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Masking

Telephones are often operated in noisy locations.33 A study of the interfering effect of all the complex noises would be a large undertaking. The present discussion will be limited to the masking effects of pure tones.

In making these masking tests,21 the masking tone was held at a constant intensity level, and the intensity level of the masked tone was gradually increased until it was just perceptible. This level in decibels to which the masked tone must be raised over that necessary without the presence of the masking tone is termed the threshold shift. Typical masking curves are shown in Fig. 19.

masking effect of pure tones
Figure 19. Masking effect of pure tones. Masking tone 1200 cycles, at 20, 40, 60, 80, and 100 db above threshold value. (Courtesy Bell Telephone Laboratories and D. Van Nostrand Company.)


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Last Update: 2011-05-30