With the thread on the Motorola part on how to get the best audio on various Motorola radios, I figured I'd post the same here. These are settings based on the TM9100 series and may differ slightly.

In the radio software, go to Channel Setup -> Channels -> Advanced. The good side is that these can be set PER CHANNEL in the radio. The bad side is that they need to be set PER CHANNEL.

Screenshot:
audio_options.png

From the Tait Documentation:
Automatic Noise Reduction
Enables the automatic noise reduction feature on the channel. Automatic noise reduction reduces the gain when the radio receives a low-level signal. This allows improvements in audio quality by reducing noise usually heard during pauses in conversation. You cannot enable both Automatic Noise Reduction and Companding. This field is only relevant for Analog receptions on the channel. Select or clear the check box.

Extended ALC

Enables extended automatic level control (ALC) on the channel, which increases the sensitivity of the microphone. This setting is only effective when the radio receives digital transmissions.

Companding
Enables audio companding (compression and expansion) on the channel. Companding compresses the signal as it is transmitted, and expands the signal to its original level when received. This process improves the overall signal-to-noise ratio, and can improve the desired audio under marginal conditions such as when there is a lot of background noise. You cannot enable both Companding and Automatic Noise Reduction. This field is only relevant for analog transmissions and receptions on the channel. Select or clear the check box.

Now in my experimentation, some of these bits of information are dead wrong. You can have Automatic Noise Reduction enabled OR Companding. The Extended ALC may be enabled or disabled independently of the other two settings.

NOTE: These options appear to affect INCOMING received audio as well. As such, the best feature combination I have found has been Automatic Noise Reduction ON, Extended ALC ON.

Companding seems to have strange 'artefacts' on received audio on analog transmissions that my brain had difficulty deciphering. This seems particularly apparent on weak to moderate signal levels.

Happy audio tweaking