Compression Ratio
Also written as: CR — Compression Ratio
The ratio of the change in input sound level to the change in output level in a hearing aid's compression circuit, controlling how amplification varies with loudness.
Full Definition
Compression ratio (CR) in hearing aid technology describes how much the output level changes relative to a given change in input level once compression is activated. A compression ratio of 2:1 means that for every 2 dB increase in input, the output increases by only 1 dB, thereby reducing the dynamic range of the signal to fit within the listener's usable hearing range. Compression ratio settings are a core component of hearing aid fitting reports and are adjusted to accommodate loudness recruitment. Editors reviewing hearing aid fitting documentation should verify that compression ratio values are expressed consistently (e.g., as n:1) and that the associated compression threshold is stated. Conflating compression ratio with gain is a common editorial error.
Usage
Usage note: Always express as a ratio (e.g., 3:1, not '3'). Distinguish clearly from gain, which is expressed in dB, not as a ratio.
In Context
- "A compression ratio of 3:1 was applied in the high-frequency channels to manage the patient's loudness recruitment." — Hearing aid fitting documentation
- "The author incorrectly referred to 'compression gain' when the context clearly described the compression ratio setting." — Manuscript copy-editing note