Effects of Different Stimulus Types
Experiments have been carried out to see the different masking effects when using a masker which is either in the form of a narrow band noise or a sinusoidal tone.
When a sinusoidal signal and a sinusoidal masker (tone) are presented simultaneously the envelope of the combined stimulus fluctuates in a regular pattern described as beats. The fluctuations occur at a rated defined by the difference between the frequencies of the two sounds. If the frequency difference is small then the sound is perceived as a periodic change in the loudness of a single tone. If the beats are fast then this can be described as a sensation of roughness. When there is a large frequency separation, the two components are heard as separate tones without roughness or beats. Beats can be a cue to the presence of a signal even when the signal itself is not audible. The influence of beats can be reduced by using a narrowband noise rather than a sinusoidal tone for either signal or masker.
Read more about this topic: Simultaneous Masking
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