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Sound and Vibration Instrument Hire and Calibration

Bruel & Kjaer 3361 Specifications


 
Bruel & Kjaer 3361 RASTI - Speech Transmission Index Meter
 
B&K 3361 : Speech Transmission Index Meter - RASTI Meter £ 24 a day *
 

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


 

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
 


 

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.