What is 'non-irritating' to the people at one table might be extremely irritating to those at another, and possibly most unpleasant for someone with synaesthesia affecting taste, such as certain voices or harmonies tasting of suet pudding, or gooseberries, or worse. And what, to people with normal hearing, shields one table from hearing the conversation of another, might shield people with slightly impaired hearing from the conversation at their own table.