Several have commented here that the speaker audio quality of the iPad Pro M4 is inferior to earlier models. Given that this model is thinner than its forebears, the speakers and associated bass resonators are smaller - and as such, audio quality may seemingly suffer.
If you are concerned, you might be best advised to seek assistance directly from Apple Support. You can contact the Support Team using the Support link at top-right or bottom-left of this page.
Alternatively, you can initiate and manage your support cases from Apple devices using the excellent Apple Support App. If not already installed, the App can be downloaded from the App Store:
https://apps.apple.com/app/apple-support/id1130498044
You might also visit the Genius Bar at your local Apple Store or Apple Authorised Service Provider (AASP) - where the technicians will be able to hands-on test and assess your iPad. If a fault is identified, you'll be in the best possible place to explore your available options:
Genius Bar Reservation and Apple Support Options - Apple