Your hearing profile graphically depicts which sounds fall within your natural hearing range, and which sounds fall outside of it.
As we shall see, this is particularly relevant to our ability to understand speech.
Example 1: 100% Speech Availability
Speech is like a jigsaw puzzle: we ideally want ALL the pieces available to us so we can make out what others are saying first time, accurately. We can see this on the illustration.
The quietest sound this person can hear is 10 dB (decibels) across all pitches. It’s shown on the illustration as the red circles and line.
Any sounds that fall above this red line (e.g. 0 dB) would be OUTSIDE of this person’s HEARING RANGE. But in this person’s case, all the sounds that make up speech (shown as the yellow banana-like area) are well below their red line. It means they have ALL the pieces of speech’s jigsaw puzzle available to them.
Example 2: 70% Speech Availability
The next illustration is different. Here some of their red line crosses into the speech area, meaning that specific sounds (such as the ‘s’, ‘f’, ‘th’ and ‘t’) now fall outside of this person’s hearing range. This effectively removes these speech sounds from any conversation they’re listening to or any dialogue on TV.
You can get some idea of how speech becomes degraded by trying to read the speech bubble on the right of the diagram. Imagine that the keyboard on your computer was missing keys for ‘s’, ‘t’, ‘f’ and (let’s pretend) ‘th’. Notice how some words remain perfectly legible (like “rainbow”), whilst other words like “rike” no longer make sense, and other words like “pa” become ambiguous.
You can still follow the gist of the passage, but you have to guess more or wait until you can pick up more context. Simply put, it takes more effort and slows your understanding down.
The more speech sounds that fall outside of a person’s hearing range, the greater the ambiguity and incomprehension. The greater the ambiguity and incomprehension, the more effort it takes and the slow our processing. We see this in the next example.
Example 3: 15% Speech Availability
The next illustration shows what happens when most (but not quite all) of the sounds within speech fall outside of someone’s hearing range. In the speech bubble on the right, you’ll notice that very few words are left intact.
Even though this person can hear most of the vowels (and some consonants, like the ‘m’ and ‘n’), it’s not sufficient to make sense of everyday speech. That’s because it’s the consonants that give an individual word its meaning.
Imagine if everyone just spoke to us in vowels, with no consonants. All the beginnings and endings of words would disappear and everyone would sound like infants learning to speak. They’d use the same ‘words’ for lots of different things. For example: ‘-a-’ could be ‘cat’ of ‘sat’ or ‘pat’ or ‘hat’. It could even be ‘tap’ or ‘sack’. So the amount of ambiguity in speech rises exponentially.
Conversation now becomes so much effort, it’s hardly worth bothering with. Much easier not to get involved in the first place, maybe?
Example 5: Audified hearing
In our final example, we’ve taken one of the hearing profiles illustrated above and remapped the speech sounds so they are now falling back within the hearing range.
This is made possible with modern hearing technology. Once we’ve profiled your hearing, we can then use digital sound processing to specifically identify which sounds are falling outside your natural hearing.
Rather than simply turning everything up (which would just make everything too loud), we want to remap those sounds so they fit more precisely and naturally within your own hearing range. That’s why we talk about ‘audifying’ rather than ‘amplifying’: it’s tailored to your hearing profile.
Example 3: 15% Speech Availability
The next illustration shows what happens when most (but not quite all) of the sounds within speech fall outside of someone’s hearing range. In the speech bubble on the right, you’ll notice that very few words are left intact.
Even though this person can hear most of the vowels (and some consonants, like the ‘m’ and ‘n’), it’s not sufficient to make sense of everyday speech. That’s because it’s the consonants that give an individual word its meaning.
Imagine if everyone just spoke to us in vowels, with no consonants. All the beginnings and endings of words would disappear and everyone would sound like infants learning to speak. They’d use the same ‘words’ for lots of different things. For example: ‘-a-’ could be ‘cat’ of ‘sat’ or ‘pat’ or ‘hat’. It could even be ‘tap’ or ‘sack’. So the amount of ambiguity in speech rises exponentially.
Conversation now becomes so much effort, it’s hardly worth bothering with. Much easier not to get involved in the first place, maybe?
