Response-modifying acoustic couplers for hearing aids

An acoustic coupler for use between an output port of a hearing aid unit and an earmold or the like at the entrance to the ear of a wearer and for obtaining a predetermined frequency response characteristic related to the needs of the wearer, said acoustic coupler comprising:

• hollow housing means, input coupling means at one end of said hollow housing means for coupling to said output port of said hearing aid unit, output coupling means at an opposite end of said hollow housing means for coupling to said earmold, said hollow housing means providing a first chamber therewithin, acoustic elements within said hollow housing means having certain acoustic characteristics and arranged for coupling of said first chamber to said output coupling means, a wall portion within said hollow housing means disposed adjacent said output port of said hearing aid unit and between said output port and said first chamber, and means within said hollow housing means defining a first passage having an input end coupled to said output port of said hearing aid unit and extending through said wall portion and to an output end coupled to said first chamber and to said output coupling means, said passage being elongated and having a cross-sectional size and a volume which are small in relation to those of said first chamber to provide an acoustic element having a relatively high acoustic inertance while said first chamber provides an acoustic element having a relatively high acoustic compliance, said relatively high acoustic inertance of said first passage and said relatively high acoustic compliance of said first chamber cooperating with said acoustic characteristics of said acoustic elements to form an acoustic network which cooperates with said hearing aid unit and said earmold to obtain said predetermined response characteristic related to the needs of the wearer.