From dB to Dynamic Mic

 

dB
See Decibel

DC
Abbreviation for direct current.

Decibel (dB)
1) Relative measurement for the volume (loudness) of sound. Also used to measure the difference between two voltages, or two currents. See Zero dB.
2) A numerical expression of the relative loudness of a sound. The difference in decibels between two
sounds is ten times the common logarithm of the ratio of their power levels.

Delay
Outboard sound equipment that can momentarily stores a signal being sent to part of a P.A. system so that delayed reinforced sound reaches the audience at the same time as live sound from the stage.

Delay (Digital, Analogue)
1) Effect used to create echo…echo…echo…echo…echo…
2) In more advanced systems used in very large venues, delay can be used to time the arrival of the signal to the speakers in the back of the room so that people in the back hear the sound coming from those speakers at the same time that the sound coming from the speakers in the front of the room arrives.

Diaphragm
A thin flexible membrane or cone that vibrates in response to electrical signals to produce sound waves. Distortion is usually referred to in terms of total harmonic distortion (THD) which is the percentage of unwanted harmonics of the drive signal present with the wanted signal. Generally used to mean any unwanted change introduced by the device under question.

Digital Recording
1) ADAM : (Akai Digital Audio Multitrack). 12 track recording onto Video 8 tape. 16 bit, 44.1 or 48 kHz sampling rate.
2) DAT (Digital Audio Tape) Cassette-like system which has much higher quality than standard audio cassettes. Widely used in gathering sound effects, for news gathering, and for playback of music.
3) DCC (Digital Compact Cassette) Rival to DAT which also plays standard audio cassettes.
4) MiniDisc : Uses computer disk technology, rather than tape. A laser heats an area of magnetic disk which is then written to by a magnetic head. When cooled, the magnetic information is read from the disk by laser. Tracks can be named, and are instant start. Very theatre-friendly system.
5) Direct to Disk : Uses the hard disk present in most PCs as the recording medium.

Diffraction
The breaking up of a sound wave caused by some type of mechanical interference such as a cabinet edge, grill frame, or other similar object.

Direct box
Used in line to convert a high impedance signal into a low impedance signal.

Distorted
The way your PA sounds just before it blows up. Fuzzy and scratchy. If you hear this, it either means you have something hooked up wrong, or something in the system is going bad. It could be anything from your super expensive soundboard to a five dollar patch cord.

Distortion
Usually undesirable result of overloading sound equipment. Reducing the levels can remedy the situation.

Dolby
Trade name for a series of noise reduction systems that have become standard on many tape playback machines. Many film soundtracks are produced using this process. Different varieties are found from Dolby B on most personal cassette players, to Dolby SR and Digital, the current state of the art for cinema.

Driver
See transducer. Dynamic Range – The range between the quietest and the loudest sounds a device can handle (often quoted in dB).

Dry
Describes a sound coming from the PA with no effects on it.

Dynamic Mic
Robust type of microphone which picks up the sound on a diaphragm connected to a coil of wire which moves within a magnet. An alternating current is induced into the wire which provides the electrical output. Most dynamic mics have low output impedance of 200 Ohms. See Condenser Mic.