audioXpress Magazine      February 2022

  audioXpress remains the authority on audio and reproduced sound by connecting manufacturers and distributors with developers, buyers and consultants around the globe! It's readers are the audio product designers, consultants, integrators, DIY enthusiasts, opinion leaders and your best customers. All of them agree that the coverage of trending topics, unique in the audio industry, make audioXpress a must read.

Every month, audioXpress combines the best educational articles on topic such audio electronics, speaker and headphone design, amplifiers (from tube to Class D), acoustics, practical test and measurement, audio engineering praxis, and standards. audioXpress provides inside stories on new audio developments, on R&D Stories, the most complete objective reviews of innovative products and software, and selects some of the best DIY audio projects from worldwide experts.

From The Editor's Desk
4 From the Editor's Desk
Microphones, Haptics, And The Metaverse
Some notable progress is described in this edition.
Editorial By J. Martins

5 Client Index

Features
24 On the Edge
TinyML and Voice Recognition Technology Are Transforming Industries
By Vikrant Singh Tomar
Consumers increasingly expect voice-enabled
devices, such as home assistants or wearables, to
operate offline and in a secure manner no matter
the environment. Rising demand for portable, light
footprint voice recognition devices is fueling a growth
of the tiny machine learning (TinyML) field. This
article explains the impact for embedded voice and
the overall audio industry.

36 Haptic Devices for Augmentation, Entertainment, And Wellness
By Mike Klasco
The music and the auditory world encompass not
only airborne sound energy but also structure-borne
energy, which is perceived by our haptic senses. This
article discusses our ability to interact with the world
through vibration and touch and the role of haptic
perception in our lives.

46 A High-Quality MM Phono, Line, And Headphone Amplifier
By George Ntanavaras
In this project article, the author describes the
design and construction of a phono preamplifier for
moving magnet (MM) cartridges and a line/headphone
amplifier with two additional inputs and volume
control, which he calls the PhL-100.

56 Build a Current Feedback Headphone Amplifier
By Brian Bylenok
Inspired by notable current feedback amplifier
projects previously published by audioXpress, the
author proposes a refined headphone amplifier design
with very low noise and very low distortion that
resulted from methodical experimentation.

Market Update — Microphones
8 From XLR to USB
The Evolving Microphone Market
By J. Martins
The magazine's annual update of microphone technology
addresses the latest products and trends. Traditionally
a market targeting musicians, podcasters, and creatives
 — product segments that all continue to see strong
demand — microphones are increasingly used to
capture voice and our surroundings, and becoming
an essential component in all audio product designs and
our daily lives.

Columns
Sound Control
30 Quantification of Speech Intelligibility
By Richard Honeycutt
In this article, our columnist discusses the history of
speech intelligibility rating systems and the measurement
techniques that evolved into today's international standards.

Hollow-State Electronics
62 Tube Power Amps Have Classes
By Richard Honeycutt
Richard Honeycutt discusses the distinctive features
of various amplifier circuits and what characterizes them as
Class A, Class B, Class C, Class D, Class AB1, and Class AB2.

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