Masking threshold

This threshold depends upon the frequency, the type of masker, and the kind of sound being masked.

In the context of audio transmission, there are some advantages to being unable to perceive a sound.

This requires fewer bits to encode the sound and reduces the size of the final file.

In this situation, it would be necessary to compute the global masking threshold using a high resolution Fast Fourier transform via 512 or 1024 points to determine the frequencies that comprise the sound.

Because there are bandwidths that humans are not able to hear, it is necessary to know the signal level, masker type, and the frequency band before computing the individual thresholds.

Spectrum chart
The spectrum of a 1 kHz tone. A sound will not be heard if it is under the threshold in quiet. This limit changes around the masker frequency, making it more difficult to hear a nearby tone. The slope of the masking threshold is steeper toward lower frequencies than toward higher frequencies, which means it is easier to mask with higher frequency tones.