It s volume is 3000 m 3. The ceiling is made from painted wood with a slope of 20 o. The outside of Pendopo has a barrier of a rigid wall which reduce a background noise. As a semi-open concert halls, the ceiling architecture of Pendopo Mangkunegaran Surakarta has an important role as a reflector and guidance of sound to the audience. The Objective of the research reported in this paper are to find out the condition of Listening Level (LL), sub-sequence Reverberation Time (T sub ) and Inter-Aural Cross Correlation (IACC) at Pendopo Mangkunegaran Surakarta. To measure the acoustics parameters of Pendopo, microphones were placed at the area of the King Place, the Guests Place, dancers and audience with a sound source at the corner of the where the Gamelan is played. From the measurement, the Pendopo have a background noise of 54 dba, sub-sequent reverberation time are in the range of 1.2 s 2.2 s and the IACC are The sound source was set in the position where the Gamelan reside, which is in a corner of the room, produces diverse distribution of sound and reverberation time in the room, especially in the center of the room. As a result, the sound generated by Gamelan, for particular show, results an energy that is very strong up to 90 dba at the stage and 71 dba at the farthest point (40 m from the stage). Therefore, the Pendopo Mangkunegaran is suitable to meet the acoustic characteristics of Javanese Gamelan, with a well-developed spatial effect. Keyword: Javanese Gamelan, acoustics parameters, semi-open concert hall, Pendopo Mangkunegaran, listening level, reverberation time, inter aural cross correlation

2 Arte-Polis 5 Intl Conference Reflections on Creativity: Public Engagement and the Making of Place 2 INTRODUCTION Javanese Gamelan is set of traditional music that developing since hundreds years ago. Javanese Gamelan traditionally is performed in the main hall of Palace called Pendopo. Historically, Gamelan java is a part of a communication means when the King want to give a kind of message as well as when the King want to hear the people wishes. That is, in the progress of traditional music and song played by Javanese Gamelan, voices come from attendances may become part of the performance. Javanese Gamelan has range of frequency of 40 Hz to 4000 Hz and sound envelope up to 10 s or greater (Suyatno, 2013). In closed room, the Javanese Gamelan performance can produce an excessive reverberation (Supanggah, 2002). That is the reason Javanese Gamelan performance is almost played at the open or semi-open hall. Javanese Gamelan consists of number of instruments forms an ensamble called as Gamelan. Layout of the instruments of the Javanese Gamelan on stage results different response received by the listener depends on the distance and position to the listener. Among the importance is the difference of listening level received by the left and right ears (IACC / Inter Aural Cross Correlation). The value of IACC also shows diffusivity of space and sound distribution that affected to the stereo effect of room (Ando, 1998). According the Sabine formula (Schroder, 2007), a representative acoustics parameter of a room is reverberation time (RT). Reverberation time is the time it takes the sound to decay by 60 db since the sound source is turned off. The value of RT represents the sound absorption occurs at the room that depends on volume and total absorption of the room (α). Theoretically, the value of RT is a single value that owned by a room and not depends on position. While in real terms, the value of the reverberation time is different at every position that called sub-sequences reverberation time (T sub ). T sub values obtained based on impulse responses and depend on position. There are other parameters characterize the acoustic condition of a room: a. volume of the room b. background noise c. material properties in the room d. the shape and model of the room Among the four parameters above, as mentioned, in some Javanese Gamelan performances, the noise like sounds come from attendances around of Pendopo was a part of the show itself. However, the clarity of the sound is still required by any player as a prerequisite to be able to function properly (Supanggah, 2002). Clarity (C 80 ) and Definition (D 50 ) are also parameters that associated with the RT (Campanini, 2009) Clarity is logarithmic value from ratio of the early energy at 0-80 ms to reverberant energy (80 ms - end). While the definition is defined as the ratio of the sound energy in the first 50 ms to the total energy (0 - end). The optimum values of the acoustics parameters for classical music concert hall are 1.30 s to 1.83 s for RT, -2 db to +4 db for C 80, and 45% to 65% for D 50 (Riberio, 2003). On the other hands, based on simulation, for room acoustics parameters for Javanese Gamelan are s to s for RT, 75 db up to 77 db for LL (Sarwono, 2001, 2002).

