Audio Visual Engineering Terms & Definitions

Glossary of Audio-Visual terms, technologies, and abbreviations. Here you will find definitions for common audiovisual terminology.

What is Absorption?

If you struggle trying to keep up with or understand some AV terms, here you will find the definition for common audiovisual terminology. This is a helpful glossary of audiovisual terms.

Absorption is the passing of a substance or force into the body of another substance. For example: When a designer tries to darken a

room, they do not use light-colored materials; they use dark materials. That is because dark colors absorb light, close to black in value. In other words, the eye black absorbs the sunlight, reducing reflections to what we see.

What is Amplitude?

Amplitude is the magnitude of a signal. As represented on a sine wave is the intensity of a wave.

What is an Audio Signal?

An audio signal is an electrical representation of a sound. The following is a typical audio signal chain:

• The sound source creates sound wave vibrations in the air.
• The microphone detects these sound waves’ vibrations.
• The microphone converts vibrations into an electrical signal and processes it.
• The electrical signal ends up in an output device, such as an earphone or loudspeaker. 
• The output device converts the electrical signal back into sound waves.

What is an Audio Processor?

An audio processor allows for delaying the sound arrival from each speaker. It prevents over-modulation or minimizes it when it occurs. Primary functions of audio processors include splitting a full-frequency input into band-limited signals for bi- or tri-amplified systems. Provide equalization to correct the acoustic characteristics of speakers or cabinets. It also detects and prevents overload conditions. 

In audio recordings, audio processing enhances certain features and suppresses others. You can use as many audio processors as you need. Some processors include compressors, limiters, gates, expanders, and filters. 

What are Audio Distribution Amplifiers?

A distribution amplifier is an amplifier that accepts a signal at its input and distributes the signal to two or more outputs. Depending on the type and circuitry, outputs are isolated from each other to a greater or lesser degree. A distribution amplifier comes in handy when you need to take an audio signal and send it to two or more places.

What is a Simultaneous Interpretation System?

Simultaneous Interpretation (SI) systems involve the immediate translation of one language to another. These systems involve at least two professional translators and some electronic equipment for each language. The speaker or presenter using the primary language speaks into a microphone. That transmits sound to a translator in a soundproof booth, wearing a pair of headphones. The translated sound goes to audience listeners wearing headphones through wires or infrared signals.

What is Noise Masking System?

The purpose of noise masking systems is to mask the noise. In a quiet non-reverberant office space, sometimes people unintentionally overhear conversations. Invading privacy and mechanical noises can become disruptive to the work effort. When properly set up, the noise masking system makes these noises less noticeable. That can increase the efficiency of the workforce as well as privacy.

Direct sound, so important for speech intelligibility in paging or reinforcement systems, is undesirable in masking systems. Loudspeakers are throughout the area. They are sometimes oriented horizontally to improve the dispersion and avoid spatial concentration of volume. If used properly, employees will not notice the installation at all. The disruptive noises are less noticeable.

What is Audio Signal Distortion?

In any part of a system (amplifier, equalizer, cable, etc.), there is an ideal, expected output signal waveform. Any false reproduction of audio is a signal distortion. The most common example of distortion occurs in analog equipment. That is when the signal exceeds the capabilities of the equipment receiving or delivering. The better quality of the device. The more accurately it will handle the signal (less distortion).

The resulting signal is squared off if the original signal is beyond the threshold. If the signal amplitude is too low or too high for the device, it may be less intelligible because of signal distortion. The distorted sound is the odd harmonics of the signal amplified and then added back into it.

Manufacturers specify that their product is within a certain allowable tolerance of total harmonic distortion (THD). THD is a small percentage of the signal measured at the maximum specified output of the device.

What is an Audio Compressor?

Audio compressors control the overall amplitude of a signal. That is, by reducing that part of the signal which exceeds an adjustable level; threshold; set by the user. When the signal exceeds the threshold level, a ratio reduces the overall amplitude, adjustable by the user.

For example, if the ratio compression is 2:1 any part of the signal exceeding the threshold level is reduced by one-half.

