Note about this expanded version (December 2021)Substantially updated with a new chapter on the use of Octave for DSP applications. The new chapter aims to bring together many of the threads of discussion from earlier chapters all under the umbrella of the DSP workflow process. A large number of new diagrams are added to aid in understanding the concepts. In detail, the book describes what is meant by a digital signal and illustrates it with examples of real audio signals. After introducing the notion of a signal and what it looks like, we then explain how to view, modify, and review signals using DSP. No mathematical background is needed. The book can be read in its entirety or the reader can follow along and run the examples in parallel. Running the examples is easy using the open source Audacity application. The examples include how to execute a simple low-pass filter and then verify the result. Verification of signal modification is really important in DSP. This is because it is all too easy to corrupt a signal, e.g., if you are experimenting with some handcrafted code and inadvertently write a bug. For this reason, the book includes a description of a simple DSP process. Another common DSP problem is signal visualization. Graphical tools, such as, the signal screens in Audacity, may not give you sufficient detail when examining some part (or all) of a given signal. Usually, this is Mother Nature giving you a hint that a change in perspective is required. For this, it may be beneficial to change to using some other tooling element. The book describes the need for a flexible perspective on the part of the DSP practitioner.