3 Arte-Polis 5 Intl Conference Reflections on Creativity: Public Engagement and the Making of Place 3 Pendopo Mangkunegaran Surakarta As mentioned early, traditionally in the past the function of Pendopo (the Pendopo Mangkenegaran as well) is as a Palace for the King and also a center of communication between King and their People. At Pendopo the King meets their people, does socialization and interaction with public to deliver messages to the public. The message conveyed to the public very often in the form of art music and dance performed by the gamelan. By the tradition, the Pendopo become a culture center, were developed many kind of Javanese song and art music, a kind of pride culture of the nation. Through the interaction, it has produced the works of art and culture that became a pride of the nation. At present, the function of Pendopo Mangkunegaran Surakarta almost as a center of Javanese art culture. For example, in certain days, a Javanese Gamelan performance may be enjoyed directly by public (musical, dance and Javanese puppet called Wayang ). Figure 1 shows the architectural shape and position of Pendopo Mangkunegaran Surakarta. (a) (b) Pringgitan Terrace Main of Pendopo Terrace Front (c) Figure 1. Architectural Shape of Pendopo Mangkunegaran Surakarta (a) Outside of Main Pendopo Mangkunegaran (b) Situation in the room of Pendopo Mangkunegaran (c). Position of Pendopo Under these conditions, any place in the Pendopo Mangkunegaran have a significance conjunction with parameters of audio and visual, especially the King place and gamelan. To support the functions of the Pendopo as socialization and interaction with the public, the voice should be heard clearly from all directions, so that the listening level and clarity of sound is very important parameters.

4 Arte-Polis 5 Intl Conference Reflections on Creativity: Public Engagement and the Making of Place 4 By considering Pendopo Mangkunegaran as a concert hall, this paper will discuss its acoustic parameters i.e. LL, T sub, Clarity (C 80, D 50 ) and IACC at the audience area. These parameters are calculated from the measurement at certain points in the audience area. The calculation was made by two approaches. First approach using an impulse response and the second by analyzing the responses to the Javanese Gamelan live performances. Parameters obtained can be used as a guide in designing enclosed concert hall for Javanese Gamelan has a preference as a semiopen room where the artwork was created. MEASUREMENT As a semi-open hall, sound reflection and diffusion in Pendopo Mangkunegaran is caused by the ceiling and the floor. Consequently, the acoustic parameters (sound response) are not homogeny in the space of listener. Each position has its own parameter, such as distribution of the sound (LL), Sub-sequent reverberation time (T sub ), clarity and IACC. To determine the distribution of the sound, the sound measurements are obtained from certain positions at the area of dancers and audience. To obtain the LL, T sub, C 50 and D 80, the white noise and the impulse are used as a sound source that are placed in one corner of the room, the position of the Javanese Gamelan performed. The microphones are placed at King place, guests place, dancer area and public area. The height is 1.2 m for the audience area (the King and people) and 1.5 m for the dancer position. Whereas, particularly, the IACC values are obtained from live performances a Javanese Gamelan with the Javanese music composition of Ketawang Puspowarno. The Position of microphones for IACC measurement is at the left and right of ear audience facing dancer s area. Figure 2 shows the position of microphones at Pendopo Mangkunegaran. Figure 2. Microphone position for measurement at Pendopo Mangkunegaran (a) Sub-sequent Reverberation Time, (b) IACC The signals were recorded at sampling frequency of Hz. The recorded signal then were analyzed by sound analyzer with integral time is 1 s and running step is 0.01 s.

5 Arte-Polis 5 Intl Conference Reflections on Creativity: Public Engagement and the Making of Place 5 RESULT AND DISCUSSION Position of Pendopo Mangkunegaran that surrounded by buildings makes the noise level in Pendopo is 54 dba, 62 dba at the terrace and 70 dba at the outside of Pendopo. However, the buildings around the Pendopo also serve as sound reflector that makes reverberation around the Pendopo. As a semi-open hall that has no wall around, with a volume of 3000 m 3 and the floor surface of 1080 m 2, Pendopo has sound energy decay is quite fast. But the shape and slope of the ceiling make sound reflection and diffusion such that the energy reverberation and energy distribution (LL) are quite enough for audience without a supporting amplifier (sound system). Figure 3. shows an illustration of the reflection of sound that occurs at the Pendopo Mangkunegaran Surakarta. Cavity Reflection Reflection Direct Source Direct Receiver Figure 3. Sound Propagations at the Pendopo Mangkunegaran Figure 3 shows the sound propagation at Pendopo Mangkunegaran from the source to audiences, where the source is produced by the Javanese Gamelan located at the corner of Pendopo (Figure 2). At the audience area, the sound received by audience is combination of direct sound and reflection components from the ceiling. In a particular performance, the listening levels that produced by Javanese Gamelan instruments on stage is 98 db or greater, depend on the music composition and the aim of the show performed (Suyatno, 2013). Because of the ceiling effects, the value of LL at the farthest position in main Pendopo, 40 m from the source is 71 dba, is 90 dba. Because the position of listener was different (spread), the listening level and direction of the sound received by the listener is also different. The acoustic parameters which are taken into account to determine the direction of the sound is IACC. IACC is the acoustic parameter that considers the direction of the sound source based on differences in responses (LL) received by the left and right ear. The values of IACC and T sub at Pendopo Mangkunegaran as shown in Figure 4.

