To my knowledge this is working as designed and is governed by international / national laws.
There are parameters that can manually adjust the phone's volume levels but you would need to raise a ticket via your Polycom reseller in order for our support team to advise you on the levels and make you aware that changing these may violate above laws.
Please ensure to provide some feedback if this reply has helped you so other users can profit from your experience.
Polycom Global Services
Notice: This community forum is not an official Poly support resource, thus responses from Poly employees, partners, and customers alike are best-effort in attempts to share learned knowledge. If you need immediate and/or official assistance please open a service ticket through your proper support channels. Please also ensure you always check the VoIP , Video Endpoint , Skype for Business , PSTN or RPM FAQ's