wrong的w和hour的h为什么不发音?

wrong的w和hour的h为什么不发音?
如题：

辅字组的读音
辅字组
读 音
例 词
b
[b]
bike bus bag
[/]
bomb tomb
c
c在e前或在i/y前
[k]
cake picture coat music
[s]
face decide cinema
ch
[tF]
much chick rich teacher
[k]
school headache chemistry
[F]
machine
-ck
[k]
cock pocket black knock
d
[d]
doctor bread hand day
-dge
[dV]
bridge fridge
dr-
[dr]
children driver drink
f
[f]
five four breakfast
g
g在e i/y前
[^]
bag gardon go
[dV]
orange large German
gh
[f]
cough enough
[/]
light daughter high
gu- -gue
gu在非重读音节中
[^]
guess league dialogue
[^w]
language anguish
h
[h]
hot head house hand
[/]
hour honest
j
[dV]
jeep jar joke join July
k
[k]
kind bike skate make week
kn-
[n]
knife know knock
l
[l]
life milk school tall
m
[m]
monkey come autumn
-mn
[m]
autumn column
n
n在[k] [g]音前
[n]
not shine ten note
[N]
uncle thank hungry
-ng
[N]
morning young wrong
p
[p]
paper plane pig ship pen
ph
[f]
elephant photo telephone
q
[k]
Iraq
qu-
[kw]
quality quite
r
[r]
red rubber ruler
s在词首或清辅音前
元音字母间或浊辅音前
[s]
sit sleep desk
[z]
music husband
sc-
[sk]
scarlet
[s]
muscle science
sh
[F]
she fish shirt wash
t在通常情况下
在弱读字母ia ie io前
[t]
ten letter meet
[F]
patient nation
tch
[tF]
watch
th在通常情况下
在冠词 代词 介词 连词中
在词尾-the -ther中
[θ]
thin thirty method
[T]
the these with than
[T]
clothe father weather
tr-
[tr]
tree train country truck
v
[v]
very voice love leave
w
[w]
week win wake sweet wait
[/]
answer two 回答人的补充 2009-06-11 14:07 wh-
wh-在字母o前
[w]
what when white why
[h]
who whose whole
x
在重读元音前
[ks]
box text exercise
[gz]
examle exist exact
wr-
[r]
write
y-
[j]
yes yard yellow young
z
[z]
puzzle zero zoo
重读音节 单词中读音特别响亮的音节.用音标标记双音节,多音节词的读音时,应使用重读符号.单音节词多数是重读音节,标记读音时不需要使用重读符号.
开音节 ①绝对开音节:单个元音字母后面没有辅字组的重读音节.例如:no blue ba-by stu-dent se-cret.
②相对开音节:单个元音字母后面加单个辅音字母,再加一个不发音字母e构成的重读音节.例如:name these bike home ex-cuse.
闭音节 单个元音字母后面有辅字组(r w y 除外)且以辅字组结尾的重读音节.例如:bag egg fish not cup
多音节词重读规则 多音节词通常在倒数第三个音节重读.
例如:el-e-phant con-grat-u- la-tion
词尾有-ic或-tion,-sion的词,在-ic或-sion,-tion前的一个音节上重读.例如:scien tific im pression nation