6 Arte-Polis 5 Intl Conference Reflections on Creativity: Public Engagement and the Making of Place Front Front source (a) source (b) Figure 4. Distribution of acoustic parameter (a) T sub (s), (b) IACC Figure 4 (a) shows the T sub at the Pendopo Mangkunegaran has value of 1.3 to 2.2 s. The value was resulted by the shape of ceiling and the reflective material. Value of T sub at the center of room (position of the dancer) is the heights equal to 2.2 s. This value was resulted by the reflection from the horizontal ceiling and staircase at the center and also by the cavity on top of ceiling. While value for T sub is at the entrance to the Pendopo is the lowest that is equal to 1.3 s. This position is directly coupled to outside of the Pendopo, so the reflections that come are not very significant. While, the position of the King has a value of T sub is 1.6 s. This value actually is average of the overall values of the T sub at Pendopo. The shape and reflective properties of ceiling materials cause the sound reflections energy in the room is quite strong. In turn, this makes the sound distribution and reverberation in the room significantly influences to the sound clarity (speech and music). The value of clarity parameter (C 80 ) at the Pendopo Mangkunegaran is +2 db, while the value of definition (D 50 ) is 54%. This means that reverberant energy is smaller than the early energy, so that the signal (music) can be heard clearly (C 80 =+2 db), and so do the vocal (D 50 =54%). Figure 4 (a) shows Pendopo Mangkunegaran has IACC from 0.22 s to 0.71 s. The highest IACC is in front of the stage. This means that the audience received the direct component more dominant than the reflected component. At the place of The King has the value of IACC equals to This means the place of the King has a good stereo effect. While at the position of the dancer the value of IACC is 0.64, which means at this position the direct component is more dominant. This property is important for the dancers to be harmony according to the music performance. CONCLUSION As a semi-open hall, the geographical position with respect to the environment and the architectural shape of the Pendopo Mangkunegaran result a background noise of 54 dba. However, at the outside of Pendopo (terrace) the background noise is 62 dba and at outside the building is 70 dba.

7 Arte-Polis 5 Intl Conference Reflections on Creativity: Public Engagement and the Making of Place 7 The sound reflection produced by the ceiling and the floor result the LL of Pendopo is strong enough. At the farthest distance (at 40 m) the LL is 71 dba with respect to the sound sources is of 90 dba at the corner of the Pendopo. Furthermore, the acoustic parameters of T sub is 1.2 to 2.2 s, clarity is +2 db, definition is 54% and IACC is 0.22 to 0.71, together makes Pendopo Mangkunegaran suitable to be used as a music hall. Further experiment should be conducted to find the value of the optimum acoustic parameters of Javanese Gamelan performance based on physio-and psycho-acoustic judgement, that can be used as parameters to design a concert hall for Javanese gamelan performance. ACKNOWLEDGEMENT We are must grateful to Pendopo Mangkunegaran Surakarta. BIBLIOGRAPHY SUYATNO, H. A. Tjokronegoro, Merthayasa IGN, R. Supanggah, Karakteristik Akustik Gamelan Jawa Studi Kasus Gamelan Milik PSTK ITB, SFA, ITS, 2013 ANDO Y., Architectural Acoustic, Springer, Japan, 1998 M. R. SCHROEDER, Springer handbook of Acoustic, Springer, USA, 2007 R. SUPANGGAH, Bothekan Karawitan, ISI Pers, 2002 Simone CAMPANINI, Angelo Farina, A new Audacity feature: room objective acoustical parameters calculation module, Departement of Industrial Engineering - University of Parma. RIBEIRO, Maria Rosa Sá, Room Acoustic Quality of a Multipurpose Hall: A Case Study, Centro de Estudos do Departamento de Engenharia Civil Faculdade de Engenharia da Universidade do Porto, 2003 J. SARWONO, Y. W. Lam, The preferred acoustic parameters for a Javanese Gamelan performance hall, Proceeding International Conference of Acoustics 17 th, Paris 2001 J. SARWONO, Y. W. Lam, The preferred ITDG and IACC for Javanese Gamelan performance hall, Jounal Sound and Vibration, 2002 SUYATNO, H. A. Tjokronegoro, IGN. Merthayasa, R. Supanggah, Pengaruh Tata Letak Instrumen Gamelan Jawa Di Panggung Terhadap Parameter Akustik Bagi Pengendang, Instrumentation Journal, KIM LIPPI, 2013