The hard drive on 7-series recorders generates nearly imperceptible noise levels, and it is the only device with any acoustical noise output on the recorders. Unless one presses his or her ear against the unit they will not be able to hear the drive during operation.
During power-up and power-down there is a very slight drive noise as the drive spins up/down. The noise level is appropriate for the unit to be located in the closest proximity to sensitive microphones within low noise recording spaces. If the drive begins to have a noticeable acoustical whine, its bearings may be failing. It is recommended to back up all audio data and replace the drive. The hard drive is warranted for one year from the date of purchase.
The internal hard drives of the recorders can be replaced with Solid State Drives (SSD). There are many advantages to installing an SSD including silent operation. Click here for more information on SSD and the 722/744T. Click here to find out more about the 788T-SSD.