http://www.greatscott.com/hiero/hiero_alpha.html
Alphabet characters were the basis for hieroglyphic writings. The basic hieroglyph characters are refered to as the ALPHABET. They 'spell out' names or anything which can't be represented by other characters. The alphabet characters are read as the sound of the object they represented.
Although vowels were used in the spoken language, they were not usually written unless a word begins with a vowel or where it might be confusing if left out…like with names.

EXAMPLE
In english, words are often abbreviated by leaving out vowels.
mtn = mountain
blvd = boulevard
When these abbreviations are read aloud, they are spoken using vowels.
The Hieroglyphic Alphabet
HIEROGLYPH REPRESENTS PRONOUNCED
HIEROGLYPH
REPRESENTS
PRONOUNCED
vulture
ah
(father)
reed
i(filled)
two
reeds
y (discovery)
arm &
hand
broad a
(car)
quail
chick
oo(too)or
w (wet)
foot
b
(boot)
mat
p(pedestal)
horned
viper
f(feel)
owl
m
(moon)
water
n(noon)
mouth
r
(right)
reed shelter
h
(hat)
twisted flax
h!
(ha!)
placenta
kh
(like Scotch 'loch')
animal's belly
ch
(like German 'ich')
folded cloth
s
(saw)
door bolt
s
(saw)
pool
sh
(show)
slope of hill
k
(key)
basket
with handle
k
(basket)
jar stand
g
(go)
loaf
t
(tap)
tethering rope
tj
(church)
hand
d
(dog)
snake
dj
(adjust)
You may notice that some hieroglyphs are vowel sounds, these are considered weak consonants and are used when a word begins with a vowel or where it might be confusing without them, like in a name.