I'm building a PCB design that will trigger certain events when the onboard microphone picks up specific sounds outside of the range of human hearing. The desire is to be able trigger events remotely without a wireless radio connection, for example at events with large crowds of people, and this intuitively seemed like it might be a robust method.

Would anyone be able to share any insights in to things I'd need to consider? For example if is it better to go lower or higher frequency than the human range? Or are there ranges that would be aggrevating to dogs or other animals? Etc etc

Thanks for your help!

I'm building a PCB design that will trigger certain events when the onboard microphone picks up specific sounds outside of the range of human hearing. 

The desire is to be able trigger events remotely without a wireless radio connection, for example at events with large crowds of people. This intuitively seemed like it might be a robust method.

Would anyone be able to share any insights in to things I'd need to consider? For example, is it better to go lower or higher frequency than the human range? Are there ranges that would be aggravating to dogs or other animals? Etc etc