In many situations where easy and continuous access to parts of a machine is necessary, a
complete enclosure may not be possible, and a partial enclosure must be considered (Alfredson
& Seow, 1976). However, the noise reductions that can be expected at specific locations from
partial enclosures are difficult to estimate and will depend upon the particular geometry. An
example of a partial enclosure is shown in Figure 10.22. Estimates of the sound power
reduction to be expected from various degrees of partial enclosure are presented in Figure 10.23.
Figure 10.23 shows fairly clearly that the enclosure walls should have a transmission loss of
about 20 dB, and the most sound power reduction that can be achieved is about 10 dB.
However, noise levels may in some cases be more greatly reduced, especially in areas
immediately behind solid parts of the enclosure.