I believe that Phonak will be going into this field also with the Naida.
I believe they also have a patent. See below:
US 7,248,711 B2 Method for frequency transposition and use of the method in a hearing device and a communication device Silvia Allegro, Oetwil am See (Switzerland); Olegs Timms, Zurich (Switzerland); Adam Hersbach, The Patch (Australia); Hugh McDermott, Mt. Macedon (Australia); and Evert Dijkstra, Fontaines (Switzerland) Assigned to Phonak AG, Stafa (Switzerland) Filed on Mar. 05, 2004, as Appl. No. 10/794,912. Application 10/794912 is a continuation in part of application No. 10/383142, filed on Mar. 06, 2003, abandoned. Prior Publication US 2004/0264721 A1, Dec. 30, 2004 Int. Cl. H04R 25/00 (2006.01) U.S. Cl. 381—316 [381/317; 381/320] 24 Claims 1. A method for frequency transposition in a hearing device or in a communication device, respectively, comprising the steps of transforming an acoustical signal into an electrical signal and transforming the electrical signal from time domain into frequency domain to obtain a spectrum, applying a frequency transposition to the entire spectrum in order to obtain a transposed spectrum as an output signal, wherein the frequency transposition is at least partially defined by a nonlinear frequency transposition function and wherein the electrical signal is not superposed with the output signal.
This aside, frequency transposition is a very difficult thing to accomplish and make sounds “natural” at the same time. In fact, it may be impossible to make sounds “natural” or as you remember them. Yet, if the goal is to improve speech discrimination, which should be the goal, then whatever helps you to understand speech better should be the route taken, with less emphasis on the “naturalness” that we focus a lot on in traditional fittings.