AKG MP 40 User Manual download pdf (Page 89)

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DEFINITIONS FROM A TO Z

GLOSSARY

Crosstalk

The undesired coupling of signals from one

channel to another channel.

dB SPL

Decibel Sound Pressure Level. A measure

of the sound level referenced to 20 µPa

(the sound pressure corresponding to the

threshold of human hearing). A 6-dB

increase in SPL would sound about twice

as loud.

Deep Fade

Massive decline of received signal strength

due to cancellation of the carrier in multi-

path transmission situations.

Directivity Factor

The directivity of a microphone can be

expressed in terms of the amount of sound

energy it absorbs out of a diffuse sound

field. The directivity factor indicates how

much less sound energy is absorbed by a

directional microphone than an omnidirec-

tional microphone.

Distortion

Dynamic microphones virtually never dis-

tort the signal. To be precise, their distor-

tions at very high sound pressure levels

(<130 dB) cannot be measured because

loudspeakers are incapable of reproducing

such levels distortion free. For this reason,

we state no maximum SPL for dynamic

microphones.

However condenser microphones with their

built-in preamplifier may overload at high

sound levels. When close miking (from a

few inches) loud instruments such as

drums or trumpets the microphone sensiti-

vity should be reduced. With the C 535,

simply use the preattenuation switch.

Directional Antenna

Antenna whose sensitivity is highest within

a limited angle in front of the antenna.

Directional antennas are used mainly where

standard receiving antennas cannot be

mounted within the range of the transmit-

ters so the transmitter signals must be

picked up from greater distances (e.g., in

open-air arenas).

Diversity

Reception technique that ensures clear

reception even in difficult environments.

Diversity receivers use several antennas for

the same carrier frequency and some

models use several receiving sections, too.

Downtime

Period of time during which a system is

inoperative.

Dropout

Momentary loss of signal due to squelch

operation or interference.

Dynamic Microphone

A coil attached to a diaphragm is driven by

the sound waves and vibrates between the

poles of a magnet. This movement induces

in the coil a voltage which corresponds to

the sound pressure. Dynamic microphones

handle high sound levels without overloa-

ding and are very rugged. They require no

operating voltage. Dynamic microphones

from AKG are designated by the letter “N”

in front of the model number. Also known

as “moving coil microphone”.

Electret Condenser Microphone

Condenser microphone that needs no pola-

rization voltage. Instead, a special metali-

zed plastic “electret foil”, in which a per-

manent electrical charge has been stored

by application of heat and a high polarizing

voltage, is used either for the diaphragm or

the fixed electrode. The latter type is called

“back plate electret microphone”.

Electromagnetic Wave Spectrum

Range of frequencies of electromagnetic

radiation.

Environment

Dynamic microphones will generally stand

up to extreme environmental conditions

such as temperatures from -25 °C to +70 °C

and high humidity.

Condenser microphones, however, are sus-

ceptible to humidity and condensation.

When an object is damp and colder than its

environment, condensation water will form

on its surface. Drops of condensation water

inside the transducer or high-impedance

preamplifier will cause crackling noises.

Storing condenser microphones:

1. Store the microphone in a dry and warm

place. It should never be colder than its

environment. If it has been transported

in a cold car or van, allow it to warm up

before use.

2. The supplied silica gel absorbs humidity.

It will maintain this property as long as

you keep it in the sealed package and

may be regenerated in the oven if neces-

sary.

3. Be sure to protect condenser micropho-

nes from rain when using them outdoors.

Equivalent Noise Level

Since condenser microphones incorporate

a preamplifier, they introduce a low amount

of self-noise which appears at the micro-

phone output as an unwanted signal volta-

ge. This noise voltage is measured using

standard weighting filters and the result

stated as the equivalent noise level in dB.

An equivalent noise level of 20 dB, for

instance, means that the self-noise of the

microphone is as loud as a sound at 20 dB

SPL (see dB SPL).

Noise level in quiet recording studio:

A low equivalent noise level means that the

microphone's self-noise is low. The self-

noise voltage is weighted either conforming

to IEC 268-1 and DIN 45 405 using the

filter according to CCIR 468-3 with the

“quasi-peak” value being quoted, or in

accordance with IEC 651 or DIN 45 412

using the A-weighting curve with the rms

value being quoted. Studio engineers seem

to prefer the CCIR weighting while A-

weighting is still accepted as well.

ERP

Equivalent Radiated Power,

a measure of a transmitter's RF output.

Far-Near Difference

The difference between the shortest and

the longest distance between stage and

antenna.

Inside a bass

drum 3 cm

(one inch)

from the head

Tom-toms

3 cm (one in.)

distance;

60 watt guitar

amp, at 30 cm

(12 in.)

distance

Loud vocals,

at 15 cm

(6 in.) distance

Acoustic

guitar,

chords

strummed with

plectrum, at

40 cm (16 in.)

Acoustic

guitar, at

40 cm (16 in.)

played

“fingerpicking”

Noise level in

an average

city apparment

Threshold of

hearing

Loud vocals,

measured in

front of the

mouth;

threshold of

pain

Congas, 2 cm

(one in.) from

the head

Cowbell at

10 cm (4 in.)

distance

Saxophone,

trombone,

played p,

at 40 cm

(16 in.)

distance

Piano, played

pp, at 1 m

(3 ft.) distance

Whispering at

distance of

10 cm (4 in.)

quiet conver-

sation at 1 m

(3 ft.) distance

Noise level in a

good sound-

isolated studio

140 dB

130 dB

120 dB

110 dB

100 dB

90 dB

80 dB

70 dB

60 dB

50 dB

40 dB

20 dB

0 dB

➂

AKG WMS GLOSSARY

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