A computer-implemented method for conducting a cross frequency simultaneous masking (xF SM) test, the method comprising: generating a signal probe and a masker probe, wherein a center frequency of the signal probe (Fs) and a center frequency of the masker probe (Fc) are separated by a first fixed frequency ratio (r), wherein the signal probe and masker probe are provided to a user of an audio output device as an auditory stimulus; for a given frequency range, generating a first xF SM curve by: sweeping the signal probe and the masker probe across the given frequency range while maintaining the first fixed frequency ratio (r) between the signal probe and the masker probe; maintaining the masker probe at a pre-determined masker amplitude; adjusting (303, 304) the amplitude of the signal probe in response to a series of user inputs, wherein the series of user inputs comprises user responses indicating the user's perception of the auditory stimulus; and interpolating the series of user inputs to generate the first xF SM curve; and for the given frequency range, generating a second xF SM curve by: sweeping the signal probe and the masker probe across the given frequency range while maintaining a second fixed frequency ratio (r) between the center frequency of the signal probe (Fs) and the center frequency of the masker probe (Fc); adjusting (303, 304) the amplitude of the signal probe in response to a second series of user inputs; and interpolating the second series of user inputs to generate the second xF SM curve, wherein the second fixed frequency ratio (r) is different than the first fixed frequency ratio (r). generating a signal probe and a masker probe, wherein a center frequency of the signal probe (Fs) and a center frequency of the masker probe (Fc) are separated by a first fixed frequency ratio (r), wherein the signal probe and masker probe are provided to a user of an audio output device as an auditory stimulus; for a given frequency range, generating a first xF SM curve by: sweeping the signal probe and the masker probe across the given frequency range while maintaining the first fixed frequency ratio (r) between the signal probe and the masker probe; maintaining the masker probe at a pre-determined masker amplitude; adjusting (303, 304) the amplitude of the signal probe in response to a series of user inputs, wherein the series of user inputs comprises user responses indicating the user's perception of the auditory stimulus; and interpolating the series of user inputs to generate the first xF SM curve; and for the given frequency range, generating a second xF SM curve by: sweeping the signal probe and the masker probe across the given frequency range while maintaining a second fixed frequency ratio (r) between the center frequency of the signal probe (Fs) and the center frequency of the masker probe (Fc); adjusting (303, 304) the amplitude of the signal probe in response to a second series of user inputs; and interpolating the second series of user inputs to generate the second xF SM curve, wherein the second fixed frequency ratio (r) is different than the first fixed frequency ratio (r). sweeping the signal probe and the masker probe across the given frequency range while maintaining the first fixed frequency ratio (r) between the signal probe and the masker probe; maintaining the masker probe at a pre-determined masker amplitude; adjusting (303, 304) the amplitude of the signal probe in response to a series of user inputs, wherein the series of user inputs comprises user responses indicating the user's perception of the auditory stimulus; and interpolating the series of user inputs to generate the first xF SM curve; and for the given frequency range, generating a second xF SM curve by: sweeping the signal probe and the masker probe across the given frequency range while maintaining a second fixed frequency ratio (r) between the center frequency of the signal probe (Fs) and the center frequency of the masker probe (Fc); adjusting (303, 304) the amplitude of the signal probe in response to a second series of user inputs; and interpolating the second series of user inputs to generate the second xF SM curve, wherein the second fixed frequency ratio (r) is different than the first fixed frequency ratio (r). sweeping the signal probe and the masker probe across the given frequency range while maintaining a second fixed frequency ratio (r) between the center frequency of the signal probe (Fs) and the center frequency of the masker probe (Fc); adjusting (303, 304) the amplitude of the signal probe in response to a second series of user inputs; and interpolating the second series of user inputs to generate the second xF SM curve, wherein the second fixed frequency ratio (r) is different than the first fixed frequency ratio (r).