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The process of determining the decibel level of a specific frequency using FFT involves the following steps:

1. Collect the data: This involves recording the sound or acquiring a digitized signal of the sound that you want to analyze.

2. Convert the signal to the frequency domain using FFT: This involves using the Fast Fourier Transform algorithm to convert the signal from the time domain to the frequency domain.

3. Identify the specific frequency: Determine the frequency range of interest and locate the bin or bins that correspond to that frequency.

4. Calculate the power level: Read the amplitude value of the corresponding bin (or bins) and square it to obtain the power level.

5. Calculate the decibel level: Convert the power level to decibels using the formula: dB = 10 × log10(P/Pref), where “P” is the power level and “Pref” is the reference power (usually 1 milliwatt or 1 picowatt).

6. Interpret results: The final decibel level indicates the strength of the sound at the analyzed frequency.