The solution for the decay of the steady state energy density in a diffuse field is given by, 4W acs e(t) e-C4vJ/m3 acs (a) Develop the general expression for the time t required for the sound pressure level to decay by X dB in terms of room surface area, volume, absorption coefficient and speed of sound. Consider that diffuse field intensity is defined in terms of e(t)C I= Pfms 4poc (b) An Industrial Warehouse with length 60 m, width 30 m and height 10 m is made from painted concrete floor and walls, with absorbent ceiling, where the front face of the Warehouse, is made entirely of glass. The absorption properties of the materials are given in Table 1 as a function of frequency. Calculate the average absorption coefficient in the warehouse as a function of frequency. Table 1: Room Acoustic Absorption Properties Frequency (Hz) 125 250 500 1000 2000 4000 0.1 0.25 0.7 0.85 0.7 0.6 a ceiling a painted concrete 0.01 0.05 0.06 0.07 0.09 0.08 a glass 0.35 0.25 0.18 0.12 0.07 0.04 (c) If the Warehouse in Part (b) commences with a steady state sound level of 100 dB at 1 kHz, predict the time it would take for the sound pressure level to decay to 50 dB at 1 kHz, if the noise source was switched off. The solution for the decay of the steady state energy density in a diffuse field is given by, 4W acs e(t) e-C4vJ/m3 acs (a) Develop the general expression for the time t required for the sound pressure level to decay by X dB in terms of room surface area, volume, absorption coefficient and speed of sound. Consider that diffuse field intensity is defined in terms of e(t)C I= Pfms 4poc (b) An Industrial Warehouse with length 60 m, width 30 m and height 10 m is made from painted concrete floor and walls, with absorbent ceiling, where the front face of the Warehouse, is made entirely of glass. The absorption properties of the materials are given in Table 1 as a function of frequency. Calculate the average absorption coefficient in the warehouse as a function of frequency. Table 1: Room Acoustic Absorption Properties Frequency (Hz) 125 250 500 1000 2000 4000 0.1 0.25 0.7 0.85 0.7 0.6 a ceiling a painted concrete 0.01 0.05 0.06 0.07 0.09 0.08 a glass 0.35 0.25 0.18 0.12 0.07 0.04 (c) If the Warehouse in Part (b) commences with a steady state sound level of 100 dB at 1 kHz, predict the time it would take for the sound pressure level to decay to 50 dB at 1 kHz, if the noise source was switched off