대학 내 사무실의 스피치 프라이버시 측정 및 평가

Measurement and evaluation of speech privacy in university office rooms

Abstract

본 논문에서는 대학 내 밀폐형 사무실의 SPC(Speech Privacy Class) 값을 측정하고 평가하였다. 대학 캠퍼스 내 3곳의 건물에 위치한 5곳 대상공간에서 실간 음압레벨차이(Level Difference, LD)와 수음실의 암소음 레벨($L_b$)을 각각 측정하였다. 5곳 대상공간은 모두 인접실과 복도가 인접해있다. SPC값을 도출하기 위해 필요한 LD값과 기존의 차음성능 측정방법인 투과손실(Transmission Loss, TL)을 함께 측정하여 비교하였다. 측정결과, 5곳 대상공간은 SPC 최소 기준치인 70을 만족하지 못하였다. 5곳 대상공간의 평균 $L_b$값은 29.2 dB이며 SPC 최소 기준치를 만족하기 위해서는 LD값이 41 dB 이상이어야 한다. SPC 최소 기준치를 만족하기 위해서 1/3옥타브밴드 160 Hz ~ 5000 Hz 주파수대역에서 평균 TL값은 40 dB 이상이 되도록 음향설계가 이루어져야 한다. LD값에 가장 큰 영향을 미치는 인자는 음원실과 수음실 간 인접벽체의 개구부 유무이다. 따라서 인접벽체에 개구부가 존재할 경우 차음성능이 높은 재료로 개구부를 대체하여 적절한 SPC값을 만족할 수 있다.

The speech privacy of closed office rooms located in a university campus was measured and assessed in terms of SPC (Speech Privacy Class) values. The measurements of two quantities, the LD (Level Difference) between a source and a receiving room, and the background noise level ($L_b$) at the receiving room were carried out in 5 rooms located in 3 different buildings in the university campus. Each of the 5 rooms was adjacent to both offices and corridors through walls. The TL (Transmission Loss) between the source and the receiver room was also measured to compare the difference of two standard methods, ASTM E2836-10 and KS F 2809. The present results show that the speech privacy of the 5 office rooms is not met the requirement for a minimum SPC values of 70. A minimum LD value of 41 dB between the source and the receiver room should be achieved for having a SPC value of 70 when the mean measured value of $L_b$ at the receiving room is 29.2 dB. That is, the TL(avg) value averaged over the octave bands from 160 Hz to 5000 Hz between the source and the receiver room should be or greater than 40 dB. The most important architectural factor influencing the LD value is the presence of openings, such as doors, and windows, on the adjacent walls between the source and receiving room. Therefore, if the opening of the adjacent wall is replaced by an opening with high sound insulation, the appropriate SPC value of the research and office rooms can be achieved.

Fig. 1. Measurement positions according to two standard methods (a) KS F 2809, and (b) ASTM E2638-10 in room #1.

Fig. 2. Measured 1/3 octave band T₃₀ values from 160 Hz to 5000 Hz and their mean values for two receiving rooms A, and B.

Fig. 3. Calculated 1/3 octave band total sound absorption values from 160 Hz to 5000 Hz and their mean values for two receiving rooms A, and B.

Fig. 4. Measured TL and LD values averaged from 160 Hz to 5000 Hz for 5 source rooms adjacent to each of receiving rooms (a) A and (b) B.

Fig. 5. Measured L₁₀, L₉₀, and L_avg values for 5 source rooms adjacent to each of receiving rooms (a) A and (b) B.

Fig. 6. Measured SPC values for 5 source rooms adjacent to each of receiving rooms (a) A and (b) B.

Table 1. Categories of speech privacy and their SPC values according to ASTM E2638-10.^[6]

Table 2. Data for 5 office rooms.

Table 3. Predictions and comparisons of TL and SPC values with or without openings on the adjacent walls by applying TL values in reference^[11] for a 45 mm thick wooden doors and a 6 mm thick single glass windows installed on a 200 mm thick concrete wall.