공연장의 음향개선을 위한 음향 확산체 설계 연구

Abstract

외 챔버 뮤직홀의 용적 및 잔향시간의 조사를 통하여 예상되었던 1.4∼1.5초를 만족하는 것으로 나타났다. 중규모 공연장의 확산설계 사례로서 리모델링되는 공연장은 확산체의 형상을 세 가지 형태의 사각형 모듈을 적용하였으며, 각 모듈을 125 Hz의 반파장에 해당하는 1.4 m 길이의 정사각형 평면에 배치하였다. 모든 확산체는 밀도가 높은 GRG로 제작되었으며 단면형태는 수직 및 수평방향 모두 중앙부에서 최대, 경계부분에서 최소 높이를, 각 박스형 모듈은 5 cm 간격으로 5-25cm 높이를 갖도록 설계하여 초기 음을 다양한 방향으로 난반사하게 하며, 특히 확산체의 중앙부 아래 면에서 반사되는 초기반사음은 아래쪽 객석방향으로 전달되어 객석에서 풍부한 확산음장이 조성되도록 하였다. 또한 고주파 대역에서의 추가적인 확산효과를 위해 각 모듈의 표면에는 요철을 추가하였다. 확산계수는 (500Hz부터 3.15 kHz까지의 1/3옥타브밴드 대역 평균) 약 0.75로써 이전 연구에서 높은 확산률을 갖는 것으로 나타난 직경 40 mm의 반구형 확산체와 유사한 것으로 나타났다. 1 kHz 이상의 고주파수 대역부터 확산계수가 크게 증가하는 것으로 나타나 연극이나 뮤지컬과 같은 높은 음성명료도를 요구하는 공연장에서 적합할 것으로 판단된다. 확산체의 적용에 따른 음향성능 예측을 위해 1:25 축소모형을 제작하여 성능예측을 하였으며 음향개선 후 확산음장조성 여부를 확인하기 위해 측정한 결과 평균 6.27의 높은 TD값과 공간감 지표인 1-IACCE3은 0.60 이상의 높은 분포와 1 kHz 이상 대역에서 0.5 이상의 높은 확산계수를 갖는 것으로 나타나 측벽 확산체를 통한 공간감 개선의 효과가 입증되었다. 대규모 공연장의 확산설계 사례로서 리모델링 되는 공연장은 초기반사음을 전 객석에 고루 전달하여 공간감과 음압을 개선하기 위한 반사구조를 설계하였다. 주요 반사구조로는 오케스트라 쉘, 천장반사판, 천장 돌출구조, 후벽 돌출구조, 측벽반사판, 테라스 형 객석 설치 및 측면 발코니 석을 고려하였다. 각 반사 구조 체의 형상과 설치 위치는 해당 부재만 제작하는 방식으로 1:10 scale model을 반무향실에 설치하여 음향성능을 측정하고, 컴퓨터 시뮬레이션을 통한 층별 공간감 및 음압분포에 대한 분석결과에 따라 결정하였다. 무대 용적이 작을수록 객석에서의 음압레벨이 증가하기 때문에 오케스트라 쉘은 공연에 필요한 최소 바닥면적을 기준으로 최소한의 용적을 갖도록 하였으며, 평면 벌어짐 각도와 단면 형상은 반사음선 분포를 기준으로 1층부터 3층 객석 전체에 1차 반사음을 전달할 수 있도록 Genetic Algorithm을 통해 최적화 하였다. 오케스트라 쉘은 다른 반사구조와 동일하게 저주파의 음향반사를 고려하여 4-9m2의 삼각형 모듈로 구성하였으며, 공연의 규모에 따라 무대 크기 및 용적을 조절할 수 있도록 가변무대가 계획되었다. 천장반사판은 주파수 대역별로 평탄한 전달함수를 나타내는 6m2 크기의 삼각 모듈로 형상과 개구율 변화에 따른 영향을 검토 후 최적 형상을 도출하여 구성되었으며, 한 열 당 4∼5개의 모듈로 계획하여 무대쪽 2열이 2층 객석을, 그리고 이후 2열이 3층 객석에 반사음을 전달할 수 있도록 각도를 조정하여 설치하였다. 무대와 멀리 떨어진 3층 객석 후열의 공간감 및 음압레벨 증가를 위한 후벽 돌출구조는 반사음선 작도를 통해 기본 형상을 계획한 후 Genetic Algorithm을 활용하여 각 면의 설치각도와 길이를 최적화 하였다. 또한 측면 발코니 석을 설치하여 중앙부 객석에 측벽간 거리가 18m인 대향벽체를 조성하여 공간감 요소가 취약한 1층 중앙부 객석에 측면 발코니석 벽체로부터의 반사음이 전달되도록 하였다. 이러한 확산음장 조성을 위해 제안된 개선설계안들의 음향성능을 컴퓨터 시뮬레이션, 1:10 오픈 형 축소모형, 1:50과 1:100 축소모형 등을 통해 평가하였다. 시뮬레이션 평가결과, 실내 마감재료 변경을 통해 잔향시간이 크게 증가하는 것으로 나타났으며, 객석구조의 추가 설계는 객석 중앙부에서의 공간감 및 전체적인 음압레벨 개선에 기여하는 것으로 나타났다. 또한 오케스트라 쉘 및 각 반사판들은 목표한 각 객석에서의 공간감 및 음압레벨 개선에 효과가 있는 것으로 나타났다. 그리고 각 장르별 음향측정 결과 콘서트모드에서 잔향시간 2.2초, 초기감쇠시간 2.6초, 음의 세기 4.2dB, 명료도 0.1dB, LF 0.21 등 모든 음향지표가 설계 목표치를 만족하는 것으로 예측되었으며, 콘서트모드에 잔향가변장치들을 적용하여 측정한 결과 오페라모드, 뮤지컬과 드라마 모드 등에서도 각 장르에 적합한 음향지표들의 개선효과를 보여 확산체를 사용한 확산음장조성이 무대와 객석음향 개선의 방안으로서 제시될 수 있다.|In this paper, acoustical renovation design process using scattering sound field of the Small, Medium and Grand theatres for modifying purpose from conference to recital, securing the acoustical multi-purposes and the acoustical quality were investigated. The area of the existing Small-theatre was about 612 m2 and it has been used mainly for meeting, symposium and other functional events. The leaf-shaped floor plan and tilted side balconies (a slope of 1:10) within 16 m width between side walls were designed to increase lateral reflection. To provide maximized intimacy, the continental style and every-other-row seating arrangement without center isle was planned. The saw-tooth shaped GRC (Glass-fiber Reinforced Concrete) wall reflectors and the protruded rear wall of the stage were designed for spatial responsiveness of the hall. Also, in this paper the material characteristics of diffusers for acoustical renovation of existing small performing spaces were shown high density and diverse radius sound diffuser. Consideration is given