Figure 1: Model of Mousa broch.
Figure 2: Model of Mousa broch broken down into sections.
Figure 3: Inside gallery showing narrow passage way.
Figure 4: Outline of courtyard.
Figure 5: Mousa broch 5 mic surround sound set-up. Forward-facing 3 microphones (stereo and centre): Windpac with stereo field (battery powered microphone) and shotgun (battery powered) microphone recorded by Fostex FR2. Rear-facing stereo: Neumans matched pair, powered and recorded by Sound Devices 744T.
Figure 6: Cell A reverb time 613 ms.
Figure 7: Cell B reverb time 914 ms.
Figure 8: Cell C reverb time 343 ms.
Figure 9: Gallery level 2 reverb time 329 ms.
Figure 10: Gallery level 3 reverberation time 395 ms.
Figure 11: Gallery level 4 reverberation time 264 ms.
Figure 12: Gallery 5 reverb time 209 ms.
Figure 13: Clack in entrance reverb time 327 ms.
Figure 14: Centre courtyard reverb time 332 ms. The open courtyard produces a characteristically low reverb time. The distance of the walls from the source sound clack and the lack of a roof show that direct sound is immediately dispersed and not reflected. This is a result to be expected from a clack sound recorded in the open air.
Figure 15: Halfway up stairs. Reverb time 594 ms.
Figure 16: Entrance. Iron bars analysis. 1 hit iron bars outside broch recorded in entrance. Frequencies between 1440 Hz - 2640 Hz peak and fade within 50 msecs.
Figure 17: Cell B. Iron bars analysis. Iron bars in courtyard recorded in cell B. The snapshot of the fft analysis shows the spike in amplitude at frequencies between 1440 Hz and 2640 Hz, the wave response shows that direct sound from the courtyard enters cell B and lasts for 150 msecs.
Figure 18: Cell A drum analysis (time vertical axis, frequency horizontal axis). 1 hit drum centre recorded in cell A, end time 120 msecs.
Figure 19: Cell C whistle analysis. Whistle centre recorded in cell C end time 1.520 msecs.
Figure 20: Entrance to the broch.
Figure 21: Courtyard with water tank.
Figure 22: Cross-sectional diagrams of cell A, from Paterson 1922.
Figure 23: Entrance to broch (on left) and entrance to cell A.
Figure 24: Cross-sectional diagrams of cell B, from Paterson 1922.
Figure 25: Entrance to cell B.
Figure 26: Cross-sectional diagrams of cell C, from Paterson 1922.
Figure 27: Entrance to stairs from courtyard.
Figure 28: View from the top of the broch at summer solstice 2009.
Figure 29: Entrance to broch and void set A.
Figure 30: Entrance to stairs and void set B.
Figure 31: Void set C above cell B.
Figure 32: Void set D.
Figure 33: Sun penetration entrance at 11.48 am. Broch entrance at bottom left of photo faces west.
Figure 34: At 11.50 am showing top of void set A and shadow of opposite wall head illuminated.
Figure 35: Sun penetration 12.00 pm. The sun continues its progress south and illuminates an area on the wall at the base of gallery 1, directly above cell A.
Figure 36: Sun penetration 12.50pm. The sun continues south and illuminates an area on the wall below the wall base, between cell A and small cell to left and below the stair entrance.
Figure 37: Solstice sun over stair entrance. 1.48 pm.
Figure 38: 1.38 pm. Illumination of cells next to stair.
Figure 39: 1.00 pm to 2.00 pm. Sunlight enters stair entrance illuminating the inside of the doorway.
Table 1: Details of void sets showing measurements of gallery chambers relative to ground/wall head and orientation of void sets.
Table 2: Showing dimensions used in model (estimated from Paterson’s 1922 survey).
Table 3: Showing dimensions of internal chambers for galleries 1–6 (based on Paterson’s 1922 survey).Table 4: Clack-generated reverberation times for spaces inside Mousa broch.
Table 5: Displacement time and frequency graphs for iron bars, drum and whistle sorted by location in broch with comments
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