AKG Acoustics WMS 400 Reflection, Remote Antenna, Room Radius, Sensitivity, Shadow loss, Squelch

AKG WMS GLOSSARY

GLOSSARY

DEFINITIONS FROM A TO Z

This effect, known as “proximity effect”, begins to become audible at a few hundred Hz and at extremely close working distances, the output level may be up to 15 dB higher at 50 Hz than at 1 kHz. This corresponds to about 6 times the normal output voltage.

Reflection

When a signal wave hits an obstacle, it will be reflected, i.e., bounce off the obstacle's surface at an angle equal to the angle of incidence.

Remote Antenna

Antenna that is connected by a special antenna cable to the antenna input socket on a receiver rather than directly to the antenna input socket.

Room Radius

In a room within which a sound is genera- ted, e.g. by a loudspeaker, every point is characterized by its own unique ratio of direct sound and sound reflected from the walls.

The distance from the sound source at which the direct and reflected sound ener- gies are equal is called the “room radius”. Outside the room radius the overall sound pressure level is constant throughout the room in the form of a “diffuse sound field”.

Sensitivity

A microphone's output voltage at any given sound pressure level. A more sensitive microphone will sound louder at the same gain setting (the feedback risk being pro- portionately higher). High sensitivity (con- denser microphones) is needed to drive the mixer adequately when far miking quiet sound sources.

Sensitivity is commonly given in mV/Pa or dBV (referenced to 1 V/Pa) and measured at 1 kHz.

Here are some examples:

D 58		0.7 mV/Pa (-63 dBV)
D 190		1.6 mV/Pa (-56 dBV)
C 1000 S		6.0 mV/Pa (-44 dBV)
C 535		7.0 mV/Pa (-43 dBV)
C 451 EB comb		9.5 mV/Pa (-40.5 dBV)
C 460	Bcomb ULS/61 10.0 mV/Pa (-40 dBV)
C 562	BL	20.0 mV/Pa (-34 dBV)

Shadow loss

Signal loss which occurs in wireless trans- mission if an obstacle blocks the line-of- sight transmission path between transmit- ter and receiver.

Signal Loss

Signal loss in a cable may be due to ohmic resistance, dielectric leakage or radiation loss.

Signal-to-noise (S/N) Ratio

The S/N ratio is the difference between the reference sound pressure level of 94 dB (1 Pa sound pressure) and the equivalent noise level. Contrary to the equivalent noise level, a lower S/N ratio means higher noise and therefore a narrower dynamic range.

Squelch

Electronic circuit that switches the recei- ver off when the received signal is too weak so the associated extraneous noise and the self-noise resulting from the recei- ver being switched off will be inaudible. The squelch threshold is usually user ad- justable within a preset range.

Tone coded squelch, tone code squelch, tone squelch

These terms denote a circuit that will open the audio path only when it detects a system-specific tone within the demodula- ted signal. This tone is higher than 20 kHz, the upper end of the range of human hearing, and is added to the audio signal by the transmitter.

Total Harmonic Distortion (T.H.D.)

A measure of the non-linear distortion of a signal (e.g. a sine wave) that occurs when a microphone or input is overloaded pro- ducing harmonics (overtones) at multiples of the fundamental frequency.

Transient

Temporary change in voltage or current occurring as a voltage or current source is switched on or off, e.g., a transistor con- trolled by a pulse signal.

Transient Response

The ability of a microphone to follow sud- den sound events immediately. Transient response depends on diaphragm mass, transducer damping factor, etc.

Types of Microphones

Microphones utilize different electroacou- stical principles to convert sound energy to electrical energy:

1.Carbon Microphone A microphone using a flexible diaphragm which moves in response to sound waves and applies a varying pressure to a container filled with carbon granules, causing the resist- ance of the microphone to vary corre- spondingly

2.Piezoelectric microphone A microphone in which deformation of a piezoelectric bar by the action of sound waves gen- erates an output voltage between the faces of the bar. Also known as “crystal microphone”.

3.Magnetic microphone A microphone employing a diaphragm acted upon by sound waves and connected to an arma- ture which varies the reluctance in a magnetic field surrounded by a coil. Applications include miniature micro- phones for hearing aids and guitar pickups.

4.Dynamic microphone A conductor (coil attached to diaphragm, ribbon) flexibly suspended in the field of a fixed magnet is vibrated by sound waves. This indu- ces in the conductor an AC voltage that varies in step with the sound waves.

5.Electrostatic microphone A flexible dia- phragm and a fixed electrode together form a two-plate air capacitor whose capacitance varies in step with the sound waves that vibrate the dia- phragm. Also known as “capacitor microphone” or “condenser micro- phone”. In electret microphones one of the electrodes carries a permanent charge.

UHF

Ultra High Frequency

VHF

Very High Frequency

Vibrational Noise

In addition to air-borne sound, micro- phones also pick up mechanical noise such as impact, footfall, handling, or cable noise. Such unwanted noise can be re- duced by special design features (trans- ducer shock mount, compensation systems, bass cut)

Vocal Microphone

A microphone specifically designed for vocal use on stage. It incorporates a pop screen, a transducer shock mount to re- duce handling and impact noise, and is particularly rugged so it will survive the occasional drop from the stand.

Many vocal microphones have an upper midrange (3 to 8 kHz) peak to make the voice cut through. In the studio, vocals are ideally recorded from 30 cm (1 ft.) or even farther, usually with condenser micro- phones.

Wavelength

The distance between two consecutive peaks (or troughs) of a sine wave.

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