Speech understanding
A person’s hearing threshold is the level
of loudness above which a person can hear sounds. Sounds that are softer (quieter) cannot be heard.
People
with normal hearing can hear quieter sounds than people with a hearing loss. Speech consists of combinations
of vowels and consonants. Normally, vowels are perceived as louder than some of the consonants.
Normal
hearing
People with normal hearing can hear all the sounds that are a part of speech
(and other environmental sounds) at normal levels of loudness. When each speech sound is perceived at
its normal loudness, words are easily recognised, and it is possible to carry on a conversation even
in the presence of background noise.
Normal
hearing threshold: All speech sounds and environmental sounds are at a level of loudness above the hearing
threshold and can therefore be heard.
Hearing loss
When
a person suffers a hearing loss, it becomes difficult for that person to hear consonants of either soft
or medium loudness. It can therefore be difficult for the person to distinguish between words that are
closely related phonetically, such as “star” and "tar."
When
background noise is present, it becomes even more difficult to recognise speech sounds and understand
what is being said. And because background noise often has a lower pitch and is louder than speech,
speech is masked, even though speech is the sound the listener is most interested in hearing.
Typical age-related abnormal hearing threshold: Some speech sounds (and environmental sounds) are at a level of loudness below the hearing threshold and are therefore no longer audible (grey area).
