What does 'dB SL' measure?

The term 'dB SL' stands for "decibels above sensation level." It specifically measures the intensity of a sound relative to an individual's hearing threshold at a particular frequency. Essentially, it quantifies how much louder a sound is compared to the threshold of hearing for that specific person. For example, if a person's threshold for a certain frequency is 20 dB SPL (sound pressure level), a sound measured at 40 dB SL would be perceived as being 20 dB louder than their threshold for that frequency.

This concept is especially important in audiology and hearing instrument fitting as it allows professionals to tailor their evaluations and interventions based on individual hearing sensitivities. The emphasis on individual thresholds is what differentiates dB SL from other measurements like sound pressure levels or standards that do not take personal hearing ability into account, which is why this measure is critical in clinical settings.

In contrast, measures such as sound pressure levels relate more broadly to ambient noise and do not focus on individual thresholds, while standard measurement for all frequencies might not reflect personalized hearing abilities. Additionally, the threshold of pain is a fixed point on the scale of hearing sensitivity, whereas dB SL is variable and specific to each person’s threshold.