An audio compressor is a sound processing tool designed to reduce the dynamic range of the input audio signal. It functions by “turning down” loud audio signals and “turning up” softer audio signals. Its purpose is to smooth the audio signal by eliminating or limiting peaks in the audio response. Because compression onset can be variable, it can also modify the attack and decay characteristics of the audio signal. Compressors are available in a stomp box, studio rack format, or software plug-in. Audio compressors increase the apparent sustain of stringed instruments such as guitar and bass by bringing up the level of the device as the note decays (gets softer). Unfortunately, this also increases the noise floor, since a compressor does not differentiate between noise and audio signal.

What is Multicasting?

Multicasting is the ability to transmit a single stream to multiple subscribers at the same time. Unlike conventional streaming, it does not need one stream per recipient. Instead, there is a stream on any segment of the network on which there is a subscriber.

Multicasting allows broadcast stations to offer several channels of digital programming at the same time. For example, a local TV station elects to send out three DTV programs. The first program transmits HDTV shows and sports, while the second offers SD versions of the same programming.

Finally, a third program carries continuous local weather information. Your digital TV set-top receiver or integrated TV will automatically find all these programs for you and identify each with a unique channel number.

In this case, the first program (HDTV) would appear as channel 6-1. The second program would come up as channel 6-2, and the 24/7 weather programming would show up as 6-3. The digital TV or external set-top receiver knows how many of these TV programs are on each channel by reading the digital program data packets. For example, think of a TV channel as a “digital shoebox.”

What is Audio Video Systems Design and Integration?

The purpose of the Audio Video Systems design and integration is to meet an application’s objective. A well-designed system dictates how efficiently and effectively this performs. You can notice the benefits of an audiovisual system when the whole application is part of an integral system that may include different devices such as LCD, plasma, projector, speakers, remotes, etc. An audio-video system is a tool used by an organization to meet its goals. It should complement its users, its environment, and its application.

What is Feedback?

Feedback is the “squealing” or “howling” generated between microphones and loudspeakers. The feedback occurs if a microphone is near the front of a loudspeaker. 

One way to avoid feedback is through a proper microphone and loudspeaker placement. The best strategy is to place microphones near the sound but behind and far away from the loudspeakers.

What is Frequency?

Frequency is the number of cycles in a given period. Frequency and wavelength are inversely related. While wavelength increases, the frequency decreases. Hertz represents a frequency. 1Hz = one cycle per second. The hertz measurement, abbreviated Hz, is the number of waves that pass by per second. For example, an “A” note on a violin string vibrates at about 440 Hz (440 vibrations per second).

What is Refraction?

Refraction is the bending or changing in the direction of a light ray when passing through a material. The Refractive index is how much light refracts, meaning how great the angle of refraction is. 

What is Dispersion?

Dispersion is the breaking up or scattering of something. In audiovisual, white light has many frequencies and wavelengths. Frequency and wavelength relate to the color of light. The refractive index varies for each of the different wavelengths of light. This difference produces an effect called dispersion.

What is Reflection?

Materials with a mirrored or glossy surface reflect light – changing its direction. The angle at which the original light (incident light) hits the reflective surface predicts the direction of the reflected light.

What is Color?

Color is the byproduct of the spectrum of light. The human eye receives color; while the human brain processes it. When light hits an object, some wavelengths are absorbed while others are reflected. The reflected wavelengths are what we perceive as the object’s color.

What is a Lumen?

A lumen measures the quantity of light emitted from a constant light source across one square meter. Its symbol is lm. Lumens describe how much light contains an area. The lumen is part of a group of standard measurements known as the photometry group, which measures different aspects of light.

What is resolution?

Resolution is the number of pixels used to draw an image on the screen. The total of pixels in a row, multiplied by the number of pixels in a column, indicates the monitor resolution.

For example: in a monitor, if there were 800 pixels across and 600 pixels down the side; then, the resolution would be 800×600. Multiplying 800 times 600 will get the number of pixels used to draw the image (480,000 pixels in this example).

A monitor has to be compatible with the video card in the system. The monitor has to be capable of displaying the resolutions and colors that the adapter can produce. It works the other way around too. If a monitor has a resolution of 1280×1,024 and the adapter has 800×600; then, you will only get 800×600.