Audio engineers are usually thought of as being in charge of recording audio signals in a recording studio, but they ply their trade in other ways too. Mixing engineers also work in the recording studio, but rather than capturing audio signals during tracking, their task is to take all of the recorded parts, manipulate their levels and tones, and create a quality musical mix from them. Sometimes the recording engineer and mixing engineer are one and the same, but it's not uncommon for projects to be recorded in one facility and then mixed in another by a different engineer.
Mastering engineers are specialists who take a finished mix and apply the final sheen to it with expert use of EQ and compression. They're in charge of delivering a polished master disc to a record company or artist to be used for mass replication.
Live sound engineers use many of the same audio skills as studio engineers, but their job is to take an array of audio signals and create a listenable audio experience for the audience at a live music venue.
Audio engineering was born with Thomas Edison's introduction of his primitive phonograph in 1877. Although it was effectively a strip of tin foil wrapped around a cylinder, it paved the way for the audio advancements to follow.
In 1925 Bell Labs developed a cutting system that allowed for electric recording on discs, and the same year the first electrically recorded 78 rpm records were made. Around the same time, RCA was developing its soon-to-be legendary ribbon condenser microphones, and new levels of audio fidelity became possible.
The advent of magnetic tape in the late '30s and the further development of high-quality condenser microphones by RCA, Neumann and Shure ushered in new developments in recording and disc cutting, and in 1942 the first stereo recordings were made in Berlin. By the time World War II broke out, magnetic tape had become the recording medium of choice. Multitrack recording followed soon after. Magnetic tape recording held sway in the recording industry until the advent of digital technology in the '80s. At the dawn of the 21st century, computer-based digital recordings became the dominant force in audio recording. What they lost in perceived analog warmth they made up for in functionality and flexibility.
Audio engineers have to be well versed in the technical details of the equipment used in the recording studio, and have an understanding of how these components are routed for the correct signal flow. They need to be adept at choosing microphones and processors for specific recording applications and positioning the microphones for optimum performance. They also, of course, require an intimate knowledge of how to manipulate these and other sound sources via a mixing console to create a well-balanced mix at the mix-down stage. Doing this requires experience in such concepts as equalization (EQ), compression, limiting and all manner of effects processors.
Many accredited learning institutions worldwide have degree programs in the field, such as BS degrees in audio production, but audio engineers may also have a background in electrical engineering. It's also true that a great number of audio engineers work in the industry without any formal training, and often learn in an on-the-job capacity, usually while working as a production assistant in a recording studio. Others take advantage of in-depth online courses in sound engineering (see Resources) to arm themselves with the technical knowledge necessary to apply for in-house studio positions.
While the term "audio engineer" certainly covers a broad range of duties, and the word "engineer" is often associated with the job of planning and designing equipment, today the term is usually used to describe someone who actually operates an array of electronic audio devices, rather than someone who designs them. Although it's still a position that requires a considerable amount of technical knowledge to accomplish, it's also one that has become quite a creative one, where artistic decisions are made in determining how and when to use certain devices. It's here that the lines between production and engineering often get blurred. Indeed, many producers act as their own engineer, and vice versa.
The advent of computer recording has lessened the importance of large state-of-the-art recording facilities. The availability and affordability of professional-quality recording and editing software has led to a legion of home studio recordists with an amazing array of recording tools at their fingertips. Of course, having the tools isn't the same as being able to use them, and audio engineering skills are as valuable as they ever were. It behooves any home studio recordist to work on his or her engineering skills, so that the tools they have are fully utilized.