Noise Suppressor Expander#
Noise suppressor and expander Stages control the behaviour of quiet signals, typically by tring to reduce the audibility of noise in the signal.
- class audio_dsp.stages.noise_suppressor_expander.NoiseSuppressorExpander(**kwargs)
The Noise Suppressor (Expander) stage. A noise suppressor that reduces the level of an audio signal when it falls below a threshold. This is also known as an expander.
When the signal envelope falls below the threshold, the gain applied to the signal is reduced relative to the expansion ratio over the release time. When the envelope returns above the threshold, the gain applied to the signal is increased to 1 over the attack time.
The initial state of the noise suppressor is with the suppression off; this models a full scale signal having been present before t = 0.
- Attributes:
- dsp_block
audio_dsp.dsp.drc.expander.noise_suppressor_expander
The DSP block class; see Noise Suppressor/Expander for implementation details.
- dsp_block
- make_noise_suppressor_expander(ratio, threshold_db, attack_t, release_t, Q_sig=27)
Update noise suppressor (expander) configuration based on new parameters.
All parameters are passed to the constructor of
audio_dsp.dsp.drc.noise_suppressor_expander
.- Parameters:
- ratiofloat
The expansion ratio applied to the signal when the envelope falls below the threshold.
- threshold_dbfloat
The threshold level in decibels below which the audio signal is attenuated.
- attack_tfloat
Attack time of the noise suppressor in seconds.
- release_tfloat
Release time of the noise suppressor in seconds.
Control
The following runtime control parameters are available for the NoiseSuppressorExpander Stage:
Command ID macro |
Payload length |
Description |
---|---|---|
CMD_NOISE_SUPPRESSOR_EXPANDER_ATTACK_ALPHA |
|
The attack alpha in Q0.31 format. |
CMD_NOISE_SUPPRESSOR_EXPANDER_RELEASE_ALPHA |
|
The release alpha in Q0.31 format. |
CMD_NOISE_SUPPRESSOR_EXPANDER_ENVELOPE |
|
The current peak envelope of the signal in Q_SIG format. |
CMD_NOISE_SUPPRESSOR_EXPANDER_THRESHOLD |
|
The threshold in Q_SIG format below which suppression will occur. |
CMD_NOISE_SUPPRESSOR_EXPANDER_GAIN |
|
The current gain applied by the noise suppressor in Q0.31 format. |
CMD_NOISE_SUPPRESSOR_EXPANDER_SLOPE |
|
The expansion slope of the noise suppressor. This is calculated as (1 - ratio). |