An accessory office or studio shall not occupy more space than the equivalent of 1/3 of the area of one floor of the dwelling in which such office or studio is used; there shall be no display or advertising on the premises in connection with such use, except a professional nameplate; no assistants, whether paid or not, shall participate in such use, except that one assistant may be employed if the nature of the profession is such as to require an assistant; and any such musician's or sculptor's studio shall be equipped and used in such manner that sounds therefrom are not unduly annoying to other persons or nearby premises or public places.