Rew acoustic test (II): offline test

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During the smart speaker speaker test , Because the smart speaker has an independent chip module , Therefore, it is not practical to connect the equipment to be tested to the test system . Usually, the Bluetooth module of the intelligent speaker is connected to the Bluetooth module of the test system to play the signal , however demo The smart speaker at this stage may not have Bluetooth module , In these cases , It can be done by putting REW The test signal of is saved as wav file , Use adb Command import , Use aplay/tinyplay Command to play the test signal , Then you can go to REW To generate a new test curve . This is it. REW Offline test function of .

1. Test sweep signal

Test sweep signal （measurement sweep signal） yes REW A special signal used in measuring system response .

It includes a logarithmic scan from the start frequency to the end frequency .

The scan duration is set using the length control . If the starting frequency is lower than 20Hz, Then the signal from DC To 10Hz Start linear scan , Then perform logarithmic scanning from there to the end frequency .

The test sweep signal can be saved to WAV File for offline testing . Be careful , The test sweep signal may be in different REW Changes between versions , Therefore, always use the current version of REW The generated sweep signal is used for frequency response analysis .

2. Generate test sweep signal

The first step is to generate a sweep test signal , Play the signal during frequency response test . It is from 【 Signal generator 】 Module generated .

It is recommended to use timing reference signal for off-line test . Set scan and timing reference trim （ Usually fine tune to zero ） Signal level , And select the sampling rate for generating the scanning signal - This should be the same sampling rate as the recorded response , Or an integral multiple or fraction of the recording rate . If the system you are testing supports , Please select 32 Bit floating point as WAV Sampling resolution , If not , Please try 24 position .

3. Import sweep recording

Use 「 file 」 Menu 「 Import sweep recording 」 entry （ Or use Ctrl+Shift+N Shortcut ） open “ Import ” Dialog box .

First, import the measurement sweep file , Or browse to the file location , Or drag it to Stimulus window . Select the channel to import ,1 It's the left channel ,2 Right channel . If in REW mic/meter And the current... Specified in the sound card preferences mic And sound card cal The file should be applied to the file to be imported （ for example , If calibrated mic Recording , also mic cal The file is loaded in REW in ）, Please select 「 application cal file 」 box . Display the image of signal waveform . After that, the signal waveform image of the imported file will appear .

Then import the recording file . Browse the file or drag the file into the response window . If there are multiple response records , You can drag them all into the response window at once , Each response record generates a separate measurement result . If the recorded sampling rate is an integral multiple or fraction of the measured swept sampling rate , Before processing , The recording will be resampled to match the scan rate .

The test results of offline tests can be displayed in the same way as any other test REW Various processes are carried out in . The test comment includes the file name used to generate it , The default test name is the file name of the recording .