I want to generate inaudible sound waves (above 18kHz) with 48kHz sampling rate using MATLAB.
Generating a sound wave with 18kHz frequency makes it inaudible.
I've inserted the data in the 18kHz band in the frequency domain, converted it into time domain signal.
Then I've duplicated the signal, concatenated it, and played it.
As expected, the played sound was inaudible.
The problem is,
I want to play the inaudible sound with an interval.
(playing sound wave for 1.75ms and having a silence period for 4.17ms repetitively)
Because of the inserted silence period, the concatenated signal is no longer inaudible because new frequency components are added.
How I can transmit inaudible sound with time interval?