Get creative with office partitions to deaden sound and private privacy. Place height adjustable desks on each side for an inexpensive solutions.
From an ergonomic and productivity standpoint, employees are more productive when sound is controlled. It should not be too quiet, or too noisy. The majority of open offices are around 40-60dB which can create performance issues. (i.e. a noisy highway is 85 DB) In addition, what may bother one employee will not bother another person in the same setting.