Threshold Levels and Suprathreshold levels: In the term of hearing, Threshold is the weakest stimulus that an organism can detect and Suprathreshold refers to speech presented above the Threshold of the listener.
The term threshold in general means the point or level at which something happens to occur. In the context of audiology hearing threshold means the sound level below which a person cannot hear but from that particular sound level the person begins to hear.
Absolute threshold: The lowest level at which a stimulus can be detected.
Recognition threshold: The level at which a stimulus can not only be detected but also recognized.
Differential threshold: The level at which an increase in a detected stimulus can be perceived.
Absolute threshold of hearing (ATH)
Absolute threshold of hearing (ATH) is the minimum sound level of a pure tone that an average human ear with normal hearing can hear with no other sound present. The absolute threshold relates to the sound that can just be heard by the organism. The absolute threshold is not a discrete point, and is therefore classed as the point at which a sound elicits a response a specified percentage of the time.This is also known as the auditory threshold. The auditory threshold needs an relative sound level. Therefore in case of normal hearing ATH is usually considered 0 dB. As a result of which threshold estimation becomes easy to calculate.
Suprathreshold refers to speech presented above the auditory threshold of the listener.
The prefix ” Supra” from the basic word supra threshold means “above” or “beyond”. When extra stimulus is provided beyond the threshold , it is called Supra threshold. It mainly facilities the speech processing in the brain(decode)/speech recognition.
Measurement of suprathreshold speech recognition allows clinicians to assess a patient’s speech communication ability in a controlled and systematic manner. The results can help clinicians distinguish between different causes of hearing loss and plan and evaluate audiological rehabilitation programs.
Example, a patient who could correctly repeat 40 out of 50 words presented would have 80% speech recognition. Because speech is a complex and continually varying signal requiring multiple auditory discrimination skills, it is not possible to repeat accurately.