Bit-Depth Converter

Process Menu

Use the Bit-Depth Converter dialog to convert sound files to different bit depths. To display this dialog, choose Bit-Depth Converter from the Process menu.

Because the signal-to-noise decreases when you decrease the bit depth of a file, you should maximize the volume of the sound file using the Volume or Normalize functions before performing the conversion.

What do you want to do?

Change a file's bit depth

  1. From the Process menu, choose Bit-Depth Converter.

  2. Choose a preset from the Name drop-down list or adjust the controls as desired:

a. Choose a bit-depth from the drop-down list.

Increasing a file's bit-depth cannot improve the quality of the existing audio, but does allow higher resolution for processing.

b. Choose a setting from the Dither drop-down list if you're decreasing the file's bit-depth and want to add dither noise to mask quantization noise. For example, if you want to burn a 24-bit audio file to an audio CD, dithering will produce a cleaner signal than a simple bit-depth conversion.

Setting

Description

Rectangular

Eliminates distortion caused by conversion to a lower bit-depth, but the noise level is dependent on the signal.

Triangular

Eliminates distortion caused by conversion to a lower bit-depth and eliminates noise floor modulation by producing a slightly higher noise level.

Highpass Triangular

Eliminates distortion caused by conversion to a lower bit-depth and eliminates noise floor modulation by producing a slightly higher noise level. Noise is shifted to higher frequencies than standard triangular dithering.

Gaussian

Does not perform as well as rectangular or triangular dithering, but may be suitable for some material.

In general, Highpass Triangular with noise shaping produces the most favorable results.

c. Choose a setting from the Noise shaping drop-down list to apply noise shaping to your signal. Noise shaping lowers the percieved noise floor of the signal by shifting most of the noise into the upper frequencies of human hearing.

Setting

Description

Off

Does not apply noise shaping.

High-Pass Contour

Moves noise into high frequencies.

The frequencies to which the noise is shifted (shaped) are close to the Nyquist frequency, so you should not apply noise shaping to files with a sample rate below 44.1 kHz. For example, a 22 kHz signal has a Nyquist frequency of 11 kHz. If you move most of the noise into that range, you are putting it into a sensitive area of human hearing and will produce a worse-sounding signal.

Equal Loudness Contour

Distributes noise equally into high and low frequencies.

  1. Click OK.

For more information about using processing dialog controls, click here.

Set the bit-depth for playback only

Right click the Sample Size box on the status bar and choose a new bit-depth from the shortcut menu.