How much more are thresholds measured in SPL than their counterparts in HL according to ANSI standards?

The correct choice of 20 dB reflects the standard conversion between sound pressure level (SPL) and hearing level (HL) as outlined by ANSI (American National Standards Institute) standards.

Thresholds in HL are referenced to the average threshold of hearing for young, normal-hearing individuals, while SPL involves a measurement of sound pressure levels in the environment. The standard stipulates that the average threshold of hearing is approximately 20 dB SPL. Thus, to convert thresholds from HL to SPL, you typically add this 20 dB to the HL value.

For instance, if a person has a hearing threshold of 0 dB HL (which means their hearing is normal according to the standard), this corresponds to about 20 dB SPL. Therefore, understanding this conversion is crucial for accurately interpreting hearing test results and ensuring consistent communication of hearing levels among professionals in audiology and hearing aid fitting practices.