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 recognized, 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 recognize 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).