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082-Engineering-Mathematics-Anthony-Croft-Robert-Davison-Martin-Hargreaves-James-Flint-Edisi-5-2017

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812 Chapter 24 The Fourier transform

f [n]

Scale:

1s

g[n]

Figure24.30

Two audio signals:a2simpulseresponse ofan environment to be simulated, f[n], anda30s

music trackto be processed,g[n]. Bothsignals are sampled atarate of44100 samples per

second.

Figure24.31

The output signalh[n] = f ○∗ gincluding reverb.

EXERCISES24.15.3

1 Thecircular convolution of f[n] = 1, −1,1,3 and

g[n] = 7,2,0,1 wascalculated in Question 1 in

Exercises24.15.2. Verify the convolution theorem for

these sequences.

2 Usecircular convolution and padding with zerosto

obtain the linear convolution of f[n] = 9,0,1 and

g[n] = 5,4,5,2,1.Further, verifythe convolution

theorem forthese sequences.

3 Provethe circular convolution theorem.

Solutions

1 F[k] =4,4j,0,−4j.G[k] =10,7−j,4,7+j 2 45,36,50,22,14,2,1

24.15.4 Linearcross-correlation

The linear cross-correlation of two real sequences f[n] andg[n] is another sequence,

c[n] say, which wedenote by f ⋆g, which isdefined asfollows:

Linear cross-correlation of f[n]andg[n]:

∞∑

c[n]=f⋆g= f[m]g[m−n] forn=...−3,−2,−1,0,1,2,3...

m=−∞

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