Sound Recording and Reproduction

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2

The Recording Studio

A recording is made in a recording studio. Studios range from transformed garages or basements to multimillion-dollar facilities with state-of-the-art equipment. Professional recording studios contain two types of rooms: performance spaces and control rooms.

Performance spaces must be acoustically isolated from the rest of the world so that external sounds are not recorded. Many studios also have small booths where individual performers can be separated from one another. Some home studios have no formal performance spaces but have one space that serves both as a control room and as a performance space. MIDI (musical instrument digital interface) studios have no need for performance spaces, as all sounds are electronically generated. It is the size and quality of these performance spaces that has become one of the primary differences between high-quality studios and recordings and low-end studios, which often produce recordings that seem to be missing that little “something.”

The control room contains the mixing console and recording equipment. It is usually located next to the performance space. A window between the two spaces allows eye contact between the engineer and the performers. The mixing console is traditionally the central component where all of the recording devices are interconnected. Depending on the complexity of the recording, these devices might include microphones, signal processors (devices that electronically alter sounds), multitrack recorders, computers, and synchronization devices. Today studios can have a computer monitor as the central fixture, with the computer containing the DAW and the audio interface (AI) being the dominant piece of equipment visible. Sizes and styles of control rooms and their equipment have come to vary widely in type, quality and expense.

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3

Making a Recording

A recording begins with the sound source, usually someone singing or playing an instrument. The performers’ sounds are captured by carefully placed microphones and fed into a mixing console. Electronically produced sounds, such as those from electric guitars or synthesizers, are fed directly into the mixing console or AI (audio interface).

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The mixing console or the DAW serves as the central element of the recording studio. The console routes signals from one location to another around the studio or the DAW will route the signal to various locations in software. This allows the engineer to control the balance and sound qualities of signals, and allows people to monitor the signals in many ways. Separate tracks are often used to layer individual performances of parts into a complete song. During this process, when a sound reaches the mixing console or AI immediately after a performance it is directed to a track on a multitrack tape recorder or a DAW. There the sound from each voice or instrument is placed on its own track, where each individual sound can be accessed again later. Once all of the performances have been assembled on the available tracks, a mix engineer takes over or the same person changes roles.

The sounds from the multitrack tape recorder are then played back through the mixing console. The mix engineer works with the producer to select the materials that will appear in the final version of the recording. The engineer shapes the final sound qualities of the instruments and voices by signal processing and establishes the loudness levels of the instruments in relationship to one another. When this process is completed, the recording exists in its final form.

The mastering engineer is employed to create the final album, which is the mixture of any number of songs and will become the final CD. This person will put the songs in the correct order, will make certain the correct amount of silence separates each song, will adjust the loudness levels of the songs if needed, and might adjust other aspects of sound quality. They are also responsible for ensuring the technical quality of the CD (such as eliminating noises) and for adding all of the industry standard (“Red Book”) coding necessary for the replication process and for the final CD to be playable on a CD player.

Often, recordings are made specifically for radio, movie, or television use. In these cases a record label may not be involved. Production companies (or individuals) copyright the recordings and distribute them directly to the radio, television, or movie producers. Such recordings are usually made in recording studios, but the means by which these recordings are brought to market differ for each project.

III

Sound Reproduction

Sound reproduction systems for home listening combine many different formats and technologies. Compressed audio files (such as MP3 and AAC), compact discs (CDs), records, and tapes are the most common formats for prerecorded sound. Players for each of these formats vary in size, quality, and price. Portable systems often combine different playback devices for maximum convenience, whereas traditional home systems generally connect separate components together. Portable systems such as the iPod nano can be as small as the size of a package of chewing gum. This gives the home listener more choice and flexibility when choosing or upgrading components.

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Amplifiers and Loudspeakers

The electronic energy coming from a playback unit must be brought up to an adequate level before it can be heard. A preamplifier takes signals from any number of different sources and brings them all to the same level. A preamplifier has inputs for a cassette tape deck, a CD player, a radio (known as a tuner), a turntable, a video cassette recorder (VCR), MP3 player, DVD player, and other devices, such as a second tape deck. The user may choose which device’s input signals the unit will respond to, selecting which signal is delivered to the preamplifier's output.

The output of the preamplifier is fed to the input of a power amplifier. This device takes the electronic energy from the preamplifier and increases the voltage or power of the energy, so the amplifier can deliver enough power at its output to drive loudspeakers.

The output of the preamplifier is fed to the input of a power amplifier. This device takes the electronic energy from the preamplifier and increases the voltage or power of the energy, so the amplifier can deliver enough power at its output to drive loudspeakers.

An integrated amplifier contains both a preamplifier and an amplifier within one device. An integrated amplifier that also contains an AM/FM radio tuner is known as a receiver. A receiver is the most common form of amplifier. Separate components (an amplifier, a preamplifier, and a tuner) are usually found in more expensive audio systems. It is common for receivers to be equipped for surround sound input from a DVD player and output to six loudspeakers.

Loudspeakers generally used in home systems come in pairs (or five plus one for surround sound) and resemble boxes. Within each box, or enclosure, there may be one or more actual speakers. The enclosure itself affects the loudspeaker’s performance. The speakers within the enclosure share the same signal. The largest speaker handles the lowest frequencies, and the smallest speaker handles the highest. The signal from the amplifier is divided up into frequency ranges and then is routed to the specific speakers. These speakers work as a single unit, reproducing the recording in the most accurate way.

Placing loudspeakers in a corner or too near a wall will change their sound quality and efficiency. Some frequencies will be emphasized and others diminished, changing their frequency response. The stereo imaging will be distorted when some frequencies radiate off walls that are too close. A small air space between a speaker cabinet and a wall can also cause acoustic dampening at some frequencies. Users should follow manufacturer recommendations and the rule of keeping loudspeakers three feet away from any surface (wall, floor or ceiling).

Surround system calibration is critical for accurate listening to surround recordings. The loudness level (as sound pressure level) should be the same for all five loudspeakers when measured from the optimal listening location that is equidistant from all five loudspeakers. The tuner should allow for all speakers to be adjusted equally at one time, and for the system to be calibrated by setting the loudness and equalization of each channel separately.

Headphones are actually two small loudspeakers connected by a band and designed to be placed over the listener's ears. Headphones are an important part of a portable stereo system. Early headphones were heavy and bulky, but modern headphones are light and small, with improved sound quality. Earbuds have continued the trend in diminishing size. While they will not replace loudspeakers for quality of listening experience, headphones create a private listening experience and ease of “on the go” listening.

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Playback Devices

Different types of media, such as CDs, DVDs, records, and tapes, require different devices to recall and play recorded sounds. Home theater systems are used with television sets to simulate the experience of watching a movie in a theater.