Learn Music and Audio Production | iZotope Tips and Tutorials
How to Clean Up Audio from a Phone Recording
Description:
Recordings made off of a telephone line can be heavily distorted and difficult to understand. The De-clip module in iZotope’s RX software is designed to help repair analog and digital distortion by redrawing squared-off waveforms.
Sample:
In this phone recording of an interview segment, we can hear significant overmodulation and see the clipped waveforms that square off at 0 dB:
Standalone Workflow
- Open an audio file in the RX Audio Editor or send it using RX Connect.
- Select the distorted portions of the audio, and open the De-clip module.
- For this audio sample, we can start by selecting the preset “Subtle analog clipping.” Click Preview to hear the results.
- Adjust the Threshold sliders to the right of the Histogram or Spectrogram to tailor the settings to your audio, or click Suggest to have the De-clip module analyze your audio and set the threshold automatically. For this example, any Threshold setting above –1.0 will work fine, so we don’t need to adjust the Threshold slider.
- Once you’ve found the desired settings, click Process to repair your audio.
- Use the Dialogue De-noise plug-in to remove the remaining hiss from the recording. For more information on removing background hiss, follow the recommendations in the recipe for Repairing Noisy Vocal and Instrument Tracks.
- Phone lines are usually band limited to a range of 300 Hz to 4 kHz. There can be certain frequencies in this region that resonate because of this. Try using the Corrective EQ module to notch out these resonant frequencies and improve intelligibility
Plug-in Workflow
- Select the distorted portions of the audio and open the RX De-clip plug-in.
- Select a preset from the drop down menu, or set the threshold manually to identify where the De-clip algorithm should begin processing. For this example, the default threshold of –1.0 dB worked well.
- Click Preview to hear the results. Adjust the threshold and quality settings as necessary.
- Once you’ve found the desired settings, click the Process or Render button to complete the repair.
- Use the Dialogue De-noise plug-in to remove the remaining hiss from the recording. For more information on removing background hiss, follow the recommendations in the recipe for Repairing Noisy Vocal and Instrument Tracks.
- Phone lines are usually band limited to a range of 300 Hz to 4 kHz. There can be certain frequencies in this region that resonate because of this. Try using an EQ plug-in to notch out these resonant frequencies and improve intelligibility