Introduction to Digital Signal Processing: Computer Musically Speaking (review)

In his introductory book on signal processing, entitled Introduction to Digital Signal Processing: Computer Musically Speaking, Tae Hong Park focuses on inculcating in his readers solid conceptual foundations and intuition by confronting the mathematical fundamentals while going to great lengths to answer the question "why," not just "how." Students tackling the subject for the first time will appreciate the attention to the reasons behind acoustic phenomenon or the creative purpose for using certain signal processing techniques, versus merely learning how to solve cookie-cutter problems.

Mr. Park starts by setting a familiar conversational tone, introducing basic psychoacoustic concepts surrounding the limitations of human hearing. This relaxed style warms up the reader in preparation for the subsequent chapters on sampling theory, time-domain processing techniques, sinusoidal and frequency modulation. In the study of the time domain, in addition to presenting the basic concepts like overlap and add, windowing and auto-/cross-correlation, Mr. Park takes pains to contextualize these concepts from the perspective of two classic applications, granular and waveshaping synthesis. Several common audio effects for dynamics processing that one might find in any recording studio or digital audio workstation (DAW), like the compressor, expander, and distortion are also covered, putting a practical angle on fundamental time-domain concepts like amplitude envelope, windowing, and Root-Mean-Square (RMS). Additionally, there is a short section where common modulation effects like echo/delay, chorus, and flanging are examined with a brief history and some examples.

Linear time-invariant (LTI) systems are reviewed next, along with impulse responses and finite impulse-response/ infinite impulse-response (FIR/IIR) filters. Mr. Park's treatment of this material unfurls in a manner similar to much of the traditional literature on signal processing. This sets up vital groundwork for the introduction, in subsequent chapters, to the frequency domain and concepts like frequency response and the Z-Transform. When the reader reaches the chapters on filter design and the Fourier transform, Mr. Park cleverly revisits aliasing, up/down sampling, convolution, and windowing, subtopics covered in the previous chapters. This time, these concepts are reinforced from the perspective of the frequency domain. This method of revisiting concepts from various angles and linking ongoing "conceptual themes" throughout the book is critical for students looking to build strong fundamentals.

The last chapter takes a rigorous look at spectral analysis, voice-coding techniques, and their applications. Mr. Park surveys algorithms for estimating the fundamental frequency of a signal including inverse-comb filtering, cepstrum analysis, and harmonic product spectrum. The section on vocoders (voice coders) starts with a short history lesson about the channel vocoder and its use during World War II before exploring filter banks, voiced/unvoiced analysis, linear predictive coding (LPC), and the phase vocoder. The final section of the book looks into the future with an overview of the state of the art of research topics in computer music and signal processing. Commencing with salient feature extraction, Mr. Park covers many important MPEG-7 low-level descriptors, like spectral (envelope, centroid, flux, log spread), attack time, and temporal centroid, as well as concepts like shimmer and jitter. The section onmusic information retrieval (MIR) tackles applications such as query-by-humming, rhythm analysis, and automatic timbre recognition. The book concludes with a review of feature modulation synthesis, a set of analysis/synthesis techniques that allow composers to control perceptually pertinent aspects of sound. The appendix addresses the mathematics of tuning systems, the nonlinearities of pitch perception, and includes a handy anthology of several musical and psychoacoustic scales like equal temperament, just intonation, and the Mel and Bark scales.

In every chapter, alongside the mathematics, Mr. Park offers a distinctly practical means to absorb the theoretical concepts in the form of handy "need to know" sections and runable Matlab code. In fact, all...