This article is based on the "Application of MATLAB in speech signal analysis and synthesis," the reading experience, to thank.
The masking effect is to make a sound that can be perceived by a threshold A due to the occurrence of another sound to improve the phenomenon B, wherein B is a masking sound, the sound A is masker.
We must first understand what is perceived threshold, a personal understanding is the lowest sound pressure level the human ear can perceive. Pure tone masking pure tones example (shown below), can be clearly found that the audible threshold curve, the sound in the absence of masking, the human ear can hear the sound A, a sound B, and a minimum sound pressure level of the sound C a, b, and c. When the masking sound occurs, when the human ear can hear the sound A, the sound B, and a minimum sound pressure level increase C to sound a ', b' and c '. FIG masking threshold at the masking curve indicates, the sound A, a sound B, and C be the sound perceived by the human ear the minimum sound level. Obviously, when masker appears, you could hear three voices become not hear.
In general, the stronger masker, the masker frequency sound is masked by the closer, the more obvious the masking effect, when the two frequencies are the same, the maximum masking effect.
Discussed above is the case and the masker masker occur simultaneously, when both are not occur simultaneously, there is a masking effect, called short masked. Short masking divided into two cases, the first case is when the masking sound and the masking sound exist, after masking the sound suddenly disappeared, its role will continue 0.5-2s masking long, which is due to storage of human ears due. Another situation is masked by the sound comes first, separated within 0.05 ~ 0.2s, the masking sound occurs immediately, it will also play a role in masking the masking sound that the human ear can not detect the start to finish masked there is sound.
There is a common masking effect of noise masking pure tones. This method uses a center frequency is f, △ f bandwidth of white noise masking a pure tone of frequency f. Just can mask a narrowband noise bandwidth of the pure tone hearing △ f called critical bands. This phenomenon can be found from the auditory physiological basis. Ear base film may be divided into a number of small portions, each portion corresponding to one frequency group, 20 ~ 22050Hz frequency band may be divided into frequency groups 25 (shown in the following table). Those portions of each sound frequency, evaluate brain is added together, and if they are sounded simultaneously, each may be masked.
Research masking effect, contribute to the understanding and estimation of timbre, loudness and pitch. In speech enhancement and speech coding, using the masking effect of improving the quality of output voice has made great benefits, masking effect can also be used for high-frequency noise from the motor problems of improving the electric car vehicle.
