Uncomfortable Loudness Levels (UCL)
Uncomfortable loudness level (UCL), also called loudness discomfort level (LDL), is the sound intensity at which a person finds amplified sound uncomfortably loud. It is measured in decibels hearing level (dB HL) and represents the upper boundary of a person's comfortable hearing range. The range between a person's hearing threshold (the softest audible sound) and their UCL is called the dynamic range.
UCL measurement is an important component of hearing aid fitting. The hearing aid's maximum output level must be set below the UCL to prevent sounds from being amplified into an uncomfortable or painful range. Wide dynamic range compression (WDRC) in modern hearing aids is specifically designed to keep loud input sounds within the wearer's dynamic range. For people with loudness recruitment, which is common in sensorineural hearing loss, the dynamic range is compressed, meaning the gap between threshold and UCL is smaller than normal, and careful fitting is required to keep all sounds within the comfortable zone.
UCL is also measured as part of cochlear implant programming, where the maximum current level (C-level) delivered by each electrode must be set to a comfortable limit for that user. Measuring UCL accurately requires the cooperation of the patient and clear instructions about the difference between a sound being just loud and being uncomfortably loud.
