Frequency discrimination in quiet and in noise for signals with triangular spectral envelopes.

The just-noticeable-difference in frequency (jndf) for complex signals with triangular spectral envelopes is found to depend on the envelope slope. For shallow slopes (less than 140 dB/oct), jndf increases with decreasing slope. Addition of noise also impairs frequency discrimination within a region of about 20 dB above masked threshold. This is found for both maskers used: a wideband noise and a narrow-band masker which is below the signal in frequency. When wideband noise is used, frequency discrimination of complex signals with shallow slopes deteriorates more rapidly with decreasing signal-to-noise ratio than it does when the signals have steep spectral slopes.