to acoustical effects on sound fields through the practical case of small performing hall. After acoustical renovation using the sound diffusers, the Small theatre has 456-seats with a volume of 3,212m3. Its unoccupied RT is 1.44 s and the average of 1-IACC (Interaural Cross-correlation Coefficient) is 0.71. The Medium-theater was a proscenium theater with 447 seats, which was built in 1978. Acoustical remodeling design of the theater was carried out to improve the acoustic quality in audience area and to meet functional requirements of the theater. Design strategies included use of more reflective surfaces, installation of diffusers on sidewalls and orchestra pit, and side balconies. In particular, sidewall diffusers were designed through measurements of scattering coefficients according to ISO standard. The Medium-theater was renovated as a live and intimate space for the dramatic and musical performances with a design that included more seats on the upper floors and additional spaces above ceiling reflectors. The vertically-patterned diffuser profile with protruded cubic surfaces in the Midium-theater was designed using glass-fiber reinforced gypsum for sound diffusion in the major speech frequency range. Designed diffuser profiles were evaluated for the hall by measurements of scattering and diffusion coefficients of the 1:10 scale model diffusers. The effects of diffusers in the hall were also investigated by covering lateral walls close to the stages with reflective materials to control diffusive surfaces. As a result, spatial uniformity increased with diffusive wall profiles in this hall. After acoustical renovation, field measurements were performed to validate the acoustical design. The results was shown that unoccupied reverberation time varied from 0.93 to 1.06 s, and 1-IACC (Interaural Cross-correlation Coefficient) was more than 0.60. It was also found that sidewall diffusers resulted in decreases of COV (coefficient of variation) of early decay time and 1-IACC and increases of and Np (number of peak). Furthermore, the balance, refers to the sound power ratio of the stage and the pit sources, was -0.2 dB. Averaged Temporal diffusion (TD) from the auto-correlation function (ACF) of impulse responses was 6.05 to 6.30 by measurement cases. RT was found to be the most related factor to diffusion power (R=0.94). The correlation between TD and EDT was high (R=0.73). In addition, the effects of diffuser-installed location were discussed in terms of acoustical parameter variation. The Grand-theater is a proscenium theater with 3,022 seats. Originally built in 1978, the first renovation was conducted in 2004 to provide variable RT using a ‘sound system’. Recently, a renovation was again planned to enhance the acoustic quality, especially sound strength (G) and spatial responsiveness, based on architectural acoustics design. The orchestra shell and various ceiling and wall reflectors were designed to improve the G and IACC. The side balconies were added to provide lateral reflections to the audience at the stalls area. Materials of the walls and chairs were changed for longer RT and higher G. The results of a computer simulation as well as the acoustical design process are presented. The effects of various reflecting surfaces on the audience G and IACC were investigated by using open-type 1:10 scale model. The orchestra shell and 3 types of reflector were designed to increase the G and 1-IACCE3. The reflectors were composed of triangular panels and the area of basic module was designed as 9 m2, based on the previous study [Nakagima et al. J.Acoust.Soc.Am.92,1443– 본 연구는 확산체 설계를 통한 확산음장 조성으로 기존 공연장의 음환경을 개선하기 위해 객석과 무대의 확산 profile, 부착위치, 재료의 성상, 반사면이 음장조성에 미치는 영향에 관하여 연구하였다. 