AN93
Rev. 1.4
291
Audio-Recording Pitfalls
To facilitate communications protocol debugging, it is imperative that audio recordings be made properly. The two
most common conditions that degrade the quality of audio recordings are:
"Waveform clipping due to excessive recording level
"Time-varying levels due to use of AGC (automatic gain control)
Figure 59. Recording Made at Excessive Level
The above recording was made at an excessively high level. One can see clipping in the time domain and
numerous distortion products in the frequency domain.
Figure 60. Recording Made with AGC Noise Reduction
The above recording was made with AGC "Noise Reduction" still enabled, as can be seen from the gradual level
drop in the time domain graph at the start of V.22 negotiations. It also shows evidence of a microphone being used
instead of the Radio Shack adapter. This is visible in the frequency-domain graph as horizontal striations (an
undulating frequency response) during the scrambled portion of the V.22 communication. One can also see third-
harmonic distortion.
Summary of Contents for Si2404
Page 2: ...AN93 2 Rev 1 4 ...
Page 200: ...AN93 200 Rev 1 4 Figure 31 TAM Handset and Speakerphone Voice Paths ...
Page 201: ...AN93 Rev 1 4 201 Figure 32 Si3000 Codec Gain and Signal Selection Options ...
Page 290: ...AN93 290 Rev 1 4 Figure 57 256 Band Spectral Display Figure 58 2048 Band Spectral Display ...
Page 305: ...AN93 Rev 1 4 305 Figure 76 Parallel or SPI Port Interrupt Service Flowchart ...