Why are hospitals so noisy?

There are two main reasons for this. Firstly, equipment alarms, monitors, ventilation and people in constant movement are sources of the problem.

Secondly, hard and easy to clean surfaces make up powerful echo chambers for the noise to bounce around in.  

Are poor room acoustics a common problem in hospitals?

According to researchers at Johns Hopkins University, noise levels in hospitals throughout the world have been increasing by about 0.4 decibels per year since 1960. Their findings indicate that average daytime hospital sound levels on a global basis have risen from 57 to 72 decibels since 1960 and that hospital noise at night has gone up from 42 decibels to 60 decibels.

According to the report from Johns Hopkins, current sound levels are now sufficiently high to be a concern to patient safety.

Do I have to chose between a high absorption class and cleanability?

No you don't have to choose between a high absorption class and high cleanability! Ecophon has developed a wide hygiene range of products that fit various demands of cleanability and still fulfill absorption class A.