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Sound and Vibration Instrument Hire and Calibration

B&K 2250 BZ 7227 Reverberation Time Specifications

To see the specifications for the various options available, click a link

Bruel & Kjaer Sound Level Meter
BZ 7222 : Sound Analysis Software
BZ 7223 : Frequency Analysis Software
BZ 7224 : Logging Software
BZ 7225 : Enhanced Logging Option
BZ 7226 : Sound Recording Software
BZ 7227 : Reverberation Time Option
BZ 7228 : Sound Insulation Option
BZ 7230 : FFT Analysis Option
BZ 7231 : Tone Assessment Option
B&K 2250 : Home Page
B&K 2250 : Specifications
B&K 2250 : Detailed Image
Bruel & Kjaer 2250 + Reverberation Time Software - BZ 7227 £ 36 a day *

Correction Filters

For Microphone Types 4189, 4191, 4193, 4950 and 4952, BZ-7227 is able to correct the frequency response to compensate for sound field and accessories

Broadband Measurements

A and C-weighted broadband detectors with F exponential time weighting
Overload Detector: Monitors the overload outputs of all the frequency weighted channels


LAF and LCF for Display as Numbers or Quasi-analogue Bars

Measuring Ranges

When using Microphone Type 4189:
Dynamic Range: From typical noise floor to max. level for a 1 kHz pure tone signal, A-weighted: 16.6 to 140 dB
Primary Indicator Range: In accordance with IEC60651, A-weighted: 23.5 dB to 123 dB
Linear Operating Range: In accordance with IEC61672, A-weighted: 1 kHz: 24.8 dB to 140 dB

Frequency Analysis

Centre Frequencies
1/1-octave Band Centre Frequencies: 63Hz to 8 kHz
1/3-octave Band Centre Frequencies: 50Hz to 10 kHz


LZF spectrum for display only
LZeq spectra sampled at 5ms intervals

Measuring Ranges

When using Microphone Type 4189: Dynamic Range: From typical noise floor to max. level for a pure tone signal at 1 kHz 1/3-octave: 1.7 to 140 dB
Linear Operating Range: In accordance with IEC61260: < 20.5 dB to 140 dB

Internal Generator

Built-in pseudo-random noise generator
Spectrum: Selectable between Pink and White
Crest Factor:
Pink Noise: 4.4 (13 dB)
White Noise: 3.6 (11 dB)
Bandwidth: Follows measurement frequency range
Lower Limit: 50 Hz (1/3-oct.) or 63 Hz (oct.)
Upper Limit: 10 kHz (1/3-oct.) or 8 kHz (oct.)
Output Level: Independent of bandwidth
Max: 1 Vrms (0 dB)
Gain Adjustment: -60 to 0 dB
When bandwidth is changed, the level for all bands is automatically adjusted to comply with the set output level.
Correction Filters: for sound sources Type 4294, Type 4295 and Type 4296: Flat or Optimum.
Turn-on and Turn-off Time: Equivalent to RT = 70 ms
Repetition Period: 175 s
Output Connector: Output Socket
Control: See Measurement Control

External Generator

Selectable as alternative to Internal Generator For controlling external noise generator
Levels: 0V (Generator off), 4.5V (Generator on)
Rise-time and Fall-time: 10 µs
Control: See Measurement Control

Reverberation Time

EDT, T20 and T30 in octave or 1/3-octave bands
Decays: Measured and stored using averaging time of 5 ms
Evaluation Range: -5 to -15 dB for EDT, -5 to -25 dB for T20 and -5 to -35 dB for T30
Measurement Time: Automatic selection of measurement time for the decays based on the actual reverberation time of the room
Maximum Measurement Time: from 2 to 20 s
Averaging: EDT, T20 and T30 measurements can be averaged (arithmetic averaging or ensemble averaging)
EDT, T20 and T30 Calculation: From slope in evaluation range
Slope Estimation: Least squares approximation
Quality Indicators: Quality Indicators with status information like Overload, Curvature in %, etc., extensive list of Status information
Quality Indicators are available on reverberation time spectra for each frequency band, and as overall quality indicators for each measurement position and for the total project (room)
Reverberation Time Range: Max. 20 s, min. 0.1 - 0.7 s, depending on bandwidth and centre frequency
Wide Band Reverberation Time: The arithmetic average of the Reverberation Time within a selectable frequency range is calculated

