Troubleshooting the Audio Quality Test (Windows Embedded CE 6.0)
1/6/2010
Applies to Windows Embedded CE 6.0 R2
Audio quality tests are affected by many factors, both internal and external to the audio system. To isolate the cause of a problem, you must carefully examine both the test data and the device itself.
When you troubleshoot audio quality problems, remember that development boards and other prototype hardware might not be engineered to meet RFI or EMI constraints. Such hardware might be too noisy to pass the audio quality test.
Analyzing Test Data
Look for the following patterns in noise data to find common problems:
- If the device uses AC power, the noise-floor might show spikes around 60 Hz (50 Hz in Europe and Asia) and odd-numbered multiples thereof, for example at 180Hz, 300Hz. The most common cause is power-line rectification noise.
- A high noise-floor across the spectrum often results from measurement hardware that relies exclusively on digital gain. Instead of reducing the amplitude of the samples, reduce the power or input of the amplifier gain.
- Significant harmonic distortion (THD) and inter-modulation products frequently result from pushing an output amplifier to a point of saturation.
Common Solutions
Consider the following steps for solving audio quality problems:
- Eliminate clock or PWM signals from nearby motors
- Check for incorrect grounding in the lab
- Replace low-quality or unshielded cable with high-quality, shielded cable
- Verify audio component configuration
- Contact with the hardware vendor or internal hardware engineers