REW进行声卡校准(Soundcard Calibration)

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前置阅读：

在用REW进行正式测量之前要进行校准，前面讲了如何进行声压校准，现在讲声卡校准(Soundcard Calibration)。

打开软件，进入设置（Preferences）界面，找到声卡校准选项(Soundcard Calibration)。

点击校准声卡(Soundcard Calibration)，下面的帮助（Help）界面出现提示：

The audio interface is measured with an external loopback connected to allow its frequency response to be determined and saved as a calibration file. This response is subtracted when subsequent measurements are made, eliminating the interface's own response. The loopback connection goes from the output channel that will be used for measurement (usually the Right channel of the Line output) to the input channel that will be used (usually the Right channel of the line input). Please connect the loopback now and press Next when it has been connected or Cancel to quit.

音频接口在外部环路连接的情况下进行测量，以确定其频率响应并保存为校准文件。当进行后续测量时，此响应被减去，从而消除了接口自身的响应的影响。环路连接将用于测量的输出通道（通常是线路输出的右通道）与使用的输入通道（通常是线路输入的右通道）对接。请现在确认环路连接后按下一步，或取消退出。

注：所谓环路连接（loopback connected），就是将用于测量的输入和输出通道对接。

环路连接后，点击下一步(Next>)：

The first stage is to use a 1kHz tone to set the levels of the measurement signal and the interface input volume. The tone is generated at the current Sweep Level setting, it is best to use a fairly high level for interface measurement, between -12 and -6 dBFS. Set this level now using the Sweep Level control above, the original level will be restored at the end. If the REW volume controls are available and enabled the Output Volume should be around 0.5 if it affects the signal level. If REW volume controls are not available or not being used set the levels via the controls in your interface's mixer or your OS audio control panel.

Press Next when the Sweep Level and Output Volume have been set or Cancel to quit.

第一阶段是使用频率为1kHz的信号来设置测量信号的电平和接口输入音量。此频率是在当前的扫描电平设置下生成的，最好使用一个相当高的电平进行接口测量，建议在-12和-6 dBFS之间。现在使用上面的扫频电平控制设置此项，原来的设置将在完成后恢复。如果REW音量控制已启用，可以调节测试信号的电平，使输出音量应在0.5左右。如果REW音量控制不可用或未被启用，请通过电脑界面混音器或操作系统音频控制面板中的控制来设置音量。

当扫频电平和输出音量已设置好后按下一步，或取消退出。

设置好电平后，点击下一步(Next>)，进行电平检测：

The 1kHz tone is now playing. Adjust the Input Volume using the REW control (if enabled and available) or your interface's mixer or your OS audio level controls so that the input level is close to the output level, ideally within 6dB, and the peak level (the red line on the bar) is lower than -1dB. If the input level control is at its maximum but the input level is still more than 6dB below the output level try increasing the Output Volume using the REW control (if enabled and available) or your interface's mixer or your OS audio level controls.

Press Next when the input volume has been set or Cancel to quit.

此时频率为1kHz的信号正在播放。使用REW音量控制选项（如果已启用）或电脑接口的混音器或操作系统音频电平控件调整输入音量，使输入电平接近输出电平，理想情况下在6dB以内，峰值电平（条形图上的红线）低于-1 dB。如果输入电平控制处于最大值，但输入电平仍比输出电平低6dB以上，请尝试使用REW音量控制选项（如果已启用）或电脑接口的混音器或操作系统音频电平控制来增加输出音量。

设置好音量(电平)后按下一步，或取消退出。

可以通过Control output/input wolume音量控制选项，来调整输出和输入通道的电频，此时观察左侧的电平表，使第一根输出（out）和第二根输入（in）电平指示相近。此处也可单独调整电平(Levels)。

电平调整好后点击下一步(Next>)，进行声卡频响曲线测试。

The audio interface can now be measured. Press Next to start the measurement or Cancel to quit. After pressing Next this panel will be minimised and a measurement progress panel will appear. Wait for the measurement to complete, this panel will then be displayed again.

现在可以测量音频接口。按“下一步”开始测量，或按“取消”退出。按下“下一步”后，此面板将被最小化，并显示一个测量进度面板。等待测量完成后，此面板将再次显示。