What is Voiceless?
Voiceless consonants do not use the voice. They are percussive and use hard sounds. Once again, you can test if a consonant is voiceless by putting your finger on your throat. You will feel no vibration in your throat, just a short explosion of air as you pronounce. Pronounce each of these consonant sounds and feel NO vibration in your throat.
ptksshchth (as in thing)
Careful! Some Consonants Voiced, but are Voiceless
When consonants are put in groups they can change the voiced or voiceless quality of the consonant that follows. A great example of this is the past simple form of regular verbs. As you know, regular verbs add -ed to the end of the verb in the past simple.
play - playedwash - washedlive - lived etc.
These past simple verbs all end in '-ed'. However, some of the verbs are pronounced with a voiceless 't' sound and some are pronounced with the voiced 'd' sound. Why? Here are the rules:
If -ed is preceded by a voiceless consonant sound (p, k, sh, etc.) -ed sounds as a voiceless 't'. Remember that the 'e' is silent.
If -ed is preceded by a voiced consonant sound (d, b, v, etc.) -ed sounds as a voiced 'd'. Remember that the 'e' is silent.
If -ed is preceded by a vowel sound (often 'ay') -ed sounds as a voiced 'd' because vowels are always voiced. Remember that the 'e' is silent.
Exception: If -ed is preceded by 't' pronounce a voiced -id. In this case, the 'e' is pronounced.
This pattern can also be found with plural forms. If the consonant preceding the 's' is voiced, 's' will sound as voiced 'z':
chairsmachinesbags
If the consonant preceding the 's' is voiceless, 's' will sound as voiceless 's':
batsparkspipes
Connected Speech
Finally, when speaking in sentences the ending consonant sounds can change based on the following words. This is often referred to as 'connected speech'. Here is an example of a change from a voiced 'b' in the word 'club' to a voiceless 'p' because of the voiced 't' of 'to' of the following word:
We went to the club to meet some friends.
Here is an example of a change from a voiced 'd' past simple verb changed to voiceless 't':
We played tennis yesterday afternoon.