또한 확산계수 측정결과를 바탕으로 반사면과 확산체의 형상, 재료, 설치위치에 따른 영향을 각 음향지표의 변화양상을 통해 논의되었다. 제 1 장은 연구배경과 목적, 이전연구 및 연구방법 등을 기술하였으며 제 2장에서는 확산체 설계, 음향예측 방법과 확산율 평가지표, 제3장은 소규모 공연장의 평면 형태 변경과 경사벽면 설치 그리고 다양한 곡률의 톱니바퀴 모양의 확산체 설치와 무대 돌출 후벽 등을 통한 음향개선을 연구하였으며 제4장은 중규모 공연장에서의 사각 모듈 형태의 중앙부에서 최대, 가장자리에서 낮은 높이를 가진 벽면 확산체와, 천장반사판을 설치하여 음향개선 연구사례를 제 5 장은 대규모 공연장의 오케스트라 쉘을 공연규모에 따라 가변할 수 있도록 개선하고, 천장반사판, 천장 돌출구조와 후벽 돌출구조, 측벽반사판, 테라스형 객석 등의 반사면 설치와 측벽 확산체 설치를 통한 음향개선 연구를 하였다. 그리고 제 6 장은 결론을 기술하였다. 소규모 공연장의 사례에서는 벽과 천장의 반사와 확산성능 확보를 위하여 홀의 평면을 기존의 정사각형 형태에서, 나뭇잎형상인 직사각형 형태와 역 부채꼴(Reverse Fan) 형태를 동시에 적용하는 변형된 평면을 계획하였다. 직사각형형태를 통해 객석부에 강한 측면 반사음과 높은 공간감을 제공하도록 하였으며 객석후부로 갈수록 측벽간의 거리가 짧아지는 역부채꼴 형태를 적용하여 객석후부에 초기반사음을 보강하여 명료성을 증대시킬 수 있도록 하였다. 객석에서의 강한 측면 반사음 제공을 위해 기울기가 1:10인 경사 벽면을 설치하여 측면반사음비율의 표준편차 최소와 고른 측면반사음 분포를 확보하였다. 확산체는 특정 주파수 대역에서만의 확산을 방지하기 위하여 다양한 곡률 반지름 (R = 1350㎜, 737㎜, 4109㎜ 등)을 가진 톱니 형태로 설계하여 전 주파수대역에서 확산을 유도하였다. 음향개선 후 측정 결과, 공간감을 나타내는 객관적 지표인 BQI (Binaural Quality Index,1-IACC)지수가 평균 0.72의 값을 유지하며, 무대는 -7.2 dB에서 -8.3 dB의 ST1 분포를 나타내어 무대에서 연주자들이 서로의 연주를 듣거나 자신의 연주를 모니터링 하는데 우수한 음향성능을 지닌 것으로 확인되었다. 잔향시간 (RT)은 1.44초로 음향설계 지표의 설정 시 국내∙ 1451(1992)]. .In addition, the shape of reflectors was optimized by genetic algorithm to increase G and 1-IACC. In the end, open-type 1:10 scale model measurements were conducted to investigate the effect of reflectors on early sound in the auditorium. The results indicated that sound energy (G or SPL) and IACC were changed around 0.29 and 5.7 dB, respectively, when reflectors were installed. In addition, the acoustical qualities of the remodeled hall were evaluated using computer simulations and 1:50 scale model measurement. The results show that G was improved by 5 dB and BQI by 0.24, whereas the occupied RT at mid-frequencies became variable from 1.47 to 2.24 sec.; In this paper, acoustical renovation design process using scattering sound field of the Small, Medium and Grand theatres for modifying purpose from conference to recital, securing the acoustical multi-purposes and the acoustical quality were investigated. The area of the existing Small-theatre was about 612 m2 and it has been used mainly for meeting, symposium and other functional events. The leaf-shaped floor plan and tilted side balconies (a slope of 1:10) within 16 m width between side walls were designed to increase lateral reflection. To provide maximized intimacy, the continental style and every-other-row seating arrangement without center isle was planned. The saw-tooth shaped GRC (Glass-fiber Reinforced Concrete) wall reflectors and the protruded rear wall of the stage were designed for spatial responsiveness of the hall. Also, in this paper the material characteristics of diffusers for acoustical renovation of existing small performing spaces were shown high density and diverse radius sound diffuser. Consideration is given to acoustical effects on sound fields through the practical case of small performing hall. After acoustical renovation using the sound diffusers, the Small theatre has 456-seats with a volume of 3,212m3. Its unoccupied RT