1)Diphthongization after palatal consonants(palatalization)

Diphthongs may have resulted from another process in Old English - diphthongization after palatal consonants sk’, k’ and j (in spelling c, sc, ʒ ):

a > ea skal - sceal (shall), scamu - sceamu (shame)

ā > ēa skaggwon - scēawian (to show)

e > ie ʒefan - ʒiefan (give) ʒetan - ʒietan (get)

æ > ea (the æ sound was actually derived from a) ʒæst - ʒeat (gate)

ǣ > ēa (the ǣ sound was actually derived from ā ) jar - ʒēar (year)

o > eo scort - sceort (short) yong - ʒeonʒ (young)

However, there are linguists who still doubt whether the i sound (that is the resulting sound, it was actually a diphthong) was pronounced. Some stick to the opinion that the letter i simply signified the palatal nature of the preceding sound.

The words beginning with ʒ, sc and c with non-palatalized vowel represent dialects other that West-Saxon (ʒunʒ, ʒefan) etc.

2)Contraction

Somehow or other the consonant h proved to have interfered with the development of many sounds. When h was placed between two vowels the following changes occurred:

a + h +vowel > ēa slahan - slēan (slay)

e + h + vowel > ēo sehen - sēon (see)

i + h + vowel > ēo tihan - tēon (accuse)

o + h + vowel > ō fohan - fōn (catch)

3)The significant quantitative change that is still felt in present-day English is the lengthening of vowels before the clusters nd,ld, mb - bindan, cild, climban (bind, child, climb). Further development of the sound system led to diphthongization of long vowels, and that explains the exception in the rules of reading the sounds in the closed syllables in the present-day English (the words like climb, find, bold, told, comb, bomb).Still, if there was a consonant after this cluster the vowel was not lengthened: cildru (now children).

9.Old English Consonants. Phonetic Changes

Voiceless fricatives appeared in Germanic languages as a result of the First Consonant Shift (Grimm’s Law). Proceeding from a changeable part of the consonant system (it is to be remembered that the stablest are the sonorants and the sibilant s) their development continues in Old English.

1) Voicing of fricatives in intervocal position

f > v ofer (over)hlāf - hlāfas (loaf - loaves)

θ > ð ōðer (other) ; raðe (quickly)

s > z > r

Voiced sibilant z was very unstable in Old English, and very soon changed into r. This process is called rhotacism.

wesun - weren ( now were, but was) maiza - māra ( now more, but most)

It is due to rhotacism that common Indo-European suffix -iza (Ukr.- iш) used to form the degrees of comparison is so different now in Ukrainian and English, but comparing such words as Goth, softiza Ukr. тихіший Old English softra ME softer we may easily find that the suffix is essentially the same.2) Palatalization of the sounds k”, sk’ and kg ’ (marked as c, sc and cʒ) developed in assibilation, that is formation of a sibilant in places before front vowels.

k’>tʃ cild (child) ceosan (choose) hwilc (which)

sk’ > ʃ sceal (shall) sceotan (shoot) sceort (short)

kg’ > dʒ brycʒ (bridge) hrycʒ (ridge) wecʒ (wedge)

Back ɣ sound before palatal consonants turned into j - ʒear (year).

So, the words that started with sc or j acquired a sibilant or j; if we find that a word still has g or sc/sk at the beginning there is a strong probability that it was borrowed from Scandinavian and replaced the Old English form (e.g. give, skin) or together with the old word formed a pair of etymological doublets (shatter/scatter, shirt/skirt). Some words of Greek origin (school, scheme etc) will also have sk.

3) Assimilation before t. The sound t when it was preceded by a number of consonants changed the quality of a preceding sound.

velar +t > ht secan - (sōcte) —> sōhte (seek - sought) wyrcan —> worhte (work - wrought) (the sounds k and g changed in the past tense and in the participle II before the dental suffix)

labial + t > ft ʒesceapan —> ʒeaseaft (creature)

dental + t > ss witan —> wisse (instead of witte - knew) 

fn>mn stefn —> stemn (voice); fm>mm wifman —> wimman (woman)

dð>t bindð —> bint (binds)

4) Loss of consonants in certain positions. Besides h that was lost in intervocal position, the sounds n and m were lost before h, entailing the lengthening of the preceding vowel: fimf - fif (five) onðer - ōðer (other)

Other examples of similar loss was the loss of ʒ before d and n; the vowel was lengthened, too: mæʒden - mǣden (maiden) sæʒde - sǣde (said)

5) Metathesis of r. In several Old English words the following change of the position of consonants takes place:

cons+ r + vowel > cons + vowel + r

brunnan - burnan (burn); brenna - beorn (a warrior); hros - hors (horse)

Metathesis of sounds is observed also with other sounds: wascan - waxan (wash)

6.West Germanic gemination of consonants. In the process of palatal mutation, when j was lost and the preceding vowel was short, the consonant after it was doubled (geminated): fullian - fyllan (fill); talian - tellan (tell) 

As we can see, the changes in Old English sounds were for the most part reflected in spelling, and we must only rely on the corresponding words from other languages to see what the origin of this or that sound was. The exceptions are only in such instances as various developments of ʒ, voicing of fricatives and palatalization of c, sc, cʒ.