No effect on recording with chip ATJ2167 about antispy-jammer HOT 1 OPEN

The point is to use the transducers that have bigger tollerance. Normally available transducers are 25 kHz +/- 1KHz. Therefore the code operates within 24KHz-26KHz frequency range. The source code does FM modulation effect by driving the transducers out of its center frequency in steps while also doing AM type of modulation because if you move out of the center frequency the amplitude of the audio signal gets smaller.
The combination of both techniques FM+AM modulation gives the jamming effect.
IF you want to increase this effect you need to look for the transducers with wider range like 25KHz +/- 2KHz that can operate within 23-27KHz range. You will also need to adapt the code by changing the frequency values respectively.
It is not easy to find such transducers but you may start searching from www.alibaba.com or www.made-in-china.com
Check the datasheets from the suppliers and concentrate on 24mm diameter models.
I have found such on aliexpress.com but I am not sure if it is really 25kHz +/- 2KHz as they state in the description
https://www.aliexpress.com/item/1644918793.html

from antispy-jammer.