2.6.1.5.1 Hearing requirements are identical for Class 1 and Class 3 Certificates. However, they are not in
compliance with the ICAO Standards for Class 1 hearing requirements.
The above is the difference filed by the US regarding the requirement for Class 1 hearing.
There is also a difference filed that US ATPL holders do not meet ICAO medical standards.
Regards,
DFC