is 1.44 s and the average of 1-IACC (Interaural Cross-correlation Coefficient) is 0.71. The Medium-theater was a proscenium theater with 447 seats, which was built in 1978. Acoustical remodeling design of the theater was carried out to improve the acoustic quality in audience area and to meet functional requirements of the theater. Design strategies included use of more reflective surfaces, installation of diffusers on sidewalls and orchestra pit, and side balconies. In particular, sidewall diffusers were designed through measurements of scattering coefficients according to ISO standard. The Medium-theater was renovated as a live and intimate space for the dramatic and musical performances with a design that included more seats on the upper floors and additional spaces above ceiling reflectors. The vertically-patterned diffuser profile with protruded cubic surfaces in the Midium-theater was designed using glass-fiber reinforced gypsum for sound diffusion in the major speech frequency range. Designed diffuser profiles were evaluated for the hall by measurements of scattering and diffusion coefficients of the 1:10 scale model diffusers. The effects of diffusers in the hall were also investigated by covering lateral walls close to the stages with reflective materials to control diffusive surfaces. As a result, spatial uniformity increased with diffusive wall profiles in this hall. After acoustical renovation, field measurements were performed to validate the acoustical design. The results was shown that unoccupied reverberation time varied from 0.93 to 1.06 s, and 1-IACC (Interaural Cross-correlation Coefficient) was more than 0.60. It was also found that sidewall diffusers resulted in decreases of COV (coefficient of variation) of early decay time and 1-IACC and increases of and Np (number of peak). Furthermore, the balance, refers to the sound power ratio of the stage and the pit sources, was -0.2 dB. Averaged Temporal diffusion (TD) from the auto-correlation function (ACF) of impulse responses was 6.05 to 6.30 by measurement cases. RT was found to be the most related factor to diffusion power (R=0.94). The correlation between TD and EDT was high (R=0.73). In addition, the effects of diffuser-installed location were discussed in terms of acoustical parameter variation. The Grand-theater is a proscenium theater with 3,022 seats. Originally built in 1978, the first renovation was conducted in 2004 to provide variable RT using a ‘sound system’. Recently, a renovation was again planned to enhance the acoustic quality, especially sound strength (G) and spatial responsiveness, based on architectural acoustics design. The orchestra shell and various ceiling and wall reflectors were designed to improve the G and IACC. The side balconies were added to provide lateral reflections to the audience at the stalls area. Materials of the walls and chairs were changed for longer RT and higher G. The results of a computer simulation as well as the acoustical design process are presented. The effects of various reflecting surfaces on the audience G and IACC were investigated by using open-type 1:10 scale model. The orchestra shell and 3 types of reflector were designed to increase the G and 1-IACCE3. The reflectors were composed of triangular panels and the area of basic module was designed as 9 m2, based on the previous study [Nakagima et al. J.Acoust.Soc.Am.92,1443&#8211