Patent ID: 7653534

Claim:
An apparatus for determining a type of chord underlying a test signal, the type of chord being defined by an occurrence of predetermined frequencies in a frequency range of the test signal, and the predefined frequencies in the frequency range of the test signal corresponding to tones in a predetermined spectral margin, wherein a first type of chord has at least one predefined significant tone in the spectral margin and wherein a second type of chord has a second predefined significant tone in the spectral margin, wherein the first significant tone differs from the second significant tone, and wherein the apparatus for determining comprises: a provider for providing a reference vector for the type of chord from a plurality of different reference vectors, the reference vector comprising a plurality of reference vector elements associated with one tone, respectively, in the spectral margin, and wherein at least one significant reference vector element is provided for each reference vector for a significant tone of an associated type of chord; a provider for providing a test signal vector from the test signal, wherein the test signal vector comprises a plurality of test signal vector elements associated with one tone, respectively, in the spectral margin, wherein a test signal vector element is dependent on whether the tone associated with the test signal vector element occurs in the test signal, wherein the provider for providing a test signal vector is configured to allocate a value of one to a test signal vector element if the tone corresponding to the test signal vector element has an amplitude value which exceeds a predetermined threshold value, and wherein the provider for providing a test signal vector is configured to allocate a value of zero to the test signal vector element if the tone which corresponds to the test signal vector element has an amplitude value falling below the predetermined threshold value; and a comparator for comparing the reference vector with the test signal vector, the comparator being configured to compare the reference vector with the test signal vector or with versions of the test signal vector which are cyclically shifted by various shift values in the frequency range, in order to obtain various comparative results allocated to the test signal vector or shift values in order to determine the type of chord on the basis of an extreme comparative result and of the shift value associated with same.