The frequency response is one of the most misused specifications of an audio system.
There are two steps in creating sound your patient hears. The first is connecting an audio input to the system. This input is an electrical input, NOT an acoustic input. Unfortunately the frequency response of the input is often quoted as the response of the system.
The second part of the system is the sound coming out of the headset to the patients' ears. Because of natural attenuation in the speakers system and pneumatic headset, this is ALWAYS MUCH LESS than the input.
Although the frequency response of the output is much less and the input, we have a solution! Ask about adding a calibrated equalizer to your MRI audio system.