"Calculate Frequency Spectrum" to determine the input tone frequency

There are many tutorials out there on creating frequency visualisations but none seem to address the actual frequency bands being displayed. i.e. What is the central frequency or the frequency band of each part of the analised spectrum?

So to clarify: The variable “Spectrum Width” in “Calculate Frequency Spectrum” seem to break up the audio spectrum into bands. What it doesn’t explain is: “What is the total Spectrum?” (20 to 20?) and “How is the spectrum divided based on this value?”

I generated pure tones at various frequencies as the input audio and played with the variables to see if this function could provide the correct answer. I assume the correct answer would be the array index wherever the max value occurs. So, to push the limits, I made the Spectrum width 19980 (20kHz - 20 Hz) hoping for a direct hit but it didn’t work. Testing with some other frequencies seems to indicate the spectrum is divided on a log scale. Which is great and matches the expectations of usual audio frequency analisys. But still doesn’t help in understanding the result.

Can anyone help me interpret the “Calculate Frequency Spectrum” array and explain if the actual frequency values can be determined?