Errata

Corrections to the textbook, Hack Audio: An Introduction to Computer Programming and Digital Signal Processing in MATLAB. Code examples posted to the GitHub repository show the following revisions.

Example 6.5: Incorrect variable name. Use this instead:

[x,Fs] = audioread(filename);

Example 6.7: Missing time vector for plot. Include:

Ts = 1/Fs; N=length(sw1); t=[0:N-1]*Ts; t=t(:);

Section 7.3.5 Triangle Wave Additive Synth. Every other harmonic should be multiplied by -1:

$triangle(x) = \frac{8}{{\pi}^{2}} (sin(x) - \frac{1}{9}sin(3\cdot x) + \frac{1}{25}sin(5\cdot x) - \hdots)$

$triange(x) = \frac{8}{{\pi}^2} \sum\limits_{n=1,3,5,...}^{M} \frac{1}{n^2}sin(n\cdot x) \cdot (-1)^{\frac{(n-1)}{2}}$

In Section 8.6: The transformation of linear scales should have these paratheses:

Let: $y = \frac{{m}_{n}}{{m}_{o}}\cdot (x - {\mu}_{o}) + {\mu}_{n}$

Example 9.6: Arrays should be initialized using zeros(N,1), not size(). Substitute:

x = zeros(N,1); y = zeros(N,1);

Figure 11.7: The arrow connecting the multiplication block for $-{a}_{W}$ to the addition block is pointing in the wrong direction. The arrow should point from the multiplication block to the addition block on the feedback path.

Table 13.1: Calculation of bi-quad coefficients. For High Shelf coefficient, ${b}_{1}$ , missing parenthesis, change minus sign to plus sign:

${b}_{1} = -2 \cdot A((A-1) + (A+1) \cdot cos({w}_{0}))$

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