Measurement Displays


Overview Map

Map of Source and Receiver positions with reverberation time readout for a selectable frequency band on each measurement position together with quality indicator.
Organisation of Source and Receiver Positions: measure at all receiver positions for each source or measure in a number of positions (1 to 10) for each source
Source and Receiver positions can be added, moved or deleted

Overview Table

Table of measurement positions with reverberation time readout for selectable frequency band on each position together with quality indicator. Positions can be included/excluded from Room average

Sound Level Spectrum

LZF spectrum plus A and C broadband bars
Y-axis: Range: 5, 10, 20, 40, 60, 80, 100, 120, 140 or 160 dB. Auto zoom or auto scale available
Cursor: Readout of selected band
Quality indicator for each frequency band

Reverberation Time Spectrum

One or two spectra can be displayed
Y-axis: Range: 0.5, 1, 2, 5, 10 or 20 s. Auto zoom available
Cursor: Readout of selected band
Quality Indicator for each frequency band

Reverberation Time Spectrum Table

One or two spectra can be displayed in tabular form


Decay curve for a position or the room average available for each frequency band
Display of evaluation range and regression line
Readout of Curvature in %
Y-axis: Range: 5, 10, 20, 40, 60, 80, 100, 12 or 160 dB. Auto zoom or auto scale available

Measurement Control

Measurement Sequence: Supports measuring:
at all receiver positions before using another source
at a receiver position for all sources before measuring at a new position
at subsequent receiver positions without source information, or
at manually selected source and receiver positions
During measurement, the instantaneous sound level spectrum is displayed. After measurement, the reverberation time is displayed
Interrupted Noise Excitation: Measurements are started manually and can be automatically stored on completion of measurement.
The noise generator is turned on and off automatically
Escape Time: 0 to 60 s
Build-up Time: 1 to 10 s
Number of Decays per Measurement: 1 to 100, ensemble averaged into one decay
The generator can be turned on and off manually for checking equipment and sound levels
Impulse Excitation: Manual start of first measurement. When level (say from starter pistol) exceeds the user-selected trigger level, the decay is recorded and backwards integration performed
Schroeder Method. The trigger can then be armed automatically for measuring at the next position
Sound Recording: Recording of the Z-weighted measured signal can be done at each position
Sound Recording requires a CF or SD-Card for data storage

Measurement Status

On Screen: Information such as overload, awaiting trigger and running/paused are displayed on screen as icons
Traffic Light: Red, yellow and green LEDs show measurement status and instantaneous overload as follows:
Yellow LED flashing every 5 s = stopped, ready to measure
Green LED flashing slowly = awaiting trigger or calibration signal
Green LED on constantly = measuring
Yellow LED flashing slowly = paused, measurement not stored
Red LED flashing quickly = intermittent overload, calibration failed


Initial calibration is stored for comparison with later calibrations
Acoustic: Using Sound Calibrator Type 4231 or custom calibrator. The calibration process automatically detects the calibration level when Sound Calibrator Type 4231 is used
Electrical: Uses internally generated electrical signal combined with a typed-in value of microphone sensitivity
Calibration History: Up to 20 of the last calibrations made are listed and can be viewed on the instrument

Signal Monitoring

Input signal A, C or Z-weighted can be monitored using an earphone/headphones connected to the headphone socket
Headphone Signal: Input signal can be monitored using this socket with headphones/earphones
Gain Adjustment: -60 dB to 60 dB

Voice Annotations

Voice annotations can be attached to the Reverberation Time Project, to Sources, to Receivers and to measurements at each Position
Playback: Playback of voice annotations or sound recordings can be listened to using earphone/headphones connected to the headphone socket
Gain Adjustment: -60 dB to 0 dB

Data Management

Project Template: Defines the display and measurement setups
Project: Measurement data for all positions defined in a room are stored with the Project Template
Job: Projects are organised in Jobs Explorer facilities for easy management of data (copy, cut, paste, delete, rename, view data, open project, create job, set default project name)
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E&OE - specifications subject to change without notice.