# Audio Steganalysis Estimation with the Goertzel Algorithm
## 3 Performance Evaluation
### Frequency Analysis Decomposition
#### 3.4.3 Goertzel Vector Audio Comparison  
To verify and validate the presence of unexpected signals, we illustrate the differences between the graphs obtained from the original vector and the vectors with possible additional information. In Figure 14a-e, we show the variations obtained between the audio samples in Figure 14. If no variation exists between the spectrums, an amplitude of 0 is shown in each of the frequency components of the original audio and the stegoaudio. Figure 13: Comparative graphic of the magnitude spectrum of the original audio channels and the possible stegoaudio. **(**a**) Comparison of the magnitude spectrum of the left channel of the original audio and the possible stegoaudio in analysis. (**b**) Comparison of the magnitude spectrum of the right channel of the original audio and the possible stegoaudio in analysis. (**c**) Comparison of the magnitude spectrum of the left channel of the original audio and the possible stegoaudio in analysis. (**d**) Comparison of the magnitude spectrum of the right channel of the original audio and the possible stegoaudio in analysis. (**e**) Comparison of the magnitude spectrum of the left channel of the original audio and the possible stegoaudio in analysis. (**f**) Comparison of the magnitude spectrum of the right channel of the original audio and the possible stegoaudio in analysis. Nonetheless, each of the channels exhibits variations. Some hidden information present in the audio is not perceptible by human hearing, which is common when the concealment procedure of diverse steganography algorithms is applied to audio. Test 1. The difference graphs are shown with Goertzel analysis between the original file and the supposed stegoaudio (audio files only). To confirm the results obtained from the Goertzel algorithm shown in Figures 11 and 12, we calculate the difference between the original audio vectors and the possible stegoaudios. Figure 14: Graphic of the differences between the frequency spectrum of the original audio channels and the possible stegoaudio. (**a**) Difference between the original audio spectrum and the possible stegoaudio of the right channel in analysis. (**b**) Difference between the original audio spectrum and the possible stegoaudio of the right channel in analysis. (**c**) Difference between the original audio spectrum and the possible stegoaudio of the right channel in analysis. (**d**) Difference between the original audio spectrum and the possible stegoaudio of the right channel in analysis. (**e**) Difference between the original audio spectrum and the possible stegoaudio of the right channel in analysis. (**f**) Difference between the original audio spectrum and the possible stegoaudio of the right channel in analysis. Figure 14 shows these differences in both the right channel and the left channel, displaying the detected tones (fingerprints) more precisely. Test 2. Figure 15 shows the results obtained from the difference in audio signals between the original file and the supposed stegoaudio (text and image files). Figure 15: Graphic of the differences between the frequency spectrum of the original audio channels and the possible stegoaudio. (**a**) Difference between the original audio spectrum and the possible stegoaudio of the right channel in analysis. (**b**) Difference between the original audio spectrum and the possible stegoaudio of the right channel in analysis. (**c**) Difference between the original audio spectrum and the possible stegoaudio of the right channel in analysis. (**d**) Difference between the original audio spectrum and the possible stegoaudio of the right channel in analysis. (**e**) Difference between the original audio spectrum and the possible stegoaudio of the right channel in analysis. (**f**) Difference between the original audio spectrum and the possible stegoaudio of the right channel in analysis. In Figure 15, we can see the differences between the original audio vectors and the possible stegoaudios attacked with images. In Figure 15a,c,e, we observe the detected frequency tones.