Exercise: Using FFT, estimate the DTMF Tones in the given dialtone.wav file. The signal has a sampling rate of 8 kHz (fs = 8000 Hz). There are 4 consecutive DTMF signals of equal duration (1000 sample/tone). You can read the wav file using audioread function in Matlab. You need to identify the corresponding 4-digit dialed number (XXXX). Show all your work and plot necessary graphs. Summary: A DTMF signal consists of the sum of two sinusoids - or tones - with frequencie taken from two mutually exclusive groups. Each pair of tones contains one frequency oft low group (697 Hz, 770 Hz, 852 Hz, 941 Hz) and one frequency of the high group (1209 Ha 1336 Hz, 1477Hz) and represents a unique symbol. 1209 HZ 1336 Hz 1477 HZ ABC 2 1 1 DEF 3 697 HZ 1 1 1 GHI 4 1 1 JKL 5 770 HZ 1 1 MNO 6 TUV PRS 7 1 . 1 1 WXY 9 852 HZ 1 8 1 1 941 Hz 0 # Example: The following is a DTMF signal in continuous time domain x(t) = sin(2*pi*f_low*t) + sin(2*pi*f_high*t) choosing f_low = 697 Hz and f_high = 1209 Hz, you have the dial-tone for symbol {1}