Manufacturers' Specifications
Bruel & Kjaer 3361

B&K 3361 : Speech Transmission Meter consists of two parts, a 4225 Transmitter and a 4419 Receiver :

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B&K 4225 Transmitter - RASTI Test Signal

Noise Source :
Pseudo-random pink noise

Octave Filters :
500 Hz and 2 kHz , in accordance with IEC 225

Modulation Frequencies : - accuracy ± 0.1 Hz

Freq. No.	500 Hz	2 kHz
1	1.02 Hz	0.73 Hz
2	2.03 Hz	1.45 Hz
3	4.07 Hz	2.90 Hz
4	8.41 Hz	5.81 Hz
5		11.63 Hz

Output :
Internal Speaker : Reference output level at 1 m in the reference direction is 59.0 dB in 500 Hz octave and 50.0 dB in the 2 kHz octave, maximum output level +10 dB re. reference level. Reference direction 30 ° down wards marked by an arrow on the cabinet

External Speaker : At max setting, Ref +10 dB a minimum of 4.0 Vp into greater than 4 ohms - 1 Vrms assuming 2 kHz octave is 9 dB below 500 Hz octave

Electrical Output : Symmetrical via 3-pin XLR fixed male connector.
Source Impedance : 2 x 30 ohms
Minimum Output : 0.16 Vrms, 0.08 mV single ended, for max setting, Ref +10 dB.
This simulates the output which would be obtained from a microphone of sensitivity 2.7 mV/Pa placed 1 m from the internal speaker.
Crest Factor : Max 15 dB
Balance Adjustment : For 2 kHz re 500 Hz octave level, -3 to -15 dB

Power Supply :
Batteries : 6 x LR20 alkaline cells
Battery Life : 15 hours

Environmental :
Temperature : 5 °C to 40 °C
Humidity : 0 to 90 %RH, no condensation

Size and Weight :
Height = 138 mm, Width = 251 mm, Depth = 300 mm
Weight = 5 kg, 10 lb

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B&K 4419 Receiver :

Input :
Preamplifier : 5-pole socket for 2642 preamplifier and 4129 microphone.
Direct Input : BNC socket, 25-50 kohms input impedance
Sensitivity : 30 mV produces a 94 dB display
Range : 20 to 121 dB dynamic range for a sinusoidal signal

RASTI Input Range :
500 Hz octave, 29 to 115 dB, for RASTI signal
2 kHz octave, 25 to 115 dB, for RASTI signal
Linearity : ± 0.2 dB for specified sinusoidal input range, excluding effect of internal noise floor
Input Passband : 330 to 3000 Hz,  ± 0.25 dB. Low frequency cut off -3 dB at 230 Hz, 18 dB/octave roll off

Internal Noise Floor :
Max 25 dB for 'cal' mode
Max 18 dB in 500 Hz band
Max 14 dB in 2 kHz band

Detector Crest Factor :
15 dB for max error of 0.1 dB

Calibration :
Adjustable for each input. Nominal frequency 1 kHz

Octave Filters : 500 Hz and 2 kHz, according to IEC 225 Modulation Analysis : Frequencies Analysed

Freq. No.	500 Hz	2 kHz
1	1.02 Hz	0.73 Hz
2	2.03 Hz	1.45 Hz
3	4.07 Hz	2.90 Hz
4	8.41 Hz	5.81 Hz
5		11.63 Hz

Modulation Frequency Accuracy : ± 0.1%
Analysis Method : Discrete Fourier Analysis

Measurement Period	8 s	16 s	32 s
DFT Analysis Time	6.88 s	13.76 s	27.53 s
Window	Hanning	Cosine Tapered
Equivalent. Noise Bandwidth	0.22 Hz	0.09 Hz	0.04 Hz

Measurement Mode	Cal	Single	Run
Display update	1 s	8;16;32 s	8;16;32 s
Frequency Range	300 Hz - 3 kHz	500 Hz - 2 kHz oct	500 Hz - 2 kHz oct

Calibration Averaging Time :
0.5 s

Display :
4-digit, 7-segment LCD

Displayed Measurements :
Speech Transmission Index - RASTI - according to IEC 268

The following measurements are made for 500 Hz and 2 kHz octaves separately :
Speech Transmission Index
Modulation Indices
Octave Sound Pressure Levels
Equivalent Signal to Noise Ration, S/N Equiv.
Equivalent Early Decay Time, EDT Equiv.
Level Difference, 2 kHz re 500 Hz octave

Also displayed are :
Record Number : Special Number for data output : Self Test Number : Error Codes

Self Tests :
A set of 9 self tests which check the front panel, microcomputers and output

Digital Output :
RS-232C : EIA and B&K Serial Interface Standard
Socket : accepts 5-pole plug, JP 0510
Baud Rate : 110 to 19200, factory set to 1200

Environmental :
Temperature : 5 °C to 40 °C
Humidity : 0 to 90 %RH, no condensation

Size and Weight :
Height : 138 mm
Width : 251 mm
Depth : 300 mm
Weight : 5 kg, 10 lb

E&OE - specifications subject to change without notice.

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Gracey & Associates   01933 624212

BSI accreditation for instrument hire and calibration

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B&K Help Line - 01763 255780