VoIP Acoustic Design - VLSI Solution
VoIP Acoustic Design - VLSI Solution
VoIP Acoustic Design - VLSI Solution
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<strong>VLSI</strong><strong>Solution</strong>y<strong>VoIP</strong> <strong>Acoustic</strong> <strong>Design</strong>VSMPGHHTable of Contents1 Introduction 42 How to Combat Feedback 52.1 What Feedback Is . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52.2 Feedback Mechanisms in <strong>VoIP</strong> Speaker Phone Demonstration Unit . . . . 62.3 Case Study: Feedback in an Actual Product . . . . . . . . . . . . . . . . . 72.3.1 The Product . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72.3.2 Measurement Methodology . . . . . . . . . . . . . . . . . . . . . . 82.3.3 Reference 0.0 dB: <strong>VLSI</strong> <strong>Solution</strong>’s Demonstration Board . . . . . . 92.3.4 Meas +30.5 dB: As Is . . . . . . . . . . . . . . . . . . . . . . . . . 102.3.5 Meas +16.0 dB: No Chassis . . . . . . . . . . . . . . . . . . . . . . 112.3.6 Meas +28.5 dB: Speaker Padding . . . . . . . . . . . . . . . . . . . 122.3.7 Meas +27.6 dB: Padding around Microphone Circuit Board . . . . 132.3.8 Meas +21.8 dB: Mic Removed from Circuit Board . . . . . . . . . 142.3.9 Meas +16.2 dB: Mic Removed from Circ. Board + Chassis Hole . 152.3.10 Meas +15.8 dB: Microphone Glued to Chassis . . . . . . . . . . . . 162.3.11 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173 Pass-Through <strong>VoIP</strong> Software 183.1 What the Software Does . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183.2 How to Load the Software . . . . . . . . . . . . . . . . . . . . . . . . . . . 194 Document Version History 215 Contact Information 22Rev. 2.11 2008-09-18 Page 2(22)
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