Korean in a Hurry. Samuel E. Martin

pat garden; pat‿to garden too CH’ T kkoch’ ‿ǔn flower (topic) kkot flower; kkot‿to flower too CH T nach‿e in the daytime nat daytime; nat‿to daytime too KK K pakk‿e outside pak outside; pak‿to outside too LK K talk‿i chicken (subj.) tak chicken; tak‿to chicken too

      There are certain other sound changes which are less regular. You may also notice sound variants. Sometimes the same thing will be pronounced in two different ways even by the same speaker. The most common of these is the dropping of h between voiced sounds:

man(h)i	lots	annyong(h)i	peacefully
pang(h)ak	school vacation	ǔn(h)aeng	bank
a(h)op	nine
You may also notice that w sometimes drops, especially after p, p’, pp, m, u, o:
chǒm(w)ǒn	clerk	sam(w)ǒl	March
kǔ(w)ǒl	September	o(w)ǒl	May
One irregular sound change which is quite common is the replacement of an initial p, t, ch, s, or k by their tense counterparts pp, tt, tch, ss, or kk. In this book, the “reinforcement” of the initial sound is sometimes shown with parentheses: (p)p, (t)t, (t)ch, (s)s, or (k)k. For example:
oje(p)pam	last night	yǒl-(t)tǔl	twelve

      NOTE 1: It is important to remember that b, d, j, g, and r are just positional variants of p, t, ch, k, and l respectively. B and p function as one sound unit in the structure of Korean and the native script (Han-gǔl) writes both with the same symbol. This is true also for d and t, j, and ch, g and k, r and l respectively. So when we speak of an ending beginning with t, it goes without saying we mean to add “(and this changes to d automatically between voiced sounds).”