DS-2000 Frequently Asked Questions
Question number FAQ-0686
A simple method for determining the sound power level using data from the DS-0225 three-dimensional sound intensity software is as follows:
This section explains a simplified method for calculating the acoustic power level using DS-0225 three-dimensional acoustic intensity data. It is assumed that trace data for one side of the sound source has already been created using the DS-0225 acoustic intensity analysis software. While the calculation should ideally cover the entire area surrounding the sound source, this section focuses on explaining the calculation method and calculating the acoustic power level for a single side. The DS-0225 measurement procedure is omitted. This method does not conform to ISO or JIS standards due to two reasons: 1. The frequency range is narrow, and 2. The microphones are not arranged in a face-to-face configuration. For measurements conforming to ISO and JIS standards, please refer to the following catalogs, etc.
DS-0234 Acoustic Power Measurement (SI Method) System
■ Formula for calculating sound power level
The sound source is enclosed by a closed surface, creating a virtual surface that serves as the measurement surface. This surface is further divided, and the acoustic intensity data (I i) is measured at each point. From this data, the acoustic power level (L W) can be calculated using the following formula. With the DS-0225, the frequency band is set when creating trace data, so the calculated acoustic power represents the acoustic power in that frequency band.
Here,
| <ii> </i | : Acoustic intensity component perpendicular to the i-th surface element on the measurement surface |
| Si | : Area of the i-th face element |
| N | : Number of face elements |
| P0 | : Reference sound power (= 10⁻¹² W) |
The diagram below illustrates a single-surface measurement.
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■ Operating Procedure
Import trace data into Excel.
1-1 After data acquisition, click the "Trace Processing" button to open the trace processing screen.
1-2 On the trace screen, set the upper and lower frequency limits and run the trace, and the trace will run automatically.
A TXT file containing the data will be created.
The image below shows the trace execution process in Trace 5.
1-3 The diagram below shows the trace data in a TXT file within the project name folder at the time of data acquisition.
This shows that the file "TRC05.TXT" has been created.
1-4 Open the file in Microsoft Excel. The image below shows what happens when you open "TRC05.TXT".
It shows
Import trace data into Excel.
The figure below shows the calculation after extracting the Z-axis from the trace data imported into Excel. In the calculation formula, Ii is the Z-axis intensity LIN value (W/ m²). If the area per measurement point is Si = 0.1 m × 0.1 m = 0.01 m², the sound power level in a certain frequency band (in this example, 475 Hz to 797.5 Hz: see (1-2)) can be calculated as LW = 36.6 dB. The TXT data contains the value of "AI - Z :TOTAL =" in Σ Ii, but this is excluded from the calculation. The value of "Σ Ii * Si" is the same as "(value of AI - Z :TOTAL) × Si" if Si is the same for all values.
[Calculation Notes]
- If the value of Ii is negative, it remains a negative value (" Ii * Si").
We calculate "Σ I i * S i".
- "I i * Si" and "ΣI i * Si" represent the sound power level (W: power) of that area, and are meaningful values. Therefore, "Σ I i * Si / Po" is calculated last.
- If the values of "I i * S i" and "ΣI i * S i / P o" are negative, it means the sound source is in a different location, and the measurement needs to be reviewed. Also, if the values remain negative, an error will occur in logarithmic calculations.
Last updated: 2009-03-16