Denoiser

The Denoiser eliminates or reduces any noise below a threshold volume level. The Denoiser uses fast Fourier transform (FFT) analysis to recognize frequency bands of lower volume and less complex harmonic structure. It then reduces these low-level, less complex bands to the desired dB level.

If you use the Denoiser too aggressively, however, the algorithm produces artifacts, which are usually less desirable than the existing noise. If using the Denoiser produces these artifacts, you can use the three Smoothing knobs to reduce or eliminate them.

Figure. Denoiser window.

Denoiser Main Parameters

The Denoiser offers the following main parameters:

Figure. Main parameters.
  • Threshold slider and field: Sets the threshold level. Signals that fall below this level are reduced by the Denoiser.
  • Reduce slider and field: Sets the amount of noise reduction applied to signals that fall below the threshold. When reducing noise, remember that each 6 dB reduction is equivalent to halving the volume level (and each 6 dB increase equals a doubling of the volume level).

    Note: If the noise floor of your recording is very high (more than -68 dB), reducing it to a level of -83 to -78 dB should be sufficient, provided this doesn’t introduce any audible side effects. This effectively reduces the noise by more than 10 dB, to less than half of the original (noise) volume.

  • Noise Type slider and field: Determines the type of noise that you want to reduce.
    • A value of 0 equals white noise (equal frequency distribution).

    • Positive values change the noise type to pink noise (harmonic noise; greater bass response).

    • Negative values change the noise type to blue noise (hissy tape noise).

  • Graphical display: Shows how the lowest volume levels of your audio material—which should be mostly, or entirely, noise—are reduced. Changes to parameters are instantly reflected here, so keep an eye on it.

Denoiser Smoothing Parameters

The Denoiser offers the following smoothing parameters:

Figure. Smoothing parameters.
  • Frequency knob and field: Adjusts how smoothing is applied to neighboring frequencies. If the Denoiser recognizes that only noise is present on a certain frequency band, the higher you set the Frequency parameter, the more it changes the neighboring frequency bands to avoid glass noise.
  • Time knob and field: Sets the time required by the Denoiser to reach (or release) maximum reduction. This is the simplest form of smoothing.
  • Transition knob and field: Adjusts how smoothing is applied to neighboring volume levels. If the Denoiser recognizes that only noise is present in a certain volume range, the higher you set the Transition parameter, the more similar-level values are changed, in order to avoid glass noise.

Using the Denoiser

The following steps are recommended for using the Denoiser effect.

To use the Denoiser
  1. Locate a section of the audio where only noise is audible, and set the Threshold value so that only signals at, or below, this level are filtered out.

  2. Play the audio signal and set the Reduce value to the point where noise reduction is optimal but little of the desired signal is reduced.

  3. If you encounter artifacts, use the smoothing parameters.