Example 2. In the previous example, the low-frequency for- mants have been considered. However, di ﬀ erent frequency regions can be used. Thus, the procedure is also tested for watermark modeled according to the middle-frequency formants. The detection results are given in Figure 5(a) ( f max = 4 kHz and L = 32). The ratio between detector responses for right key and wrong trials is lower than in the previous example, with low-frequency formants, but still satisfactory. The obtained SNR is 28 dB. In addition, the middle frequency formants of a signal with f max = 11.025 kHz have been considered. The results of watermark detection are given in Figure 5(b) (L = 32, and SNR = 32 dB). Extended frequency range enables more space for watermarking. Thus, it allows embedding watermark with lower strength, providing higher SNR.