Music Glossary - D

De-esser
An audio signal processing device that is used to remove excessive sibilance (The hissy 's' sound heard on some vocal or speech recordings). Often this is a psecial form of compressor that uses an Equaliser as part of the detection circuit.

deciBel (dB)
This is the ratio of two signal levels where the relationship is governed by the equation:

dB = 20Log10(v1/v2)

dBu means that the ratio is measured relative to 0.775V RMS.

dBm means that the ratio is a measure of power. 0 dBm equals 1 milliwatt, or 0.775V across a 600 Ohm impedance.

dBV means that the ratio is a measure of voltage. 0 dBV equals 1 volt.

dB SPL means that the ratio is a measure of Sound Pressure Level. 0 dB SPL equals 0.0002 dynes/ square centimeter, or 20 micro-Pascals.

Demo
This is a trial recording of a song or album. Such recordings are done as promotional recording to obtain work or a Music contract.

Digital Audio Tape (DAT)
This is a cassette-tape storage medium capable of storing digital audio information.

Digital To Analog Converter (DAC)
This is an electronic device that is used to convert digital audio signals into analog audio signals, or more generally to convert digital signals into analog signals.

Direct Current (DC)
This is an electrical signal whose polarity is fixed and whose amplitude remains constant with respect to time.

Direct Injection (DI) Box
This is a box that allows the direct connection of an electrical Musical instrument to the input of a Mixing Desk, as opposed to amplifying the instrument and recording the output with a Microphone.

Direct Output
This is a post-fade output from a Mixing Desk input channel. Direct Outs are commonly used for sending the signal to individual tape tracks during recording.

Distortion
Unwanted change in an audio signal that results in the presence of frequencies in the outpu signal that were not present in the original signal. There are sseveral types of distortion.

Drum Head
Material used to cover the shell of a drum. If struck with a stick or mallet this material will create a tone. Can be made from a number of natural or synthetic fiberous materials.

Drum Key
Tool used in the tuning of a drum. The key is commonly a "T" shape and fits over the top of a lug that runs through the top or bottom rim of a drum shell. By tighting the lug on a drum head the pitch can be raised or lowered.

Drum Stick
Object used to strike a drum. Usually made of wood or synthetic material. Most will have a wooden or nylon tip.

Dynamic Microphone
This kind of Microphone converts acoustic energy to electrical energy by using a moving coil and a permanent magnet. This kind of microphone does not require any external power to be applied.