As was demonstrated in this literature
review, the results of these studies vary but there
are many common findings across studies. For
compression speeds, it appears that audio can
be compressed up to 2.5 times (Ritzhaupt and
Barron, 2008) or 75% when presenting learners
with declarative information. However, when
presenting complex content (i.e., problem
solving or high level knowledge) instruction can only be presented at about 1.5 times or 25%
compression speeds (Pastore, 2009) and should
be in a multimedia environment, otherwise
learning will be inhibited and quickly diminish as
compression increases. For satisfaction, studies
show that learners do not prefer high speeds of
compression. Ritzhaupt, Gomes, and Barron
(2008) found that learners preferred speeds
around 1.4 times (20% compression speed) and
Pastore (in review) found that learners preferred
1.2 times (10%). As a result of these studies, a
series of design principles, discussed in the next
section of this paper, have been developed.