You can download an app for Mac OS X for free, and it can be used to aid practice.
Handbook in accordion notation
Authors: Geir Draugsvoll and Erik Højsgaard.
The many aspects of aural training in this book by Erik Højsgaard have been inspired by his deep insight into western music and its thousand-year-old traditions. Written with clarity that allows for rhythm and polyphony to be presented in an understandable form, Højsgaard's book is both musical and entertaining. There is no doubt that one gains new insights and musical joys after working through the book's exercises.
Danish professor and composer Per Nørgård writes:
Rhythm · Advanced Studies