The letter H is represented by the International Phonetic Alphabet symbol /h/. It is a voiceless consonant and does not have voiced counterpart.
You will find the /h/ sound in words such as:
hair /her/
unhappy /ʌnˈhæpi/
rehearse /rɪˈhɜrs/
/h/ is a voiceless glottal sound. Glottal sounds are produced in the glottis, which are the two vocal folds above your windpipe. With this sound, you aren’t blocking or limiting airflow like you do with the other consonants. You will exhale air a little bit more than you would with vowel sounds to produce the /h/ sound.