AKG Acoustics WMS 400 Electromagnetic Wave Spectrum, Distortion Environment, Directional Antenna

AKG WMS GLOSSARY

GLOSSARY

DEFINITIONS FROM A TO Z

Inside a bass

drum 3 cm 140 dB (one inch)

from the head

130 dB

Tom-toms 3 cm (one in.)

distance; 120 dB 60 watt guitar

amp, at 30 cm

(12 in.) 110 dB distance

Loud vocals, 100 dB at 15 cm

(6 in.) distance

Acoustic 90 dB guitar, chords

strummed with 80 dB plectrum, at

40 cm (16 in.)

70 dB

Acoustic guitar, at

40 cm (16 in.) 60 dB played

“fingerpicking”

50 dB

Noise level in

an average 40 dB city apparment

20 dB

Threshold of hearing 0 dB

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

much less sound energy is absorbed by a	Electromagnetic Wave Spectrum
directional microphone than an omnidirec-	Range of frequencies of electromagnetic
tional microphone.	radiation.
Distortion	Environment
Dynamic microphones virtually never dis-	Dynamic microphones will generally stand
tort the signal. To be precise, their distor-	up to extreme environmental conditions
tions at very high sound pressure levels	such as temperatures from -25 °C to +70 °C
(<130 dB) cannot be measured because	and high humidity.
loudspeakers are incapable of reproducing
such levels distortion free. For this reason,	Condenser microphones, however, are sus-
we state no maximum SPL for dynamic	ceptible to humidity and condensation.
microphones.	When an object is damp and colder than its
However condenser microphones with their	environment, condensation water will form
	on its surface. Drops of condensation water
built-in preamplifier may overload at high	inside the transducer or high-impedance
sound levels. When close miking (from a	preamplifier will cause crackling noises.
few inches) loud instruments such as
drums or trumpets the microphone sensiti-	Storing condenser microphones:
vity should be reduced. With the C 535,
simply use the preattenuation switch.	1. Store the microphone in a dry and warm
Directional Antenna	place. It should never be colder than its
	environment. If it has been transported
Antenna whose sensitivity is highest within	in a cold car or van, allow it to warm up
a limited angle in front of the antenna.	before use.
Directional antennas are used mainly where
standard receiving antennas cannot be	2. The supplied silica gel absorbs humidity.
mounted within the range of the transmit-	It will maintain this property as long as
ters so the transmitter signals must be	you keep it in the sealed package and
picked up from greater distances (e.g., in	may be regenerated in the oven if neces-
open-air arenas).	sary.
Diversity	3. Be sure to protect condenser micropho-
Reception technique that ensures clear	nes from rain when using them outdoors.
reception even in difficult environments.
Diversity receivers use several antennas for	Equivalent Noise Level
the same carrier frequency and some	Since condenser microphones incorporate
models use several receiving sections, too.	a preamplifier, they introduce a low amount
Downtime	of self-noise which appears at the micro-
	phone output as an unwanted signal volta-
Period of time during which a system is	ge. This noise voltage is measured using
inoperative.	standard weighting filters and the result

➂

Dropout	stated as the equivalent noise level in dB.
	An equivalent noise level of 20 dB, for
Momentary loss of signal due to squelch	instance, means that the self-noise of the
operation or interference.	microphone is as loud as a sound at 20 dB
	SPL (see dB SPL).

Crosstalk	Dynamic Microphone
The undesired coupling of signals from one	A coil attached to a diaphragm is driven by	Noise level in quiet recording studio:
channel to another channel.	the sound waves and vibrates between the	A low equivalent noise level means that the
dB SPL	poles of a magnet. This movement induces	microphone's self-noise is low. The self-
	in the coil a voltage which corresponds to	noise voltage is weighted either conforming
Decibel Sound Pressure Level. A measure	the sound pressure. Dynamic microphones	to IEC 268-1 and DIN 45 405 using the
of the sound level referenced to 20 µPa	handle high sound levels without overloa-	filter according to CCIR 468-3 with the
(the sound pressure corresponding to the	ding and are very rugged. They require no	“quasi-peak” value being quoted, or in
threshold of human hearing). A 6-dB	operating voltage. Dynamic microphones	accordance with IEC 651 or DIN 45 412
increase in SPL would sound about twice	from AKG are designated by the letter “N”	using the A-weighting curve with the rms
as loud.	in front of the model number. Also known	value being quoted. Studio engineers seem
Deep Fade	as “moving coil microphone”.	to prefer the CCIR weighting while A-
		weighting is still accepted as well.
Massive decline of received signal strength	Electret Condenser Microphone
due to cancellation of the carrier in multi-	Condenser microphone that needs no pola-	ERP
path transmission situations.	rization voltage. Instead, a special metali-	Equivalent Radiated Power,
Directivity Factor	zed plastic “electret foil”, in which a per-	a measure of a transmitter's RF output.
	manent electrical charge has been stored
The directivity of a microphone can be	by application of heat and a high polarizing	Far-Near Difference
expressed in terms of the amount of sound	voltage, is used either for the diaphragm or	The difference between the shortest and
energy it absorbs out of a diffuse sound	the fixed electrode. The latter type is called	the longest distance between stage and
field. The directivity factor indicates how	“back plate electret microphone”.	antenna.

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