B&K 2250 FFT and Tonal Assessment Options - BZ 7230 and BZ 7231
The B&K 2250 is a multi-function meter, for other options and accessories click a link
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B&K 2250 - Home Page B&K 2250 - Summary Table B&K 2250 - Specifications Options and software included BZ 5503 - PC - Utility Software BZ 7222 - Sound Analysis Software BZ 7223 - Frequency Analysis Software BZ 7224 - Logging Software BZ 7226 - Sound Recording Software |
Other options available BZ 7225 - Enhanced Logging Software BZ 7227 - Reverberation Time Software BZ 7228 - Sound Insulation Software BZ 7230 - FFT Measurement Software - this page BZ 7231 - Tonal Assessment Software - this page |
| Accessories etc., Environmental and Factory Noise Kits and other popular accessories |
| B&K 2250 with BZ 7230 FFT - Fast Fourier Transfer Software | £ 31 a day * |
| B&K 2250 with BZ 7230 FFT Software + the BZ 7231 Tonal Assessment Software | £ 35 a day * |
On this page we describe the main features of the BZ 7230 FFT, narrow band, software option and the BZ 7231 Tone Assessment option.
Frequency analysis based on the Fast Fourier Transform (FFT) algorithm is the tool of choice for measurement and analysis of machinery noise and vibration. The frequency profile of a machine is its fingerprint, revealing the sources of noise and vibration and their paths to the measurement position.
The 2250 meter with FFT Analysis Software enables high frequency resolution up to 6400 lines of analysis over a wide dynamic range and the touch screen allows you to zoom into measurements, choose different cursors and adjust the scaling.Select the FFT option and you are ready to perform FFT measurements using the 2250's precision microphone. For vibration measurements, add an accelerometer. A Vibration Calibrator is also recommended.
Include the Tone Assessment option to evaluate 'tonal' components in accordance with ISO 1996-2 (2007) Annex C.
Uses
FFT analysis of sound or vibration
Features
Tonal Assessment Features
The BZ 7230 FFT Analysis Software is an application 'module' for the 2250 hand-held meter. The Fast Fourier Transform is a digital signal processing technique that converts a time record into a narrow band constant bandwidth filtered spectrum. Measurements are defined by specifying the frequency span and a number of lines (or filters).
FFT sound and vibration analysis is all about the details and the zoom facility allows you to focus on any part of the frequency range by specifying the centre frequency for the analysis span, resolutions down to 1/64 Hz are possible see the table for details.
| Frequency Span | 100 | 200 | 500 | 1000 | 2000 | 5000 | 10000 | 20000 |
| 100 lines | 1 | 2 | 5.5 | 10 | 20 | 50 | 100 | 200 |
| 200 lines | 0.5 | 1 | 2.5 | 5 | 10 | 25 | 50 | 100 |
| 400 lines | 0.25 | 0.5 | 1.25 | 2.5 | 5 | 12.5 | 25 | 50 |
| 800 lines | 0.125 | 0.25 | 0.625 | 1.25 | 2.5 | 6.25 | 12.5 | 25 |
| 1600 lines | 0.0625 | 0.125 | 0.3125 | 0.625 | 1.25 | 3.125 | 6.25 | 12.5 |
| 3200 lines | 0.03125 | 0.0625 | 0.15625 | 0.3125 | 0.625 | 1.5625 | 3.125 | 6.25 |
| 6400 lines | 0.015625 | 0.03125 | 0.078125 | 0.15625 | 0.3125 | 0.78125 | 1.5625 | 3.125 |
Click here to see the B&K 2250 FFT - Fast Fourier Transform Specifications.
Tone Assessment Option BZ 7231.
Noise can be described as tonal if it contains a noticeable or discrete, continuous note. This may include noises such as hums, hiss, screeches, drones, etc., and any such subjective description is open to discussion and contradiction when reported. ISO 1996-2 (2007) Annex C, "Objective method for assessing the audibility of tones in noise reference method", provides measurement procedures to be used to verify the audibility of tones and to quantify them. Although the methodology of any standard could be the subject of much discussion, the result of a test carried out in accordance with it, is not.
Automatically Configured for ISO 1996 Assessments
By its nature, making objective measurements to what is inherently a subjective response to a sound is difficult. Issues such as prominence, amplitude/frequency masking, and calculation of any tonal penalties makes the ISO 1996 assessments more than a simple FFT measurement.
BZ-7231 Tone Assessment Option for Type 2270 and 2250 Hand-held Analyzers running FFT Analysis Software BZ-7230, offers a quick and easy `in-the-field' objective assessment of tonal noise components, in compliance with ISO 1996 assessments. The facility to carry out the ISO Standard tone assessment on the analyzer with an immediate result offers objective feedback about whether you have `found the problem' or need to take further measurements.
In addition, the analyzer offers an easy way of setting up the FFT analysis to follow the ISO 1996-2 standard. When this option is selected, the analyzer automatically selects the appropriate measurement configuration. Simply press `start' and the measurement and analysis are in progress.
All the Details Available Instantly
On completion of the measurement, the calculation of tonal parameters for all the possible tonal candidates in the analysis takes only a few seconds, after which the following comprehensive list of results can be displayed on the spot:
Kt the value added to the LAeq to give the tone-corrected rating level
Lta the audibility of all tones found in the same critical band as the selected tone
Lpn the Total level of the masking noise in the band containing the selected tone
Lpti the Level of the selected tone
Lpt the total Level of all tones in the critical band containing the prominent tone
Critical Band - the start and end of the critical band containing the selected tone
The LAeq and other broadband parameters are measured simultaneously by the hand-held analyzer and the tone corrected rating level can be calculated on the spot as shown in the typical FFT spectrum display above.
Click here to see the B&K 2250 Tonal Assessment Specifications.
* Our standard hire charges are based on a 4-day minimum period, details other options.
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