•If a signal that exceeds the Nyquist sampling rate, it will be incorrectly “aliased” to the wrong frequency in the digital domain.
–This is not common on commercially available audio equipment since they include front end filters.
–For this reason, the digital domain is considered to have a periodic frequency domain.
The valid range is from
–fs/2 to fs/2. Outside this are images.
•If a signal manipulation in the digital realm causes frequencies to be adjusted or shifted, they will also be aliased to other frequencies
•When the signal is created via a D/A, it must be filtered to reduce the out of band energy.
These out of band signals
are called “images”.