Internal speaker

Adafruit Circuit Playground Express
1

I am connecting a 40khz transducer to A0 and have it working. I have two questions

  1. Can I disable the internal speaker thru software. I was able to disable by wiring D11 to ground
  2. I am generating a 40 kHz tone thru the music option, yet I only measure a max of 19khz
2

Unfortunately with D11 grounded the CPX won’t boot. Need some direction