Error Type 1: The schwa sound /ə/.

That is not only a problem for Indian learners but also for all learners regardless of their background.

For example, the word [available] has 3 schwa sounds, 2 of which are spelled as [a], which lead the learners to pronounce it as /a/.

This affects the rhythm and intonation of English. I usually recommend pronunciation teachers to teach the IPA (International Phonetic Alphabet) so that the learners can use it to identify the schwa sounds in a word.

It wouldn't take too long before the students realize that the schwa sound is quite common and worth paying extra attention to it.

wonderful; characterize; development; suggestion etc

Error Type 2: /ɔ:/

Indian learners seem to replace the long vowel /ɔ:/ with /ɑ/.

Instead of moving the lips to the front in a square shape, they keep the lips sort of idle and open the jaw slightly wider than it should be open which causes the tongue to go down too low.

The focus here should be on the lips moving forward in a square shape with the jaw sightly open.

Now, since vowel /ɔ:/ is often pronounced as /ɑ:/ in American English except when it's followed with an /r/, this is not considered to be a major error.

order; born; sword; court; dormitory; source etc

Error Type 3: /eɪ/

That is a fairly common problem among all learners of English especially Thai, Vietnamese, Chinese and of course Indians.

To pronounce vowel /eɪ/ correctly, the learners have to glide their tongue from one position to another. The tongue starts from a close-mid (jaw slightly open, tongue high) position with /e/ to close (jaw closed, tongue very high) with /j/.

Indian learners, like many others, find it difficult to perform the glide and alter the position of the tongue during pronouncing the vowel /eɪ/.

name; date; wait; train; great; same; wage etc

Error Type 4: /oʊ/

Like /eɪ/, this vowel is classified as a diphthong.  This means that the learners have to produce two sounds at the same time, a vowel /ɔ/ or /o/ and a consonant /w/. 

Indian speakers only pronounce vowel /ɔ/ and leave consonant /w/ out. 

Their lips stay idle and do not form a tight circle at the end of the sound as they should.

wrote; old; boat; coat; mode; road; showed etc.

Error Type 5: /w/

Mainly when it occurs before vowels /ʊ/, /i/ /ɪ/ or /e/, Indian learners confuse /w/ for /v/.

Again, consonant /w/ requires that both lips move forward to form a tight circle and when the lips stay idle and the lower lip somehow touches the upper teeth, the result is a sound that is similar to /v/.

would; with; women; ; wheel; womb; moving etc

Error Type 6: Voicing and de-voicing

Like Arabic speakers, Indian learners mispronounce /p/ at the beginning of words by voicing it (not consistently however) as a /b/.

Ironically, they mispronounce /b/ at the end of words by de-voicing it as a /p/.

Similarly, /t/ and /k/ may sound like /d/ and /g/ respectively at the beginning of words.

/p/ at the beginning: past; pardon; peel; poured etc/b/ at the end: rob; Forbe; curb; bulb; grab etc/t/ at the beginning: time; tall; toe; turtle etc/k/ at the beginning: character; Karma; carpet etc

Error Type 7: /θ/-/ð/

Both of these consonants require that the speakers place the tip of the tongue between the teeth and and let the air escape through a little gap between the tongue and teeth but Indian learners, like most learners of English, seem to find this quite difficult to manage.

What happens then is that they keep their tongue inside and press the tongue tip against their teeth resulting in /t/ instead of /θ/ and /d/ instead of /ð/.

think; both; father, that; mother; weather etc

Error Type 8: /s/ and /z/

That is not a very common problem for Indian learners who may confuse /z/ for either /ʒ/ or /ʤ/ and /s/ for /ʃ /.

It depends on what comes before or after /s/ and /z/.

Since the tongue tip in Hindi is often curled back when producing consonants, it comes into contact with the soft palate resulting in /ʃ / instead of /s/ and /ʒ/ instead of /z/.

The /s/ and /z/ in English require that the tip contact the alveolar ridge just behind the upper teeth, hence the confusion between the /s/ and /ʃ / or /z/ and /ʒ/ or /ʤ/.

/z/: hazard; zebra; zero; reservation; musical etc

/s/: sue; soon; suit; super etc

Error Type 9: /l/

As I explained above, due to the tongue tip's curl, the /l/ in Hindi is quite different from that in English.

In the case of the English /l/, the tongue body is low and only the tip is pressed against the alveolar ridge while air is freely flowing out through the gap between between the sides of the tongue and the upper teeth.

In the case of the Hindi /l/, the tongue body is higher, the tongue tip is pressing against the area between the soft palate and alveolar ridge, and so  the stream of air is more restricted as a larger area of the tongue is already in contact with the upper teeth.

Like; love; call; fallen; sold; deal; field etc

Error Type 10: /r/

In Hindi, the [r] has the same quality as the /t̬/ (the tap) in English. The tongue tip quickly taps the alveolar ridge.

The American /r/ does not allow any contact between the tongue tip and the roof of the mouth.

The root of the tongue moves back and rises until the sides of the tongue touch the gum above the upper teeth.

The tongue tip curls back and lips move forward at the same time. The British /r/ on the other hand is always silent at the end of the words and between a vowel and a consonant.

Indian learners often do pronounce the silent /r/.

road; cord; park; ordinary; letter; first etc

Error Type 11: /t/ and /d/

Due to the fact that the tongue tip is curled back in Hindi, it gives a different quality to voiced and voiceless consonants including /t/ and /d/.

Like many English consonants, /t/ and /d/ are produced by pressing the tongue tip against the alveolar ridge.

/t/: time; turtle; better; party; certify; short etc
/d/: dog; Madrid; code; ladder; drive; bedroom etc