Consonants are high frequency sounds that are critical to understanding speech.
Think about it, would you prefer to spend the rest of your life speaking only consonants or vowels? Here is a sentence with vowels only...
Here is a similar sentence in consonants only...
"Wth cnsnts y cn lmst ndrstnd vr thng!"
You will see the impact of this later when we discuss hearing and types of hearing loss.
We will discuss a sensory neural (nerve) loss that often effects more radically the higher frequencies. Hence, babies can be born with a high frequency loss that would preclude their hearing consonants but not speech.
These children would appear anything but deaf since they would respond to sounds, even soft ones (because of their low frequency components); but would not develop language or speech because they couldn't hear the consonants.