Mumbai university > Electronics and telecommunication Engineering > Sem 7 > Data compression and Encryption

Marks: 4

Years: May 2016

Frequency/Auditory masking:

• Masking or removing low sensitive frequency component in audible band is called as frequency domain masking. It is also called as equalisation or windowing.

• Frequency masking depends upon frequency.

• It occurs when a sound that we can normally hear is masked by another sound with a nearby frequency.

• Arrow (above diagram) at 8 kHz represents a strong sound space.

• This source raises normal threshold in its vicinity such that the nearby sound 'x' is masked and is inaudible.

• A good lossy audio compression method should identify this case and delete the signal carries pending to sound 'x' since it cannot be heard anyway. This is one way to lossy compression sound.

Temporal masking:

• Temporal masking is defined as process by which redundant data in sound speech like pauses, longer length alphabets like F, S is masked in time domain.

• Disadvantages of Temporal masking:

o Designing of system is complex because of convolution process.

o No specific range of sound in temporal domain.