Manufacturers' Specifications
Bruel & Kjaer 3361
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 ° downwards 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
| 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 |
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 |
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 Earl 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. |
- Gracey and Associates 01933 624212
- BSI approved for the hire of noise and vibration instruments
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