Preliminary Technical Data

WM7121

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PTD, Rev 2.0, October 2012

5

ACOUSTIC AND ELECTRICAL CHARACTERISTICS

PARAMETER

SYMBOL

TEST CONDITIONS

MIN

TYP

MAX

UNIT

Directivity

Omni-directional

Sensitivity (WM7121)

S

94dB SPL

-41

-38

-35

dBV

Sensitivity (WM7121E)

S

94dB SPL

-39

-38

-37

dBV

Acoustic Overload

No Load

THD < 10%

126

dB SPL

Signal to Noise Ratio

SNR

A-Weighted

65

dB

Total Harmonic Distortion

THD

104dB SPL

0.25

%

Dynamic Range

DR

A-Weighted,

Noise floor to 1% THD

91

dB

Frequency Response

-3dB Low Frequency

+3dB High Frequency

62

15000

Hz

Hz

Acoustic Noise Floor

A-Weighted

29

dB SPL

Electrical Noise Floor

A-Weighted

-103

dBV

Power Supply Rejection Ratio

PSRR

100mV RMS, 217Hz

53

dB

Current Consumption

200

µA

Output DC Impedance

100

Ω

TERMINOLOGY

1.

Sensitivity (dBV) – Sensitivity is a measure of the microphone output response to the acoustic pressure of a 1kHz

94dB SPL (1Pa RMS) sine wave.

2.

Signal-to-Noise Ratio (dB) – SNR is a measure of the difference in level between the output response of a 1kHz 94dB

SPL sine wave and the idle noise output.

3.

Total Harmonic Distortion (dB) – THD is the ratio of the RMS sum of the harmonic distortion products in the specified

bandwidth (see note below) relative to the amplitude of the fundamental (ie. Test frequency) output.

4.

Dynamic Range (dB) – DR is the ratio of the 1% THD microphone output level (in response to a sine wave input) and

the idle noise output level.

5.

All performance measurements are carried out with 20 kHz low pass ‘brick wall’ filter and, where noted, an A-weighted

filter. Failure to use these filters will result in higher THD and lower SNR values than are found in the Acoustic and

Electrical Characteristics. The low pass filter removes out of band noise.