ihcenvelope(insig,fs,methodname) extract the envelope of an input signal insig sampled with a sampling frequency of fs Hz. The envelope extraction is performed by half-wave rectification followed by low pass filtering. This is a common model of the signal transduction of the inner hair cells.
The parameter methodname describes the kind of low pass filtering to use. The name refers to a set of papers where in this particular method has been utilized or studied. The options are
|'ihc_bernstein'||Compute the Hilbert envelope, compress the envelope by raising it to the power .2, combine the envelope with the original fine-structure, half-wave rectify it, square it and low-pass filter it with a cut-off frequency of 425 Hz. This method is defined in Bernstein (1999). Note that this method includes both a compression and an expansion stage.|
|'ihc_breebaart2001'||Use a 5th order filter with a cut-off frequency of 770 Hz. This method is given in Breebaart (2001). Page 94 in Breebart's thesis.|
|Filter order for the Breebaart filter, default: 5.|
|'ihc_dau1996'||Use a 1st-order Butterworth filter with a cut-off frequency of 1000 Hz. This method has been used in all models deriving from the original 1996 model by Dau et. al. These models are mostly monaural in nature.|
|'ihc_king2019'||Use a 1st-order Butterworth filter with a cut-off frequency of 1500 Hz.|
|'hilbert'||Use the Hilbert envelope instead of the half-wave rectification and low pass filtering. This is not a releastic model of the inner hair envelope extraction process, but the option is included for completeness. The Hilbert envelope was first suggested for signal analysis in Gabor (1946).|
|'ihc_lindemann'||Use a 1st order Butterworth filter with a cut-off frequency of 800 Hz. This method is defined in the Lindemann (1986a) paper.|
|'ihc_meddis'||Use the Meddis inner hair cell model.|
|'minlvl'||Set all values in the output equal to minlvl. This ensures that the output is non-negative and that further processing is not affected by unnaturally small values. The default value of  means to not do this.|
|'dim',d||Work along dimension d.|
L. Bernstein, S. van de Par, and C. Trahiotis. The normalized interaural correlation: Accounting for NoSπ thresholds obtained with Gaussian and l̈ow-noisem̈asking noise. J. Acoust. Soc. Am., 106:870--876, 1999.