TECHNOLOGIES

In this section you can learn more about the technologies Sound Temple use. For ease of navigation this guide has been split into multiple pages and you can jump to a topic that interests you by clicking the links below.

• Introduction
• Electronic Signal Generation
• Digital Audio Signal Generation
• Sample Rate
• Bit Depth
• Digital and Analogue Audio Signal Manipulation
• Digital Audio Mastering
• Clip Removal
• Volume Control
• Panning
• Normalisation
• Compression
• Limiting
• Expansion
• Noise Gates

Limiting

Limiting is simply an extreme form of compression where the input/output relationship become very 'flat', i.e. a ratio of 10:1 or higher. This places an extreme limit on the signal level. Limiting can be seen in the above figure 2.4.6.

Expansion

Expansion is the opposite of compression and uses the inverse of the function expressed in 2.4.6. The amount of expansion that is applied is usually expressed as a ratio, such as 2:1, 4:1, etc. This ratio means that while the input is below the threshold, a change in the input level produces a change in the output that is two times, four times, etc. as large. A 4:1 expansion ratio (with the input level below the threshold) and a dip of 3 dB in the input will produce a drop of 12 dB in the output. When an expander is used with extreme settings where the input/output characteristic becomes almost vertical below the threshold i.e., an expansion ratio larger than 10:1, it is often called a noise gate. In this case, the input signal may be very heavily attenuated or removed entirely. This can be envisaged as an on or off switch for an audio signal. When the signal is high enough, the switch is on and input appears at the output, but when it drops below the threshold, the switch is off and there is no output. The key parameter in this case is the threshold.

Noise Gates

The idea of simple gating is simplicity itself. If an input signal falls below a set threshold level, then the output is turned off. Noise gates are commonly used with electrically noisy equipment, such as old analogue synthesisers and guitars. Noise gates are also particularly in vogue with action use being applied to drums. This has the effect of creating a 'punchy' electronic sound.

A noise gate will remove unwanted, background, high frequency noise when an instrument is not sounding. A noise gate is often used for mastering to remove any unwanted, spurious studio noise when a signal falls below a specific volume level. It should be noted that a noise gate might be used as an effect by defining the threshold parameter to be a high value. The result is that only the loud parts of a sound can be heard.