In addition to what others have said about distraction being more than just noise, this idea runs directly counter to the "official" reason for open plans: free

In addition to what others have said about distraction being more than just noise, this idea runs directly counter to the "official" reason for open plans: free flow of information and spontaneous communications. By necessity those make an open plan noisy. In fact, it creates a horrible contradiction: you are supposed to be able to simultaneously block out all this shit, but still pay attention for those moments of serendipity wherein you can interject something useful. The vast majority of knowledge workers can't work like that.